| /* |
| * fs/dcache.c |
| * |
| * Complete reimplementation |
| * (C) 1997 Thomas Schoebel-Theuer, |
| * with heavy changes by Linus Torvalds |
| */ |
| |
| /* |
| * Notes on the allocation strategy: |
| * |
| * The dcache is a master of the icache - whenever a dcache entry |
| * exists, the inode will always exist. "iput()" is done either when |
| * the dcache entry is deleted or garbage collected. |
| */ |
| |
| #include <linux/ratelimit.h> |
| #include <linux/string.h> |
| #include <linux/mm.h> |
| #include <linux/fs.h> |
| #include <linux/fsnotify.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/hash.h> |
| #include <linux/cache.h> |
| #include <linux/export.h> |
| #include <linux/security.h> |
| #include <linux/seqlock.h> |
| #include <linux/bootmem.h> |
| #include <linux/bit_spinlock.h> |
| #include <linux/rculist_bl.h> |
| #include <linux/list_lru.h> |
| #include "internal.h" |
| #include "mount.h" |
| |
| /* |
| * Usage: |
| * dcache->d_inode->i_lock protects: |
| * - i_dentry, d_u.d_alias, d_inode of aliases |
| * dcache_hash_bucket lock protects: |
| * - the dcache hash table |
| * s_roots bl list spinlock protects: |
| * - the s_roots list (see __d_drop) |
| * dentry->d_sb->s_dentry_lru_lock protects: |
| * - the dcache lru lists and counters |
| * d_lock protects: |
| * - d_flags |
| * - d_name |
| * - d_lru |
| * - d_count |
| * - d_unhashed() |
| * - d_parent and d_subdirs |
| * - childrens' d_child and d_parent |
| * - d_u.d_alias, d_inode |
| * |
| * Ordering: |
| * dentry->d_inode->i_lock |
| * dentry->d_lock |
| * dentry->d_sb->s_dentry_lru_lock |
| * dcache_hash_bucket lock |
| * s_roots lock |
| * |
| * If there is an ancestor relationship: |
| * dentry->d_parent->...->d_parent->d_lock |
| * ... |
| * dentry->d_parent->d_lock |
| * dentry->d_lock |
| * |
| * If no ancestor relationship: |
| * arbitrary, since it's serialized on rename_lock |
| */ |
| int sysctl_vfs_cache_pressure __read_mostly = 100; |
| EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); |
| |
| __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); |
| |
| EXPORT_SYMBOL(rename_lock); |
| |
| static struct kmem_cache *dentry_cache __read_mostly; |
| |
| const struct qstr empty_name = QSTR_INIT("", 0); |
| EXPORT_SYMBOL(empty_name); |
| const struct qstr slash_name = QSTR_INIT("/", 1); |
| EXPORT_SYMBOL(slash_name); |
| |
| /* |
| * This is the single most critical data structure when it comes |
| * to the dcache: the hashtable for lookups. Somebody should try |
| * to make this good - I've just made it work. |
| * |
| * This hash-function tries to avoid losing too many bits of hash |
| * information, yet avoid using a prime hash-size or similar. |
| */ |
| |
| static unsigned int d_hash_shift __read_mostly; |
| |
| static struct hlist_bl_head *dentry_hashtable __read_mostly; |
| |
| static inline struct hlist_bl_head *d_hash(unsigned int hash) |
| { |
| return dentry_hashtable + (hash >> d_hash_shift); |
| } |
| |
| #define IN_LOOKUP_SHIFT 10 |
| static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT]; |
| |
| static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent, |
| unsigned int hash) |
| { |
| hash += (unsigned long) parent / L1_CACHE_BYTES; |
| return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT); |
| } |
| |
| |
| /* Statistics gathering. */ |
| struct dentry_stat_t dentry_stat = { |
| .age_limit = 45, |
| }; |
| |
| static DEFINE_PER_CPU(long, nr_dentry); |
| static DEFINE_PER_CPU(long, nr_dentry_unused); |
| |
| #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) |
| |
| /* |
| * Here we resort to our own counters instead of using generic per-cpu counters |
| * for consistency with what the vfs inode code does. We are expected to harvest |
| * better code and performance by having our own specialized counters. |
| * |
| * Please note that the loop is done over all possible CPUs, not over all online |
| * CPUs. The reason for this is that we don't want to play games with CPUs going |
| * on and off. If one of them goes off, we will just keep their counters. |
| * |
| * glommer: See cffbc8a for details, and if you ever intend to change this, |
| * please update all vfs counters to match. |
| */ |
| static long get_nr_dentry(void) |
| { |
| int i; |
| long sum = 0; |
| for_each_possible_cpu(i) |
| sum += per_cpu(nr_dentry, i); |
| return sum < 0 ? 0 : sum; |
| } |
| |
| static long get_nr_dentry_unused(void) |
| { |
| int i; |
| long sum = 0; |
| for_each_possible_cpu(i) |
| sum += per_cpu(nr_dentry_unused, i); |
| return sum < 0 ? 0 : sum; |
| } |
| |
| int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| dentry_stat.nr_dentry = get_nr_dentry(); |
| dentry_stat.nr_unused = get_nr_dentry_unused(); |
| return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| } |
| #endif |
| |
| /* |
| * Compare 2 name strings, return 0 if they match, otherwise non-zero. |
| * The strings are both count bytes long, and count is non-zero. |
| */ |
| #ifdef CONFIG_DCACHE_WORD_ACCESS |
| |
| #include <asm/word-at-a-time.h> |
| /* |
| * NOTE! 'cs' and 'scount' come from a dentry, so it has a |
| * aligned allocation for this particular component. We don't |
| * strictly need the load_unaligned_zeropad() safety, but it |
| * doesn't hurt either. |
| * |
| * In contrast, 'ct' and 'tcount' can be from a pathname, and do |
| * need the careful unaligned handling. |
| */ |
| static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
| { |
| unsigned long a,b,mask; |
| |
| for (;;) { |
| a = read_word_at_a_time(cs); |
| b = load_unaligned_zeropad(ct); |
| if (tcount < sizeof(unsigned long)) |
| break; |
| if (unlikely(a != b)) |
| return 1; |
| cs += sizeof(unsigned long); |
| ct += sizeof(unsigned long); |
| tcount -= sizeof(unsigned long); |
| if (!tcount) |
| return 0; |
| } |
| mask = bytemask_from_count(tcount); |
| return unlikely(!!((a ^ b) & mask)); |
| } |
| |
| #else |
| |
| static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
| { |
| do { |
| if (*cs != *ct) |
| return 1; |
| cs++; |
| ct++; |
| tcount--; |
| } while (tcount); |
| return 0; |
| } |
| |
| #endif |
| |
| static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount) |
| { |
| /* |
| * Be careful about RCU walk racing with rename: |
| * use 'READ_ONCE' to fetch the name pointer. |
| * |
| * NOTE! Even if a rename will mean that the length |
| * was not loaded atomically, we don't care. The |
| * RCU walk will check the sequence count eventually, |
| * and catch it. And we won't overrun the buffer, |
| * because we're reading the name pointer atomically, |
| * and a dentry name is guaranteed to be properly |
| * terminated with a NUL byte. |
| * |
| * End result: even if 'len' is wrong, we'll exit |
| * early because the data cannot match (there can |
| * be no NUL in the ct/tcount data) |
| */ |
| const unsigned char *cs = READ_ONCE(dentry->d_name.name); |
| |
| return dentry_string_cmp(cs, ct, tcount); |
| } |
| |
| struct external_name { |
| union { |
| atomic_t count; |
| struct rcu_head head; |
| } u; |
| unsigned char name[]; |
| }; |
| |
| static inline struct external_name *external_name(struct dentry *dentry) |
| { |
| return container_of(dentry->d_name.name, struct external_name, name[0]); |
| } |
| |
| static void __d_free(struct rcu_head *head) |
| { |
| struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
| |
| kmem_cache_free(dentry_cache, dentry); |
| } |
| |
| static void __d_free_external_name(struct rcu_head *head) |
| { |
| struct external_name *name = container_of(head, struct external_name, |
| u.head); |
| |
| mod_node_page_state(page_pgdat(virt_to_page(name)), |
| NR_INDIRECTLY_RECLAIMABLE_BYTES, |
| -ksize(name)); |
| |
| kfree(name); |
| } |
| |
| static void __d_free_external(struct rcu_head *head) |
| { |
| struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
| |
| __d_free_external_name(&external_name(dentry)->u.head); |
| |
| kmem_cache_free(dentry_cache, dentry); |
| } |
| |
| static inline int dname_external(const struct dentry *dentry) |
| { |
| return dentry->d_name.name != dentry->d_iname; |
| } |
| |
| void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry) |
| { |
| spin_lock(&dentry->d_lock); |
| if (unlikely(dname_external(dentry))) { |
| struct external_name *p = external_name(dentry); |
| atomic_inc(&p->u.count); |
| spin_unlock(&dentry->d_lock); |
| name->name = p->name; |
| } else { |
| memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN); |
| spin_unlock(&dentry->d_lock); |
| name->name = name->inline_name; |
| } |
| } |
| EXPORT_SYMBOL(take_dentry_name_snapshot); |
| |
| void release_dentry_name_snapshot(struct name_snapshot *name) |
| { |
| if (unlikely(name->name != name->inline_name)) { |
| struct external_name *p; |
| p = container_of(name->name, struct external_name, name[0]); |
| if (unlikely(atomic_dec_and_test(&p->u.count))) |
| call_rcu(&p->u.head, __d_free_external_name); |
| } |
| } |
| EXPORT_SYMBOL(release_dentry_name_snapshot); |
| |
| static inline void __d_set_inode_and_type(struct dentry *dentry, |
| struct inode *inode, |
| unsigned type_flags) |
| { |
| unsigned flags; |
| |
| dentry->d_inode = inode; |
| flags = READ_ONCE(dentry->d_flags); |
| flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU); |
| flags |= type_flags; |
| WRITE_ONCE(dentry->d_flags, flags); |
| } |
| |
| static inline void __d_clear_type_and_inode(struct dentry *dentry) |
| { |
| unsigned flags = READ_ONCE(dentry->d_flags); |
| |
| flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU); |
| WRITE_ONCE(dentry->d_flags, flags); |
| dentry->d_inode = NULL; |
| } |
| |
| static void dentry_free(struct dentry *dentry) |
| { |
| WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias)); |
| if (unlikely(dname_external(dentry))) { |
| struct external_name *p = external_name(dentry); |
| if (likely(atomic_dec_and_test(&p->u.count))) { |
| call_rcu(&dentry->d_u.d_rcu, __d_free_external); |
| return; |
| } |
| } |
| /* if dentry was never visible to RCU, immediate free is OK */ |
| if (!(dentry->d_flags & DCACHE_RCUACCESS)) |
| __d_free(&dentry->d_u.d_rcu); |
| else |
| call_rcu(&dentry->d_u.d_rcu, __d_free); |
| } |
| |
| /* |
| * Release the dentry's inode, using the filesystem |
| * d_iput() operation if defined. |
| */ |
| static void dentry_unlink_inode(struct dentry * dentry) |
| __releases(dentry->d_lock) |
| __releases(dentry->d_inode->i_lock) |
| { |
| struct inode *inode = dentry->d_inode; |
| |
| raw_write_seqcount_begin(&dentry->d_seq); |
| __d_clear_type_and_inode(dentry); |
| hlist_del_init(&dentry->d_u.d_alias); |
| raw_write_seqcount_end(&dentry->d_seq); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| if (!inode->i_nlink) |
| fsnotify_inoderemove(inode); |
| if (dentry->d_op && dentry->d_op->d_iput) |
| dentry->d_op->d_iput(dentry, inode); |
| else |
| iput(inode); |
| } |
| |
| /* |
| * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry |
| * is in use - which includes both the "real" per-superblock |
| * LRU list _and_ the DCACHE_SHRINK_LIST use. |
| * |
| * The DCACHE_SHRINK_LIST bit is set whenever the dentry is |
| * on the shrink list (ie not on the superblock LRU list). |
| * |
| * The per-cpu "nr_dentry_unused" counters are updated with |
| * the DCACHE_LRU_LIST bit. |
| * |
| * These helper functions make sure we always follow the |
| * rules. d_lock must be held by the caller. |
| */ |
| #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x)) |
| static void d_lru_add(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, 0); |
| dentry->d_flags |= DCACHE_LRU_LIST; |
| this_cpu_inc(nr_dentry_unused); |
| WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
| } |
| |
| static void d_lru_del(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags &= ~DCACHE_LRU_LIST; |
| this_cpu_dec(nr_dentry_unused); |
| WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
| } |
| |
| static void d_shrink_del(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
| list_del_init(&dentry->d_lru); |
| dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
| this_cpu_dec(nr_dentry_unused); |
| } |
| |
| static void d_shrink_add(struct dentry *dentry, struct list_head *list) |
| { |
| D_FLAG_VERIFY(dentry, 0); |
| list_add(&dentry->d_lru, list); |
| dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST; |
| this_cpu_inc(nr_dentry_unused); |
| } |
| |
| /* |
| * These can only be called under the global LRU lock, ie during the |
| * callback for freeing the LRU list. "isolate" removes it from the |
| * LRU lists entirely, while shrink_move moves it to the indicated |
| * private list. |
| */ |
| static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags &= ~DCACHE_LRU_LIST; |
| this_cpu_dec(nr_dentry_unused); |
| list_lru_isolate(lru, &dentry->d_lru); |
| } |
| |
| static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry, |
| struct list_head *list) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags |= DCACHE_SHRINK_LIST; |
| list_lru_isolate_move(lru, &dentry->d_lru, list); |
| } |
| |
| /** |
| * d_drop - drop a dentry |
| * @dentry: dentry to drop |
| * |
| * d_drop() unhashes the entry from the parent dentry hashes, so that it won't |
| * be found through a VFS lookup any more. Note that this is different from |
| * deleting the dentry - d_delete will try to mark the dentry negative if |
| * possible, giving a successful _negative_ lookup, while d_drop will |
| * just make the cache lookup fail. |
| * |
| * d_drop() is used mainly for stuff that wants to invalidate a dentry for some |
| * reason (NFS timeouts or autofs deletes). |
| * |
| * __d_drop requires dentry->d_lock |
| * ___d_drop doesn't mark dentry as "unhashed" |
| * (dentry->d_hash.pprev will be LIST_POISON2, not NULL). |
| */ |
| static void ___d_drop(struct dentry *dentry) |
| { |
| struct hlist_bl_head *b; |
| /* |
| * Hashed dentries are normally on the dentry hashtable, |
| * with the exception of those newly allocated by |
| * d_obtain_root, which are always IS_ROOT: |
| */ |
| if (unlikely(IS_ROOT(dentry))) |
| b = &dentry->d_sb->s_roots; |
| else |
| b = d_hash(dentry->d_name.hash); |
| |
| hlist_bl_lock(b); |
| __hlist_bl_del(&dentry->d_hash); |
| hlist_bl_unlock(b); |
| } |
| |
| void __d_drop(struct dentry *dentry) |
| { |
| if (!d_unhashed(dentry)) { |
| ___d_drop(dentry); |
| dentry->d_hash.pprev = NULL; |
| write_seqcount_invalidate(&dentry->d_seq); |
| } |
| } |
| EXPORT_SYMBOL(__d_drop); |
| |
| void d_drop(struct dentry *dentry) |
| { |
| spin_lock(&dentry->d_lock); |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| } |
| EXPORT_SYMBOL(d_drop); |
| |
| static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent) |
| { |
| struct dentry *next; |
| /* |
| * Inform d_walk() and shrink_dentry_list() that we are no longer |
| * attached to the dentry tree |
| */ |
| dentry->d_flags |= DCACHE_DENTRY_KILLED; |
| if (unlikely(list_empty(&dentry->d_child))) |
| return; |
| __list_del_entry(&dentry->d_child); |
| /* |
| * Cursors can move around the list of children. While we'd been |
| * a normal list member, it didn't matter - ->d_child.next would've |
| * been updated. However, from now on it won't be and for the |
| * things like d_walk() it might end up with a nasty surprise. |
| * Normally d_walk() doesn't care about cursors moving around - |
| * ->d_lock on parent prevents that and since a cursor has no children |
| * of its own, we get through it without ever unlocking the parent. |
| * There is one exception, though - if we ascend from a child that |
| * gets killed as soon as we unlock it, the next sibling is found |
| * using the value left in its ->d_child.next. And if _that_ |
| * pointed to a cursor, and cursor got moved (e.g. by lseek()) |
| * before d_walk() regains parent->d_lock, we'll end up skipping |
| * everything the cursor had been moved past. |
| * |
| * Solution: make sure that the pointer left behind in ->d_child.next |
| * points to something that won't be moving around. I.e. skip the |
| * cursors. |
| */ |
| while (dentry->d_child.next != &parent->d_subdirs) { |
| next = list_entry(dentry->d_child.next, struct dentry, d_child); |
| if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR))) |
| break; |
| dentry->d_child.next = next->d_child.next; |
| } |
| } |
| |
| static void __dentry_kill(struct dentry *dentry) |
| { |
| struct dentry *parent = NULL; |
| bool can_free = true; |
| if (!IS_ROOT(dentry)) |
| parent = dentry->d_parent; |
| |
| /* |
| * The dentry is now unrecoverably dead to the world. |
| */ |
| lockref_mark_dead(&dentry->d_lockref); |
| |
| /* |
| * inform the fs via d_prune that this dentry is about to be |
| * unhashed and destroyed. |
| */ |
| if (dentry->d_flags & DCACHE_OP_PRUNE) |
| dentry->d_op->d_prune(dentry); |
| |
| if (dentry->d_flags & DCACHE_LRU_LIST) { |
| if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) |
| d_lru_del(dentry); |
| } |
| /* if it was on the hash then remove it */ |
| __d_drop(dentry); |
| dentry_unlist(dentry, parent); |
| if (parent) |
| spin_unlock(&parent->d_lock); |
| if (dentry->d_inode) |
| dentry_unlink_inode(dentry); |
| else |
| spin_unlock(&dentry->d_lock); |
| this_cpu_dec(nr_dentry); |
| if (dentry->d_op && dentry->d_op->d_release) |
| dentry->d_op->d_release(dentry); |
| |
| spin_lock(&dentry->d_lock); |
| if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
| dentry->d_flags |= DCACHE_MAY_FREE; |
| can_free = false; |
| } |
| spin_unlock(&dentry->d_lock); |
| if (likely(can_free)) |
| dentry_free(dentry); |
| cond_resched(); |
| } |
| |
| static struct dentry *__lock_parent(struct dentry *dentry) |
| { |
| struct dentry *parent; |
| rcu_read_lock(); |
| spin_unlock(&dentry->d_lock); |
| again: |
| parent = READ_ONCE(dentry->d_parent); |
| spin_lock(&parent->d_lock); |
| /* |
| * We can't blindly lock dentry until we are sure |
| * that we won't violate the locking order. |
| * Any changes of dentry->d_parent must have |
| * been done with parent->d_lock held, so |
| * spin_lock() above is enough of a barrier |
| * for checking if it's still our child. |
| */ |
| if (unlikely(parent != dentry->d_parent)) { |
| spin_unlock(&parent->d_lock); |
| goto again; |
| } |
| rcu_read_unlock(); |
| if (parent != dentry) |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| else |
| parent = NULL; |
| return parent; |
| } |
| |
| static inline struct dentry *lock_parent(struct dentry *dentry) |
| { |
| struct dentry *parent = dentry->d_parent; |
| if (IS_ROOT(dentry)) |
| return NULL; |
| if (likely(spin_trylock(&parent->d_lock))) |
| return parent; |
| return __lock_parent(dentry); |
| } |
| |
| static inline bool retain_dentry(struct dentry *dentry) |
| { |
| WARN_ON(d_in_lookup(dentry)); |
| |
| /* Unreachable? Get rid of it */ |
| if (unlikely(d_unhashed(dentry))) |
| return false; |
| |
| if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) |
| return false; |
| |
| if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) { |
| if (dentry->d_op->d_delete(dentry)) |
| return false; |
| } |
| /* retain; LRU fodder */ |
| dentry->d_lockref.count--; |
| if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) |
| d_lru_add(dentry); |
| else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED))) |
| dentry->d_flags |= DCACHE_REFERENCED; |
| return true; |
| } |
| |
| /* |
| * Finish off a dentry we've decided to kill. |
| * dentry->d_lock must be held, returns with it unlocked. |
| * Returns dentry requiring refcount drop, or NULL if we're done. |
| */ |
| static struct dentry *dentry_kill(struct dentry *dentry) |
| __releases(dentry->d_lock) |
| { |
| struct inode *inode = dentry->d_inode; |
| struct dentry *parent = NULL; |
| |
| if (inode && unlikely(!spin_trylock(&inode->i_lock))) |
| goto slow_positive; |
| |
| if (!IS_ROOT(dentry)) { |
| parent = dentry->d_parent; |
| if (unlikely(!spin_trylock(&parent->d_lock))) { |
| parent = __lock_parent(dentry); |
| if (likely(inode || !dentry->d_inode)) |
| goto got_locks; |
| /* negative that became positive */ |
| if (parent) |
| spin_unlock(&parent->d_lock); |
| inode = dentry->d_inode; |
| goto slow_positive; |
| } |
| } |
| __dentry_kill(dentry); |
| return parent; |
| |
| slow_positive: |
| spin_unlock(&dentry->d_lock); |
| spin_lock(&inode->i_lock); |
| spin_lock(&dentry->d_lock); |
| parent = lock_parent(dentry); |
| got_locks: |
| if (unlikely(dentry->d_lockref.count != 1)) { |
| dentry->d_lockref.count--; |
| } else if (likely(!retain_dentry(dentry))) { |
| __dentry_kill(dentry); |
| return parent; |
| } |
| /* we are keeping it, after all */ |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| if (parent) |
| spin_unlock(&parent->d_lock); |
| spin_unlock(&dentry->d_lock); |
| return NULL; |
| } |
| |
| /* |
| * Try to do a lockless dput(), and return whether that was successful. |
| * |
| * If unsuccessful, we return false, having already taken the dentry lock. |
| * |
| * The caller needs to hold the RCU read lock, so that the dentry is |
| * guaranteed to stay around even if the refcount goes down to zero! |
| */ |
| static inline bool fast_dput(struct dentry *dentry) |
| { |
| int ret; |
| unsigned int d_flags; |
| |
| /* |
| * If we have a d_op->d_delete() operation, we sould not |
| * let the dentry count go to zero, so use "put_or_lock". |
| */ |
| if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) |
| return lockref_put_or_lock(&dentry->d_lockref); |
| |
| /* |
| * .. otherwise, we can try to just decrement the |
| * lockref optimistically. |
| */ |
| ret = lockref_put_return(&dentry->d_lockref); |
| |
| /* |
| * If the lockref_put_return() failed due to the lock being held |
| * by somebody else, the fast path has failed. We will need to |
| * get the lock, and then check the count again. |
| */ |
| if (unlikely(ret < 0)) { |
| spin_lock(&dentry->d_lock); |
| if (dentry->d_lockref.count > 1) { |
| dentry->d_lockref.count--; |
| spin_unlock(&dentry->d_lock); |
| return 1; |
| } |
| return 0; |
| } |
| |
| /* |
| * If we weren't the last ref, we're done. |
| */ |
| if (ret) |
| return 1; |
| |
| /* |
| * Careful, careful. The reference count went down |
| * to zero, but we don't hold the dentry lock, so |
| * somebody else could get it again, and do another |
| * dput(), and we need to not race with that. |
| * |
| * However, there is a very special and common case |
| * where we don't care, because there is nothing to |
| * do: the dentry is still hashed, it does not have |
| * a 'delete' op, and it's referenced and already on |
| * the LRU list. |
| * |
| * NOTE! Since we aren't locked, these values are |
| * not "stable". However, it is sufficient that at |
| * some point after we dropped the reference the |
| * dentry was hashed and the flags had the proper |
| * value. Other dentry users may have re-gotten |
| * a reference to the dentry and change that, but |
| * our work is done - we can leave the dentry |
| * around with a zero refcount. |
| */ |
| smp_rmb(); |
| d_flags = READ_ONCE(dentry->d_flags); |
| d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED; |
| |
| /* Nothing to do? Dropping the reference was all we needed? */ |
| if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry)) |
| return 1; |
| |
| /* |
| * Not the fast normal case? Get the lock. We've already decremented |
| * the refcount, but we'll need to re-check the situation after |
| * getting the lock. |
| */ |
| spin_lock(&dentry->d_lock); |
| |
| /* |
| * Did somebody else grab a reference to it in the meantime, and |
| * we're no longer the last user after all? Alternatively, somebody |
| * else could have killed it and marked it dead. Either way, we |
| * don't need to do anything else. |
| */ |
| if (dentry->d_lockref.count) { |
| spin_unlock(&dentry->d_lock); |
| return 1; |
| } |
| |
| /* |
| * Re-get the reference we optimistically dropped. We hold the |
| * lock, and we just tested that it was zero, so we can just |
| * set it to 1. |
| */ |
| dentry->d_lockref.count = 1; |
| return 0; |
| } |
| |
| |
| /* |
| * This is dput |
| * |
| * This is complicated by the fact that we do not want to put |
| * dentries that are no longer on any hash chain on the unused |
| * list: we'd much rather just get rid of them immediately. |
| * |
| * However, that implies that we have to traverse the dentry |
| * tree upwards to the parents which might _also_ now be |
| * scheduled for deletion (it may have been only waiting for |
| * its last child to go away). |
| * |
| * This tail recursion is done by hand as we don't want to depend |
| * on the compiler to always get this right (gcc generally doesn't). |
| * Real recursion would eat up our stack space. |
| */ |
| |
| /* |
| * dput - release a dentry |
| * @dentry: dentry to release |
| * |
| * Release a dentry. This will drop the usage count and if appropriate |
| * call the dentry unlink method as well as removing it from the queues and |
| * releasing its resources. If the parent dentries were scheduled for release |
| * they too may now get deleted. |
| */ |
| void dput(struct dentry *dentry) |
| { |
| while (dentry) { |
| might_sleep(); |
| |
| rcu_read_lock(); |
| if (likely(fast_dput(dentry))) { |
| rcu_read_unlock(); |
| return; |
| } |
| |
| /* Slow case: now with the dentry lock held */ |
| rcu_read_unlock(); |
| |
| if (likely(retain_dentry(dentry))) { |
| spin_unlock(&dentry->d_lock); |
| return; |
| } |
| |
| dentry = dentry_kill(dentry); |
| } |
| } |
| EXPORT_SYMBOL(dput); |
| |
| |
| /* This must be called with d_lock held */ |
| static inline void __dget_dlock(struct dentry *dentry) |
| { |
| dentry->d_lockref.count++; |
| } |
| |
| static inline void __dget(struct dentry *dentry) |
| { |
| lockref_get(&dentry->d_lockref); |
| } |
| |
| struct dentry *dget_parent(struct dentry *dentry) |
| { |
| int gotref; |
| struct dentry *ret; |
| |
| /* |
| * Do optimistic parent lookup without any |
| * locking. |
| */ |
| rcu_read_lock(); |
| ret = READ_ONCE(dentry->d_parent); |
| gotref = lockref_get_not_zero(&ret->d_lockref); |
| rcu_read_unlock(); |
| if (likely(gotref)) { |
| if (likely(ret == READ_ONCE(dentry->d_parent))) |
| return ret; |
| dput(ret); |
| } |
| |
| repeat: |
| /* |
| * Don't need rcu_dereference because we re-check it was correct under |
| * the lock. |
| */ |
| rcu_read_lock(); |
| ret = dentry->d_parent; |
| spin_lock(&ret->d_lock); |
| if (unlikely(ret != dentry->d_parent)) { |
| spin_unlock(&ret->d_lock); |
| rcu_read_unlock(); |
| goto repeat; |
| } |
| rcu_read_unlock(); |
| BUG_ON(!ret->d_lockref.count); |
| ret->d_lockref.count++; |
| spin_unlock(&ret->d_lock); |
| return ret; |
| } |
| EXPORT_SYMBOL(dget_parent); |
| |
| static struct dentry * __d_find_any_alias(struct inode *inode) |
| { |
| struct dentry *alias; |
| |
| if (hlist_empty(&inode->i_dentry)) |
| return NULL; |
| alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias); |
| __dget(alias); |
| return alias; |
| } |
| |
| /** |
| * d_find_any_alias - find any alias for a given inode |
| * @inode: inode to find an alias for |
| * |
| * If any aliases exist for the given inode, take and return a |
| * reference for one of them. If no aliases exist, return %NULL. |
| */ |
| struct dentry *d_find_any_alias(struct inode *inode) |
| { |
| struct dentry *de; |
| |
| spin_lock(&inode->i_lock); |
| de = __d_find_any_alias(inode); |
| spin_unlock(&inode->i_lock); |
| return de; |
| } |
| EXPORT_SYMBOL(d_find_any_alias); |
| |
| /** |
| * d_find_alias - grab a hashed alias of inode |
| * @inode: inode in question |
| * |
| * If inode has a hashed alias, or is a directory and has any alias, |
| * acquire the reference to alias and return it. Otherwise return NULL. |
| * Notice that if inode is a directory there can be only one alias and |
| * it can be unhashed only if it has no children, or if it is the root |
| * of a filesystem, or if the directory was renamed and d_revalidate |
| * was the first vfs operation to notice. |
| * |
| * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer |
| * any other hashed alias over that one. |
| */ |
| static struct dentry *__d_find_alias(struct inode *inode) |
| { |
| struct dentry *alias; |
| |
| if (S_ISDIR(inode->i_mode)) |
| return __d_find_any_alias(inode); |
| |
| hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { |
| spin_lock(&alias->d_lock); |
| if (!d_unhashed(alias)) { |
| __dget_dlock(alias); |
| spin_unlock(&alias->d_lock); |
| return alias; |
| } |
| spin_unlock(&alias->d_lock); |
| } |
| return NULL; |
| } |
| |
| struct dentry *d_find_alias(struct inode *inode) |
| { |
| struct dentry *de = NULL; |
| |
| if (!hlist_empty(&inode->i_dentry)) { |
| spin_lock(&inode->i_lock); |
| de = __d_find_alias(inode); |
| spin_unlock(&inode->i_lock); |
| } |
| return de; |
| } |
| EXPORT_SYMBOL(d_find_alias); |
| |
| /* |
| * Try to kill dentries associated with this inode. |
| * WARNING: you must own a reference to inode. |
| */ |
| void d_prune_aliases(struct inode *inode) |
| { |
| struct dentry *dentry; |
| restart: |
| spin_lock(&inode->i_lock); |
| hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) { |
| spin_lock(&dentry->d_lock); |
| if (!dentry->d_lockref.count) { |
| struct dentry *parent = lock_parent(dentry); |
| if (likely(!dentry->d_lockref.count)) { |
| __dentry_kill(dentry); |
| dput(parent); |
| goto restart; |
| } |
| if (parent) |
| spin_unlock(&parent->d_lock); |
| } |
| spin_unlock(&dentry->d_lock); |
| } |
| spin_unlock(&inode->i_lock); |
| } |
| EXPORT_SYMBOL(d_prune_aliases); |
| |
| /* |
| * Lock a dentry from shrink list. |
| * Called under rcu_read_lock() and dentry->d_lock; the former |
| * guarantees that nothing we access will be freed under us. |
| * Note that dentry is *not* protected from concurrent dentry_kill(), |
| * d_delete(), etc. |
| * |
| * Return false if dentry has been disrupted or grabbed, leaving |
| * the caller to kick it off-list. Otherwise, return true and have |
| * that dentry's inode and parent both locked. |
| */ |
| static bool shrink_lock_dentry(struct dentry *dentry) |
| { |
| struct inode *inode; |
| struct dentry *parent; |
| |
| if (dentry->d_lockref.count) |
| return false; |
| |
| inode = dentry->d_inode; |
| if (inode && unlikely(!spin_trylock(&inode->i_lock))) { |
| spin_unlock(&dentry->d_lock); |
| spin_lock(&inode->i_lock); |
| spin_lock(&dentry->d_lock); |
| if (unlikely(dentry->d_lockref.count)) |
| goto out; |
| /* changed inode means that somebody had grabbed it */ |
| if (unlikely(inode != dentry->d_inode)) |
| goto out; |
| } |
| |
| parent = dentry->d_parent; |
| if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock))) |
| return true; |
| |
| spin_unlock(&dentry->d_lock); |
| spin_lock(&parent->d_lock); |
| if (unlikely(parent != dentry->d_parent)) { |
| spin_unlock(&parent->d_lock); |
| spin_lock(&dentry->d_lock); |
| goto out; |
| } |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| if (likely(!dentry->d_lockref.count)) |
| return true; |
| spin_unlock(&parent->d_lock); |
| out: |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| return false; |
| } |
| |
| static void shrink_dentry_list(struct list_head *list) |
| { |
| while (!list_empty(list)) { |
| struct dentry *dentry, *parent; |
| |
| dentry = list_entry(list->prev, struct dentry, d_lru); |
| spin_lock(&dentry->d_lock); |
| rcu_read_lock(); |
| if (!shrink_lock_dentry(dentry)) { |
| bool can_free = false; |
| rcu_read_unlock(); |
| d_shrink_del(dentry); |
| if (dentry->d_lockref.count < 0) |
| can_free = dentry->d_flags & DCACHE_MAY_FREE; |
| spin_unlock(&dentry->d_lock); |
| if (can_free) |
| dentry_free(dentry); |
| continue; |
| } |
| rcu_read_unlock(); |
| d_shrink_del(dentry); |
| parent = dentry->d_parent; |
| __dentry_kill(dentry); |
| if (parent == dentry) |
| continue; |
| /* |
| * We need to prune ancestors too. This is necessary to prevent |
| * quadratic behavior of shrink_dcache_parent(), but is also |
| * expected to be beneficial in reducing dentry cache |
| * fragmentation. |
| */ |
| dentry = parent; |
| while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) |
| dentry = dentry_kill(dentry); |
| } |
| } |
| |
| static enum lru_status dentry_lru_isolate(struct list_head *item, |
| struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) |
| { |
| struct list_head *freeable = arg; |
| struct dentry *dentry = container_of(item, struct dentry, d_lru); |
| |
| |
| /* |
| * we are inverting the lru lock/dentry->d_lock here, |
| * so use a trylock. If we fail to get the lock, just skip |
| * it |
| */ |
| if (!spin_trylock(&dentry->d_lock)) |
| return LRU_SKIP; |
| |
| /* |
| * Referenced dentries are still in use. If they have active |
| * counts, just remove them from the LRU. Otherwise give them |
| * another pass through the LRU. |
| */ |
| if (dentry->d_lockref.count) { |
| d_lru_isolate(lru, dentry); |
| spin_unlock(&dentry->d_lock); |
| return LRU_REMOVED; |
| } |
| |
| if (dentry->d_flags & DCACHE_REFERENCED) { |
| dentry->d_flags &= ~DCACHE_REFERENCED; |
| spin_unlock(&dentry->d_lock); |
| |
| /* |
| * The list move itself will be made by the common LRU code. At |
| * this point, we've dropped the dentry->d_lock but keep the |
| * lru lock. This is safe to do, since every list movement is |
| * protected by the lru lock even if both locks are held. |
| * |
| * This is guaranteed by the fact that all LRU management |
| * functions are intermediated by the LRU API calls like |
| * list_lru_add and list_lru_del. List movement in this file |
| * only ever occur through this functions or through callbacks |
| * like this one, that are called from the LRU API. |
| * |
| * The only exceptions to this are functions like |
| * shrink_dentry_list, and code that first checks for the |
| * DCACHE_SHRINK_LIST flag. Those are guaranteed to be |
| * operating only with stack provided lists after they are |
| * properly isolated from the main list. It is thus, always a |
| * local access. |
| */ |
| return LRU_ROTATE; |
| } |
| |
| d_lru_shrink_move(lru, dentry, freeable); |
| spin_unlock(&dentry->d_lock); |
| |
| return LRU_REMOVED; |
| } |
| |
| /** |
| * prune_dcache_sb - shrink the dcache |
| * @sb: superblock |
| * @sc: shrink control, passed to list_lru_shrink_walk() |
| * |
| * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This |
| * is done when we need more memory and called from the superblock shrinker |
| * function. |
| * |
| * This function may fail to free any resources if all the dentries are in |
| * use. |
| */ |
| long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc) |
| { |
| LIST_HEAD(dispose); |
| long freed; |
| |
| freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc, |
| dentry_lru_isolate, &dispose); |
| shrink_dentry_list(&dispose); |
| return freed; |
| } |
| |
| static enum lru_status dentry_lru_isolate_shrink(struct list_head *item, |
| struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) |
| { |
| struct list_head *freeable = arg; |
| struct dentry *dentry = container_of(item, struct dentry, d_lru); |
| |
| /* |
| * we are inverting the lru lock/dentry->d_lock here, |
| * so use a trylock. If we fail to get the lock, just skip |
| * it |
| */ |
| if (!spin_trylock(&dentry->d_lock)) |
| return LRU_SKIP; |
| |
| d_lru_shrink_move(lru, dentry, freeable); |
| spin_unlock(&dentry->d_lock); |
| |
| return LRU_REMOVED; |
| } |
| |
| |
| /** |
| * shrink_dcache_sb - shrink dcache for a superblock |
| * @sb: superblock |
| * |
| * Shrink the dcache for the specified super block. This is used to free |
| * the dcache before unmounting a file system. |
| */ |
| void shrink_dcache_sb(struct super_block *sb) |
| { |
| long freed; |
| |
| do { |
| LIST_HEAD(dispose); |
| |
| freed = list_lru_walk(&sb->s_dentry_lru, |
| dentry_lru_isolate_shrink, &dispose, 1024); |
| |
| this_cpu_sub(nr_dentry_unused, freed); |
| shrink_dentry_list(&dispose); |
| } while (list_lru_count(&sb->s_dentry_lru) > 0); |
| } |
| EXPORT_SYMBOL(shrink_dcache_sb); |
| |
| /** |
| * enum d_walk_ret - action to talke during tree walk |
| * @D_WALK_CONTINUE: contrinue walk |
| * @D_WALK_QUIT: quit walk |
| * @D_WALK_NORETRY: quit when retry is needed |
| * @D_WALK_SKIP: skip this dentry and its children |
| */ |
| enum d_walk_ret { |
| D_WALK_CONTINUE, |
| D_WALK_QUIT, |
| D_WALK_NORETRY, |
| D_WALK_SKIP, |
| }; |
| |
| /** |
| * d_walk - walk the dentry tree |
| * @parent: start of walk |
| * @data: data passed to @enter() and @finish() |
| * @enter: callback when first entering the dentry |
| * |
| * The @enter() callbacks are called with d_lock held. |
| */ |
| static void d_walk(struct dentry *parent, void *data, |
| enum d_walk_ret (*enter)(void *, struct dentry *)) |
| { |
| struct dentry *this_parent; |
| struct list_head *next; |
| unsigned seq = 0; |
| enum d_walk_ret ret; |
| bool retry = true; |
| |
| again: |
| read_seqbegin_or_lock(&rename_lock, &seq); |
| this_parent = parent; |
| spin_lock(&this_parent->d_lock); |
| |
| ret = enter(data, this_parent); |
| switch (ret) { |
| case D_WALK_CONTINUE: |
| break; |
| case D_WALK_QUIT: |
| case D_WALK_SKIP: |
| goto out_unlock; |
| case D_WALK_NORETRY: |
| retry = false; |
| break; |
| } |
| repeat: |
| next = this_parent->d_subdirs.next; |
| resume: |
| while (next != &this_parent->d_subdirs) { |
| struct list_head *tmp = next; |
| struct dentry *dentry = list_entry(tmp, struct dentry, d_child); |
| next = tmp->next; |
| |
| if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR)) |
| continue; |
| |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| |
| ret = enter(data, dentry); |
| switch (ret) { |
| case D_WALK_CONTINUE: |
| break; |
| case D_WALK_QUIT: |
| spin_unlock(&dentry->d_lock); |
| goto out_unlock; |
| case D_WALK_NORETRY: |
| retry = false; |
| break; |
| case D_WALK_SKIP: |
| spin_unlock(&dentry->d_lock); |
| continue; |
| } |
| |
| if (!list_empty(&dentry->d_subdirs)) { |
| spin_unlock(&this_parent->d_lock); |
| spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); |
| this_parent = dentry; |
| spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
| goto repeat; |
| } |
| spin_unlock(&dentry->d_lock); |
| } |
| /* |
| * All done at this level ... ascend and resume the search. |
| */ |
| rcu_read_lock(); |
| ascend: |
| if (this_parent != parent) { |
| struct dentry *child = this_parent; |
| this_parent = child->d_parent; |
| |
| spin_unlock(&child->d_lock); |
| spin_lock(&this_parent->d_lock); |
| |
| /* might go back up the wrong parent if we have had a rename. */ |
| if (need_seqretry(&rename_lock, seq)) |
| goto rename_retry; |
| /* go into the first sibling still alive */ |
| do { |
| next = child->d_child.next; |
| if (next == &this_parent->d_subdirs) |
| goto ascend; |
| child = list_entry(next, struct dentry, d_child); |
| } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)); |
| rcu_read_unlock(); |
| goto resume; |
| } |
| if (need_seqretry(&rename_lock, seq)) |
| goto rename_retry; |
| rcu_read_unlock(); |
| |
| out_unlock: |
| spin_unlock(&this_parent->d_lock); |
| done_seqretry(&rename_lock, seq); |
| return; |
| |
| rename_retry: |
| spin_unlock(&this_parent->d_lock); |
| rcu_read_unlock(); |
| BUG_ON(seq & 1); |
| if (!retry) |
| return; |
| seq = 1; |
| goto again; |
| } |
| |
| struct check_mount { |
| struct vfsmount *mnt; |
| unsigned int mounted; |
| }; |
| |
| static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry) |
| { |
| struct check_mount *info = data; |
| struct path path = { .mnt = info->mnt, .dentry = dentry }; |
| |
| if (likely(!d_mountpoint(dentry))) |
| return D_WALK_CONTINUE; |
| if (__path_is_mountpoint(&path)) { |
| info->mounted = 1; |
| return D_WALK_QUIT; |
| } |
| return D_WALK_CONTINUE; |
| } |
| |
| /** |
| * path_has_submounts - check for mounts over a dentry in the |
| * current namespace. |
| * @parent: path to check. |
| * |
| * Return true if the parent or its subdirectories contain |
| * a mount point in the current namespace. |
| */ |
| int path_has_submounts(const struct path *parent) |
| { |
| struct check_mount data = { .mnt = parent->mnt, .mounted = 0 }; |
| |
| read_seqlock_excl(&mount_lock); |
| d_walk(parent->dentry, &data, path_check_mount); |
| read_sequnlock_excl(&mount_lock); |
| |
| return data.mounted; |
| } |
| EXPORT_SYMBOL(path_has_submounts); |
| |
| /* |
| * Called by mount code to set a mountpoint and check if the mountpoint is |
| * reachable (e.g. NFS can unhash a directory dentry and then the complete |
| * subtree can become unreachable). |
| * |
| * Only one of d_invalidate() and d_set_mounted() must succeed. For |
| * this reason take rename_lock and d_lock on dentry and ancestors. |
| */ |
| int d_set_mounted(struct dentry *dentry) |
| { |
| struct dentry *p; |
| int ret = -ENOENT; |
| write_seqlock(&rename_lock); |
| for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) { |
| /* Need exclusion wrt. d_invalidate() */ |
| spin_lock(&p->d_lock); |
| if (unlikely(d_unhashed(p))) { |
| spin_unlock(&p->d_lock); |
| goto out; |
| } |
| spin_unlock(&p->d_lock); |
| } |
| spin_lock(&dentry->d_lock); |
| if (!d_unlinked(dentry)) { |
| ret = -EBUSY; |
| if (!d_mountpoint(dentry)) { |
| dentry->d_flags |= DCACHE_MOUNTED; |
| ret = 0; |
| } |
| } |
| spin_unlock(&dentry->d_lock); |
| out: |
| write_sequnlock(&rename_lock); |
| return ret; |
| } |
| |
| /* |
| * Search the dentry child list of the specified parent, |
| * and move any unused dentries to the end of the unused |
| * list for prune_dcache(). We descend to the next level |
| * whenever the d_subdirs list is non-empty and continue |
| * searching. |
| * |
| * It returns zero iff there are no unused children, |
| * otherwise it returns the number of children moved to |
| * the end of the unused list. This may not be the total |
| * number of unused children, because select_parent can |
| * drop the lock and return early due to latency |
| * constraints. |
| */ |
| |
| struct select_data { |
| struct dentry *start; |
| struct list_head dispose; |
| int found; |
| }; |
| |
| static enum d_walk_ret select_collect(void *_data, struct dentry *dentry) |
| { |
| struct select_data *data = _data; |
| enum d_walk_ret ret = D_WALK_CONTINUE; |
| |
| if (data->start == dentry) |
| goto out; |
| |
| if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
| data->found++; |
| } else { |
| if (dentry->d_flags & DCACHE_LRU_LIST) |
| d_lru_del(dentry); |
| if (!dentry->d_lockref.count) { |
| d_shrink_add(dentry, &data->dispose); |
| data->found++; |
| } |
| } |
| /* |
| * We can return to the caller if we have found some (this |
| * ensures forward progress). We'll be coming back to find |
| * the rest. |
| */ |
| if (!list_empty(&data->dispose)) |
| ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY; |
| out: |
| return ret; |
| } |
| |
| /** |
| * shrink_dcache_parent - prune dcache |
| * @parent: parent of entries to prune |
| * |
| * Prune the dcache to remove unused children of the parent dentry. |
| */ |
| void shrink_dcache_parent(struct dentry *parent) |
| { |
| for (;;) { |
| struct select_data data; |
| |
| INIT_LIST_HEAD(&data.dispose); |
| data.start = parent; |
| data.found = 0; |
| |
| d_walk(parent, &data, select_collect); |
| |
| if (!list_empty(&data.dispose)) { |
| shrink_dentry_list(&data.dispose); |
| continue; |
| } |
| |
| cond_resched(); |
| if (!data.found) |
| break; |
| } |
| } |
| EXPORT_SYMBOL(shrink_dcache_parent); |
| |
| static enum d_walk_ret umount_check(void *_data, struct dentry *dentry) |
| { |
| /* it has busy descendents; complain about those instead */ |
| if (!list_empty(&dentry->d_subdirs)) |
| return D_WALK_CONTINUE; |
| |
| /* root with refcount 1 is fine */ |
| if (dentry == _data && dentry->d_lockref.count == 1) |
| return D_WALK_CONTINUE; |
| |
| printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} " |
| " still in use (%d) [unmount of %s %s]\n", |
| dentry, |
| dentry->d_inode ? |
| dentry->d_inode->i_ino : 0UL, |
| dentry, |
| dentry->d_lockref.count, |
| dentry->d_sb->s_type->name, |
| dentry->d_sb->s_id); |
| WARN_ON(1); |
| return D_WALK_CONTINUE; |
| } |
| |
| static void do_one_tree(struct dentry *dentry) |
| { |
| shrink_dcache_parent(dentry); |
| d_walk(dentry, dentry, umount_check); |
| d_drop(dentry); |
| dput(dentry); |
| } |
| |
| /* |
| * destroy the dentries attached to a superblock on unmounting |
| */ |
| void shrink_dcache_for_umount(struct super_block *sb) |
| { |
| struct dentry *dentry; |
| |
| WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked"); |
| |
| dentry = sb->s_root; |
| sb->s_root = NULL; |
| do_one_tree(dentry); |
| |
| while (!hlist_bl_empty(&sb->s_roots)) { |
| dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash)); |
| do_one_tree(dentry); |
| } |
| } |
| |
| static enum d_walk_ret find_submount(void *_data, struct dentry *dentry) |
| { |
| struct dentry **victim = _data; |
| if (d_mountpoint(dentry)) { |
| __dget_dlock(dentry); |
| *victim = dentry; |
| return D_WALK_QUIT; |
| } |
| return D_WALK_CONTINUE; |
| } |
| |
| /** |
| * d_invalidate - detach submounts, prune dcache, and drop |
| * @dentry: dentry to invalidate (aka detach, prune and drop) |
| */ |
| void d_invalidate(struct dentry *dentry) |
| { |
| bool had_submounts = false; |
| spin_lock(&dentry->d_lock); |
| if (d_unhashed(dentry)) { |
| spin_unlock(&dentry->d_lock); |
| return; |
| } |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| |
| /* Negative dentries can be dropped without further checks */ |
| if (!dentry->d_inode) |
| return; |
| |
| shrink_dcache_parent(dentry); |
| for (;;) { |
| struct dentry *victim = NULL; |
| d_walk(dentry, &victim, find_submount); |
| if (!victim) { |
| if (had_submounts) |
| shrink_dcache_parent(dentry); |
| return; |
| } |
| had_submounts = true; |
| detach_mounts(victim); |
| dput(victim); |
| } |
| } |
| EXPORT_SYMBOL(d_invalidate); |
| |
| /** |
| * __d_alloc - allocate a dcache entry |
| * @sb: filesystem it will belong to |
| * @name: qstr of the name |
| * |
| * Allocates a dentry. It returns %NULL if there is insufficient memory |
| * available. On a success the dentry is returned. The name passed in is |
| * copied and the copy passed in may be reused after this call. |
| */ |
| |
| struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) |
| { |
| struct external_name *ext = NULL; |
| struct dentry *dentry; |
| char *dname; |
| int err; |
| |
| dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); |
| if (!dentry) |
| return NULL; |
| |
| /* |
| * We guarantee that the inline name is always NUL-terminated. |
| * This way the memcpy() done by the name switching in rename |
| * will still always have a NUL at the end, even if we might |
| * be overwriting an internal NUL character |
| */ |
| dentry->d_iname[DNAME_INLINE_LEN-1] = 0; |
| if (unlikely(!name)) { |
| name = &slash_name; |
| dname = dentry->d_iname; |
| } else if (name->len > DNAME_INLINE_LEN-1) { |
| size_t size = offsetof(struct external_name, name[1]); |
| |
| ext = kmalloc(size + name->len, GFP_KERNEL_ACCOUNT); |
| if (!ext) { |
| kmem_cache_free(dentry_cache, dentry); |
| return NULL; |
| } |
| atomic_set(&ext->u.count, 1); |
| dname = ext->name; |
| } else { |
| dname = dentry->d_iname; |
| } |
| |
| dentry->d_name.len = name->len; |
| dentry->d_name.hash = name->hash; |
| memcpy(dname, name->name, name->len); |
| dname[name->len] = 0; |
| |
| /* Make sure we always see the terminating NUL character */ |
| smp_store_release(&dentry->d_name.name, dname); /* ^^^ */ |
| |
| dentry->d_lockref.count = 1; |
| dentry->d_flags = 0; |
| spin_lock_init(&dentry->d_lock); |
| seqcount_init(&dentry->d_seq); |
| dentry->d_inode = NULL; |
| dentry->d_parent = dentry; |
| dentry->d_sb = sb; |
| dentry->d_op = NULL; |
| dentry->d_fsdata = NULL; |
| INIT_HLIST_BL_NODE(&dentry->d_hash); |
| INIT_LIST_HEAD(&dentry->d_lru); |
| INIT_LIST_HEAD(&dentry->d_subdirs); |
| INIT_HLIST_NODE(&dentry->d_u.d_alias); |
| INIT_LIST_HEAD(&dentry->d_child); |
| d_set_d_op(dentry, dentry->d_sb->s_d_op); |
| |
| if (dentry->d_op && dentry->d_op->d_init) { |
| err = dentry->d_op->d_init(dentry); |
| if (err) { |
| if (dname_external(dentry)) |
| kfree(external_name(dentry)); |
| kmem_cache_free(dentry_cache, dentry); |
| return NULL; |
| } |
| } |
| |
| if (unlikely(ext)) { |
| pg_data_t *pgdat = page_pgdat(virt_to_page(ext)); |
| mod_node_page_state(pgdat, NR_INDIRECTLY_RECLAIMABLE_BYTES, |
| ksize(ext)); |
| } |
| |
| this_cpu_inc(nr_dentry); |
| |
| return dentry; |
| } |
| |
| /** |
| * d_alloc - allocate a dcache entry |
| * @parent: parent of entry to allocate |
| * @name: qstr of the name |
| * |
| * Allocates a dentry. It returns %NULL if there is insufficient memory |
| * available. On a success the dentry is returned. The name passed in is |
| * copied and the copy passed in may be reused after this call. |
| */ |
| struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) |
| { |
| struct dentry *dentry = __d_alloc(parent->d_sb, name); |
| if (!dentry) |
| return NULL; |
| dentry->d_flags |= DCACHE_RCUACCESS; |
| spin_lock(&parent->d_lock); |
| /* |
| * don't need child lock because it is not subject |
| * to concurrency here |
| */ |
| __dget_dlock(parent); |
| dentry->d_parent = parent; |
| list_add(&dentry->d_child, &parent->d_subdirs); |
| spin_unlock(&parent->d_lock); |
| |
| return dentry; |
| } |
| EXPORT_SYMBOL(d_alloc); |
| |
| struct dentry *d_alloc_anon(struct super_block *sb) |
| { |
| return __d_alloc(sb, NULL); |
| } |
| EXPORT_SYMBOL(d_alloc_anon); |
| |
| struct dentry *d_alloc_cursor(struct dentry * parent) |
| { |
| struct dentry *dentry = d_alloc_anon(parent->d_sb); |
| if (dentry) { |
| dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR; |
| dentry->d_parent = dget(parent); |
| } |
| return dentry; |
| } |
| |
| /** |
| * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems) |
| * @sb: the superblock |
| * @name: qstr of the name |
| * |
| * For a filesystem that just pins its dentries in memory and never |
| * performs lookups at all, return an unhashed IS_ROOT dentry. |
| */ |
| struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) |
| { |
| return __d_alloc(sb, name); |
| } |
| EXPORT_SYMBOL(d_alloc_pseudo); |
| |
| struct dentry *d_alloc_name(struct dentry *parent, const char *name) |
| { |
| struct qstr q; |
| |
| q.name = name; |
| q.hash_len = hashlen_string(parent, name); |
| return d_alloc(parent, &q); |
| } |
| EXPORT_SYMBOL(d_alloc_name); |
| |
| void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) |
| { |
| WARN_ON_ONCE(dentry->d_op); |
| WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | |
| DCACHE_OP_COMPARE | |
| DCACHE_OP_REVALIDATE | |
| DCACHE_OP_WEAK_REVALIDATE | |
| DCACHE_OP_DELETE | |
| DCACHE_OP_REAL)); |
| dentry->d_op = op; |
| if (!op) |
| return; |
| if (op->d_hash) |
| dentry->d_flags |= DCACHE_OP_HASH; |
| if (op->d_compare) |
| dentry->d_flags |= DCACHE_OP_COMPARE; |
| if (op->d_revalidate) |
| dentry->d_flags |= DCACHE_OP_REVALIDATE; |
| if (op->d_weak_revalidate) |
| dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE; |
| if (op->d_delete) |
| dentry->d_flags |= DCACHE_OP_DELETE; |
| if (op->d_prune) |
| dentry->d_flags |= DCACHE_OP_PRUNE; |
| if (op->d_real) |
| dentry->d_flags |= DCACHE_OP_REAL; |
| |
| } |
| EXPORT_SYMBOL(d_set_d_op); |
| |
| |
| /* |
| * d_set_fallthru - Mark a dentry as falling through to a lower layer |
| * @dentry - The dentry to mark |
| * |
| * Mark a dentry as falling through to the lower layer (as set with |
| * d_pin_lower()). This flag may be recorded on the medium. |
| */ |
| void d_set_fallthru(struct dentry *dentry) |
| { |
| spin_lock(&dentry->d_lock); |
| dentry->d_flags |= DCACHE_FALLTHRU; |
| spin_unlock(&dentry->d_lock); |
| } |
| EXPORT_SYMBOL(d_set_fallthru); |
| |
| static unsigned d_flags_for_inode(struct inode *inode) |
| { |
| unsigned add_flags = DCACHE_REGULAR_TYPE; |
| |
| if (!inode) |
| return DCACHE_MISS_TYPE; |
| |
| if (S_ISDIR(inode->i_mode)) { |
| add_flags = DCACHE_DIRECTORY_TYPE; |
| if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) { |
| if (unlikely(!inode->i_op->lookup)) |
| add_flags = DCACHE_AUTODIR_TYPE; |
| else |
| inode->i_opflags |= IOP_LOOKUP; |
| } |
| goto type_determined; |
| } |
| |
| if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { |
| if (unlikely(inode->i_op->get_link)) { |
| add_flags = DCACHE_SYMLINK_TYPE; |
| goto type_determined; |
| } |
| inode->i_opflags |= IOP_NOFOLLOW; |
| } |
| |
| if (unlikely(!S_ISREG(inode->i_mode))) |
| add_flags = DCACHE_SPECIAL_TYPE; |
| |
| type_determined: |
| if (unlikely(IS_AUTOMOUNT(inode))) |
| add_flags |= DCACHE_NEED_AUTOMOUNT; |
| return add_flags; |
| } |
| |
| static void __d_instantiate(struct dentry *dentry, struct inode *inode) |
| { |
| unsigned add_flags = d_flags_for_inode(inode); |
| WARN_ON(d_in_lookup(dentry)); |
| |
| spin_lock(&dentry->d_lock); |
| hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
| raw_write_seqcount_begin(&dentry->d_seq); |
| __d_set_inode_and_type(dentry, inode, add_flags); |
| raw_write_seqcount_end(&dentry->d_seq); |
| fsnotify_update_flags(dentry); |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /** |
| * d_instantiate - fill in inode information for a dentry |
| * @entry: dentry to complete |
| * @inode: inode to attach to this dentry |
| * |
| * Fill in inode information in the entry. |
| * |
| * This turns negative dentries into productive full members |
| * of society. |
| * |
| * NOTE! This assumes that the inode count has been incremented |
| * (or otherwise set) by the caller to indicate that it is now |
| * in use by the dcache. |
| */ |
| |
| void d_instantiate(struct dentry *entry, struct inode * inode) |
| { |
| BUG_ON(!hlist_unhashed(&entry->d_u.d_alias)); |
| if (inode) { |
| security_d_instantiate(entry, inode); |
| spin_lock(&inode->i_lock); |
| __d_instantiate(entry, inode); |
| spin_unlock(&inode->i_lock); |
| } |
| } |
| EXPORT_SYMBOL(d_instantiate); |
| |
| /* |
| * This should be equivalent to d_instantiate() + unlock_new_inode(), |
| * with lockdep-related part of unlock_new_inode() done before |
| * anything else. Use that instead of open-coding d_instantiate()/ |
| * unlock_new_inode() combinations. |
| */ |
| void d_instantiate_new(struct dentry *entry, struct inode *inode) |
| { |
| BUG_ON(!hlist_unhashed(&entry->d_u.d_alias)); |
| BUG_ON(!inode); |
| lockdep_annotate_inode_mutex_key(inode); |
| security_d_instantiate(entry, inode); |
| spin_lock(&inode->i_lock); |
| __d_instantiate(entry, inode); |
| WARN_ON(!(inode->i_state & I_NEW)); |
| inode->i_state &= ~I_NEW & ~I_CREATING; |
| smp_mb(); |
| wake_up_bit(&inode->i_state, __I_NEW); |
| spin_unlock(&inode->i_lock); |
| } |
| EXPORT_SYMBOL(d_instantiate_new); |
| |
| struct dentry *d_make_root(struct inode *root_inode) |
| { |
| struct dentry *res = NULL; |
| |
| if (root_inode) { |
| res = d_alloc_anon(root_inode->i_sb); |
| if (res) { |
| res->d_flags |= DCACHE_RCUACCESS; |
| d_instantiate(res, root_inode); |
| } else { |
| iput(root_inode); |
| } |
| } |
| return res; |
| } |
| EXPORT_SYMBOL(d_make_root); |
| |
| static struct dentry *__d_instantiate_anon(struct dentry *dentry, |
| struct inode *inode, |
| bool disconnected) |
| { |
| struct dentry *res; |
| unsigned add_flags; |
| |
| security_d_instantiate(dentry, inode); |
| spin_lock(&inode->i_lock); |
| res = __d_find_any_alias(inode); |
| if (res) { |
| spin_unlock(&inode->i_lock); |
| dput(dentry); |
| goto out_iput; |
| } |
| |
| /* attach a disconnected dentry */ |
| add_flags = d_flags_for_inode(inode); |
| |
| if (disconnected) |
| add_flags |= DCACHE_DISCONNECTED; |
| |
| spin_lock(&dentry->d_lock); |
| __d_set_inode_and_type(dentry, inode, add_flags); |
| hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
| if (!disconnected) { |
| hlist_bl_lock(&dentry->d_sb->s_roots); |
| hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots); |
| hlist_bl_unlock(&dentry->d_sb->s_roots); |
| } |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| |
| return dentry; |
| |
| out_iput: |
| iput(inode); |
| return res; |
| } |
| |
| struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode) |
| { |
| return __d_instantiate_anon(dentry, inode, true); |
| } |
| EXPORT_SYMBOL(d_instantiate_anon); |
| |
| static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected) |
| { |
| struct dentry *tmp; |
| struct dentry *res; |
| |
| if (!inode) |
| return ERR_PTR(-ESTALE); |
| if (IS_ERR(inode)) |
| return ERR_CAST(inode); |
| |
| res = d_find_any_alias(inode); |
| if (res) |
| goto out_iput; |
| |
| tmp = d_alloc_anon(inode->i_sb); |
| if (!tmp) { |
| res = ERR_PTR(-ENOMEM); |
| goto out_iput; |
| } |
| |
| return __d_instantiate_anon(tmp, inode, disconnected); |
| |
| out_iput: |
| iput(inode); |
| return res; |
| } |
| |
| /** |
| * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode |
| * @inode: inode to allocate the dentry for |
| * |
| * Obtain a dentry for an inode resulting from NFS filehandle conversion or |
| * similar open by handle operations. The returned dentry may be anonymous, |
| * or may have a full name (if the inode was already in the cache). |
| * |
| * When called on a directory inode, we must ensure that the inode only ever |
| * has one dentry. If a dentry is found, that is returned instead of |
| * allocating a new one. |
| * |
| * On successful return, the reference to the inode has been transferred |
| * to the dentry. In case of an error the reference on the inode is released. |
| * To make it easier to use in export operations a %NULL or IS_ERR inode may |
| * be passed in and the error will be propagated to the return value, |
| * with a %NULL @inode replaced by ERR_PTR(-ESTALE). |
| */ |
| struct dentry *d_obtain_alias(struct inode *inode) |
| { |
| return __d_obtain_alias(inode, true); |
| } |
| EXPORT_SYMBOL(d_obtain_alias); |
| |
| /** |
| * d_obtain_root - find or allocate a dentry for a given inode |
| * @inode: inode to allocate the dentry for |
| * |
| * Obtain an IS_ROOT dentry for the root of a filesystem. |
| * |
| * We must ensure that directory inodes only ever have one dentry. If a |
| * dentry is found, that is returned instead of allocating a new one. |
| * |
| * On successful return, the reference to the inode has been transferred |
| * to the dentry. In case of an error the reference on the inode is |
| * released. A %NULL or IS_ERR inode may be passed in and will be the |
| * error will be propagate to the return value, with a %NULL @inode |
| * replaced by ERR_PTR(-ESTALE). |
| */ |
| struct dentry *d_obtain_root(struct inode *inode) |
| { |
| return __d_obtain_alias(inode, false); |
| } |
| EXPORT_SYMBOL(d_obtain_root); |
| |
| /** |
| * d_add_ci - lookup or allocate new dentry with case-exact name |
| * @inode: the inode case-insensitive lookup has found |
| * @dentry: the negative dentry that was passed to the parent's lookup func |
| * @name: the case-exact name to be associated with the returned dentry |
| * |
| * This is to avoid filling the dcache with case-insensitive names to the |
| * same inode, only the actual correct case is stored in the dcache for |
| * case-insensitive filesystems. |
| * |
| * For a case-insensitive lookup match and if the the case-exact dentry |
| * already exists in in the dcache, use it and return it. |
| * |
| * If no entry exists with the exact case name, allocate new dentry with |
| * the exact case, and return the spliced entry. |
| */ |
| struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, |
| struct qstr *name) |
| { |
| struct dentry *found, *res; |
| |
| /* |
| * First check if a dentry matching the name already exists, |
| * if not go ahead and create it now. |
| */ |
| found = d_hash_and_lookup(dentry->d_parent, name); |
| if (found) { |
| iput(inode); |
| return found; |
| } |
| if (d_in_lookup(dentry)) { |
| found = d_alloc_parallel(dentry->d_parent, name, |
| dentry->d_wait); |
| if (IS_ERR(found) || !d_in_lookup(found)) { |
| iput(inode); |
| return found; |
| } |
| } else { |
| found = d_alloc(dentry->d_parent, name); |
| if (!found) { |
| iput(inode); |
| return ERR_PTR(-ENOMEM); |
| } |
| } |
| res = d_splice_alias(inode, found); |
| if (res) { |
| dput(found); |
| return res; |
| } |
| return found; |
| } |
| EXPORT_SYMBOL(d_add_ci); |
| |
| |
| static inline bool d_same_name(const struct dentry *dentry, |
| const struct dentry *parent, |
| const struct qstr *name) |
| { |
| if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) { |
| if (dentry->d_name.len != name->len) |
| return false; |
| return dentry_cmp(dentry, name->name, name->len) == 0; |
| } |
| return parent->d_op->d_compare(dentry, |
| dentry->d_name.len, dentry->d_name.name, |
| name) == 0; |
| } |
| |
| /** |
| * __d_lookup_rcu - search for a dentry (racy, store-free) |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * @seqp: returns d_seq value at the point where the dentry was found |
| * Returns: dentry, or NULL |
| * |
| * __d_lookup_rcu is the dcache lookup function for rcu-walk name |
| * resolution (store-free path walking) design described in |
| * Documentation/filesystems/path-lookup.txt. |
| * |
| * This is not to be used outside core vfs. |
| * |
| * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock |
| * held, and rcu_read_lock held. The returned dentry must not be stored into |
| * without taking d_lock and checking d_seq sequence count against @seq |
| * returned here. |
| * |
| * A refcount may be taken on the found dentry with the d_rcu_to_refcount |
| * function. |
| * |
| * Alternatively, __d_lookup_rcu may be called again to look up the child of |
| * the returned dentry, so long as its parent's seqlock is checked after the |
| * child is looked up. Thus, an interlocking stepping of sequence lock checks |
| * is formed, giving integrity down the path walk. |
| * |
| * NOTE! The caller *has* to check the resulting dentry against the sequence |
| * number we've returned before using any of the resulting dentry state! |
| */ |
| struct dentry *__d_lookup_rcu(const struct dentry *parent, |
| const struct qstr *name, |
| unsigned *seqp) |
| { |
| u64 hashlen = name->hash_len; |
| const unsigned char *str = name->name; |
| struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen)); |
| struct hlist_bl_node *node; |
| struct dentry *dentry; |
| |
| /* |
| * Note: There is significant duplication with __d_lookup_rcu which is |
| * required to prevent single threaded performance regressions |
| * especially on architectures where smp_rmb (in seqcounts) are costly. |
| * Keep the two functions in sync. |
| */ |
| |
| /* |
| * The hash list is protected using RCU. |
| * |
| * Carefully use d_seq when comparing a candidate dentry, to avoid |
| * races with d_move(). |
| * |
| * It is possible that concurrent renames can mess up our list |
| * walk here and result in missing our dentry, resulting in the |
| * false-negative result. d_lookup() protects against concurrent |
| * renames using rename_lock seqlock. |
| * |
| * See Documentation/filesystems/path-lookup.txt for more details. |
| */ |
| hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
| unsigned seq; |
| |
| seqretry: |
| /* |
| * The dentry sequence count protects us from concurrent |
| * renames, and thus protects parent and name fields. |
| * |
| * The caller must perform a seqcount check in order |
| * to do anything useful with the returned dentry. |
| * |
| * NOTE! We do a "raw" seqcount_begin here. That means that |
| * we don't wait for the sequence count to stabilize if it |
| * is in the middle of a sequence change. If we do the slow |
| * dentry compare, we will do seqretries until it is stable, |
| * and if we end up with a successful lookup, we actually |
| * want to exit RCU lookup anyway. |
| * |
| * Note that raw_seqcount_begin still *does* smp_rmb(), so |
| * we are still guaranteed NUL-termination of ->d_name.name. |
| */ |
| seq = raw_seqcount_begin(&dentry->d_seq); |
| if (dentry->d_parent != parent) |
| continue; |
| if (d_unhashed(dentry)) |
| continue; |
| |
| if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { |
| int tlen; |
| const char *tname; |
| if (dentry->d_name.hash != hashlen_hash(hashlen)) |
| continue; |
| tlen = dentry->d_name.len; |
| tname = dentry->d_name.name; |
| /* we want a consistent (name,len) pair */ |
| if (read_seqcount_retry(&dentry->d_seq, seq)) { |
| cpu_relax(); |
| goto seqretry; |
| } |
| if (parent->d_op->d_compare(dentry, |
| tlen, tname, name) != 0) |
| continue; |
| } else { |
| if (dentry->d_name.hash_len != hashlen) |
| continue; |
| if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0) |
| continue; |
| } |
| *seqp = seq; |
| return dentry; |
| } |
| return NULL; |
| } |
| |
| /** |
| * d_lookup - search for a dentry |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * Returns: dentry, or NULL |
| * |
| * d_lookup searches the children of the parent dentry for the name in |
| * question. If the dentry is found its reference count is incremented and the |
| * dentry is returned. The caller must use dput to free the entry when it has |
| * finished using it. %NULL is returned if the dentry does not exist. |
| */ |
| struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name) |
| { |
| struct dentry *dentry; |
| unsigned seq; |
| |
| do { |
| seq = read_seqbegin(&rename_lock); |
| dentry = __d_lookup(parent, name); |
| if (dentry) |
| break; |
| } while (read_seqretry(&rename_lock, seq)); |
| return dentry; |
| } |
| EXPORT_SYMBOL(d_lookup); |
| |
| /** |
| * __d_lookup - search for a dentry (racy) |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * Returns: dentry, or NULL |
| * |
| * __d_lookup is like d_lookup, however it may (rarely) return a |
| * false-negative result due to unrelated rename activity. |
| * |
| * __d_lookup is slightly faster by avoiding rename_lock read seqlock, |
| * however it must be used carefully, eg. with a following d_lookup in |
| * the case of failure. |
| * |
| * __d_lookup callers must be commented. |
| */ |
| struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) |
| { |
| unsigned int hash = name->hash; |
| struct hlist_bl_head *b = d_hash(hash); |
| struct hlist_bl_node *node; |
| struct dentry *found = NULL; |
| struct dentry *dentry; |
| |
| /* |
| * Note: There is significant duplication with __d_lookup_rcu which is |
| * required to prevent single threaded performance regressions |
| * especially on architectures where smp_rmb (in seqcounts) are costly. |
| * Keep the two functions in sync. |
| */ |
| |
| /* |
| * The hash list is protected using RCU. |
| * |
| * Take d_lock when comparing a candidate dentry, to avoid races |
| * with d_move(). |
| * |
| * It is possible that concurrent renames can mess up our list |
| * walk here and result in missing our dentry, resulting in the |
| * false-negative result. d_lookup() protects against concurrent |
| * renames using rename_lock seqlock. |
| * |
| * See Documentation/filesystems/path-lookup.txt for more details. |
| */ |
| rcu_read_lock(); |
| |
| hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
| |
| if (dentry->d_name.hash != hash) |
| continue; |
| |
| spin_lock(&dentry->d_lock); |
| if (dentry->d_parent != parent) |
| goto next; |
| if (d_unhashed(dentry)) |
| goto next; |
| |
| if (!d_same_name(dentry, parent, name)) |
| goto next; |
| |
| dentry->d_lockref.count++; |
| found = dentry; |
| spin_unlock(&dentry->d_lock); |
| break; |
| next: |
| spin_unlock(&dentry->d_lock); |
| } |
| rcu_read_unlock(); |
| |
| return found; |
| } |
| |
| /** |
| * d_hash_and_lookup - hash the qstr then search for a dentry |
| * @dir: Directory to search in |
| * @name: qstr of name we wish to find |
| * |
| * On lookup failure NULL is returned; on bad name - ERR_PTR(-error) |
| */ |
| struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) |
| { |
| /* |
| * Check for a fs-specific hash function. Note that we must |
| * calculate the standard hash first, as the d_op->d_hash() |
| * routine may choose to leave the hash value unchanged. |
| */ |
| name->hash = full_name_hash(dir, name->name, name->len); |
| if (dir->d_flags & DCACHE_OP_HASH) { |
| int err = dir->d_op->d_hash(dir, name); |
| if (unlikely(err < 0)) |
| return ERR_PTR(err); |
| } |
| return d_lookup(dir, name); |
| } |
| EXPORT_SYMBOL(d_hash_and_lookup); |
| |
| /* |
| * When a file is deleted, we have two options: |
| * - turn this dentry into a negative dentry |
| * - unhash this dentry and free it. |
| * |
| * Usually, we want to just turn this into |
| * a negative dentry, but if anybody else is |
| * currently using the dentry or the inode |
| * we can't do that and we fall back on removing |
| * it from the hash queues and waiting for |
| * it to be deleted later when it has no users |
| */ |
| |
| /** |
| * d_delete - delete a dentry |
| * @dentry: The dentry to delete |
| * |
| * Turn the dentry into a negative dentry if possible, otherwise |
| * remove it from the hash queues so it can be deleted later |
| */ |
| |
| void d_delete(struct dentry * dentry) |
| { |
| struct inode *inode = dentry->d_inode; |
| int isdir = d_is_dir(dentry); |
| |
| spin_lock(&inode->i_lock); |
| spin_lock(&dentry->d_lock); |
| /* |
| * Are we the only user? |
| */ |
| if (dentry->d_lockref.count == 1) { |
| dentry->d_flags &= ~DCACHE_CANT_MOUNT; |
| dentry_unlink_inode(dentry); |
| } else { |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| } |
| fsnotify_nameremove(dentry, isdir); |
| } |
| EXPORT_SYMBOL(d_delete); |
| |
| static void __d_rehash(struct dentry *entry) |
| { |
| struct hlist_bl_head *b = d_hash(entry->d_name.hash); |
| |
| hlist_bl_lock(b); |
| hlist_bl_add_head_rcu(&entry->d_hash, b); |
| hlist_bl_unlock(b); |
| } |
| |
| /** |
| * d_rehash - add an entry back to the hash |
| * @entry: dentry to add to the hash |
| * |
| * Adds a dentry to the hash according to its name. |
| */ |
| |
| void d_rehash(struct dentry * entry) |
| { |
| spin_lock(&entry->d_lock); |
| __d_rehash(entry); |
| spin_unlock(&entry->d_lock); |
| } |
| EXPORT_SYMBOL(d_rehash); |
| |
| static inline unsigned start_dir_add(struct inode *dir) |
| { |
| |
| for (;;) { |
| unsigned n = dir->i_dir_seq; |
| if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n) |
| return n; |
| cpu_relax(); |
| } |
| } |
| |
| static inline void end_dir_add(struct inode *dir, unsigned n) |
| { |
| smp_store_release(&dir->i_dir_seq, n + 2); |
| } |
| |
| static void d_wait_lookup(struct dentry *dentry) |
| { |
| if (d_in_lookup(dentry)) { |
| DECLARE_WAITQUEUE(wait, current); |
| add_wait_queue(dentry->d_wait, &wait); |
| do { |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| spin_unlock(&dentry->d_lock); |
| schedule(); |
| spin_lock(&dentry->d_lock); |
| } while (d_in_lookup(dentry)); |
| } |
| } |
| |
| struct dentry *d_alloc_parallel(struct dentry *parent, |
| const struct qstr *name, |
| wait_queue_head_t *wq) |
| { |
| unsigned int hash = name->hash; |
| struct hlist_bl_head *b = in_lookup_hash(parent, hash); |
| struct hlist_bl_node *node; |
| struct dentry *new = d_alloc(parent, name); |
| struct dentry *dentry; |
| unsigned seq, r_seq, d_seq; |
| |
| if (unlikely(!new)) |
| return ERR_PTR(-ENOMEM); |
| |
| retry: |
| rcu_read_lock(); |
| seq = smp_load_acquire(&parent->d_inode->i_dir_seq); |
| r_seq = read_seqbegin(&rename_lock); |
| dentry = __d_lookup_rcu(parent, name, &d_seq); |
| if (unlikely(dentry)) { |
| if (!lockref_get_not_dead(&dentry->d_lockref)) { |
| rcu_read_unlock(); |
| goto retry; |
| } |
| if (read_seqcount_retry(&dentry->d_seq, d_seq)) { |
| rcu_read_unlock(); |
| dput(dentry); |
| goto retry; |
| } |
| rcu_read_unlock(); |
| dput(new); |
| return dentry; |
| } |
| if (unlikely(read_seqretry(&rename_lock, r_seq))) { |
| rcu_read_unlock(); |
| goto retry; |
| } |
| |
| if (unlikely(seq & 1)) { |
| rcu_read_unlock(); |
| goto retry; |
| } |
| |
| hlist_bl_lock(b); |
| if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) { |
| hlist_bl_unlock(b); |
| rcu_read_unlock(); |
| goto retry; |
| } |
| /* |
| * No changes for the parent since the beginning of d_lookup(). |
| * Since all removals from the chain happen with hlist_bl_lock(), |
| * any potential in-lookup matches are going to stay here until |
| * we unlock the chain. All fields are stable in everything |
| * we encounter. |
| */ |
| hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) { |
| if (dentry->d_name.hash != hash) |
| continue; |
| if (dentry->d_parent != parent) |
| continue; |
| if (!d_same_name(dentry, parent, name)) |
| continue; |
| hlist_bl_unlock(b); |
| /* now we can try to grab a reference */ |
| if (!lockref_get_not_dead(&dentry->d_lockref)) { |
| rcu_read_unlock(); |
| goto retry; |
| } |
| |
| rcu_read_unlock(); |
| /* |
| * somebody is likely to be still doing lookup for it; |
| * wait for them to finish |
| */ |
| spin_lock(&dentry->d_lock); |
| d_wait_lookup(dentry); |
| /* |
| * it's not in-lookup anymore; in principle we should repeat |
| * everything from dcache lookup, but it's likely to be what |
| * d_lookup() would've found anyway. If it is, just return it; |
| * otherwise we really have to repeat the whole thing. |
| */ |
| if (unlikely(dentry->d_name.hash != hash)) |
| goto mismatch; |
| if (unlikely(dentry->d_parent != parent)) |
| goto mismatch; |
| if (unlikely(d_unhashed(dentry))) |
| goto mismatch; |
| if (unlikely(!d_same_name(dentry, parent, name))) |
| goto mismatch; |
| /* OK, it *is* a hashed match; return it */ |
| spin_unlock(&dentry->d_lock); |
| dput(new); |
| return dentry; |
| } |
| rcu_read_unlock(); |
| /* we can't take ->d_lock here; it's OK, though. */ |
| new->d_flags |= DCACHE_PAR_LOOKUP; |
| new->d_wait = wq; |
| hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b); |
| hlist_bl_unlock(b); |
| return new; |
| mismatch: |
| spin_unlock(&dentry->d_lock); |
| dput(dentry); |
| goto retry; |
| } |
| EXPORT_SYMBOL(d_alloc_parallel); |
| |
| void __d_lookup_done(struct dentry *dentry) |
| { |
| struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent, |
| dentry->d_name.hash); |
| hlist_bl_lock(b); |
| dentry->d_flags &= ~DCACHE_PAR_LOOKUP; |
| __hlist_bl_del(&dentry->d_u.d_in_lookup_hash); |
| wake_up_all(dentry->d_wait); |
| dentry->d_wait = NULL; |
| hlist_bl_unlock(b); |
| INIT_HLIST_NODE(&dentry->d_u.d_alias); |
| INIT_LIST_HEAD(&dentry->d_lru); |
| } |
| EXPORT_SYMBOL(__d_lookup_done); |
| |
| /* inode->i_lock held if inode is non-NULL */ |
| |
| static inline void __d_add(struct dentry *dentry, struct inode *inode) |
| { |
| struct inode *dir = NULL; |
| unsigned n; |
| spin_lock(&dentry->d_lock); |
| if (unlikely(d_in_lookup(dentry))) { |
| dir = dentry->d_parent->d_inode; |
| n = start_dir_add(dir); |
| __d_lookup_done(dentry); |
| } |
| if (inode) { |
| unsigned add_flags = d_flags_for_inode(inode); |
| hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
| raw_write_seqcount_begin(&dentry->d_seq); |
| __d_set_inode_and_type(dentry, inode, add_flags); |
| raw_write_seqcount_end(&dentry->d_seq); |
| fsnotify_update_flags(dentry); |
| } |
| __d_rehash(dentry); |
| if (dir) |
| end_dir_add(dir, n); |
| spin_unlock(&dentry->d_lock); |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| } |
| |
| /** |
| * d_add - add dentry to hash queues |
| * @entry: dentry to add |
| * @inode: The inode to attach to this dentry |
| * |
| * This adds the entry to the hash queues and initializes @inode. |
| * The entry was actually filled in earlier during d_alloc(). |
| */ |
| |
| void d_add(struct dentry *entry, struct inode *inode) |
| { |
| if (inode) { |
| security_d_instantiate(entry, inode); |
| spin_lock(&inode->i_lock); |
| } |
| __d_add(entry, inode); |
| } |
| EXPORT_SYMBOL(d_add); |
| |
| /** |
| * d_exact_alias - find and hash an exact unhashed alias |
| * @entry: dentry to add |
| * @inode: The inode to go with this dentry |
| * |
| * If an unhashed dentry with the same name/parent and desired |
| * inode already exists, hash and return it. Otherwise, return |
| * NULL. |
| * |
| * Parent directory should be locked. |
| */ |
| struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode) |
| { |
| struct dentry *alias; |
| unsigned int hash = entry->d_name.hash; |
| |
| spin_lock(&inode->i_lock); |
| hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { |
| /* |
| * Don't need alias->d_lock here, because aliases with |
| * d_parent == entry->d_parent are not subject to name or |
| * parent changes, because the parent inode i_mutex is held. |
| */ |
| if (alias->d_name.hash != hash) |
| continue; |
| if (alias->d_parent != entry->d_parent) |
| continue; |
| if (!d_same_name(alias, entry->d_parent, &entry->d_name)) |
| continue; |
| spin_lock(&alias->d_lock); |
| if (!d_unhashed(alias)) { |
| spin_unlock(&alias->d_lock); |
| alias = NULL; |
| } else { |
| __dget_dlock(alias); |
| __d_rehash(alias); |
| spin_unlock(&alias->d_lock); |
| } |
| spin_unlock(&inode->i_lock); |
| return alias; |
| } |
| spin_unlock(&inode->i_lock); |
| return NULL; |
| } |
| EXPORT_SYMBOL(d_exact_alias); |
| |
| /** |
| * dentry_update_name_case - update case insensitive dentry with a new name |
| * @dentry: dentry to be updated |
| * @name: new name |
| * |
| * Update a case insensitive dentry with new case of name. |
| * |
| * dentry must have been returned by d_lookup with name @name. Old and new |
| * name lengths must match (ie. no d_compare which allows mismatched name |
| * lengths). |
| * |
| * Parent inode i_mutex must be held over d_lookup and into this call (to |
| * keep renames and concurrent inserts, and readdir(2) away). |
| */ |
| void dentry_update_name_case(struct dentry *dentry, const struct qstr *name) |
| { |
| BUG_ON(!inode_is_locked(dentry->d_parent->d_inode)); |
| BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ |
| |
| spin_lock(&dentry->d_lock); |
| write_seqcount_begin(&dentry->d_seq); |
| memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); |
| write_seqcount_end(&dentry->d_seq); |
| spin_unlock(&dentry->d_lock); |
| } |
| EXPORT_SYMBOL(dentry_update_name_case); |
| |
| static void swap_names(struct dentry *dentry, struct dentry *target) |
| { |
| if (unlikely(dname_external(target))) { |
| if (unlikely(dname_external(dentry))) { |
| /* |
| * Both external: swap the pointers |
| */ |
| swap(target->d_name.name, dentry->d_name.name); |
| } else { |
| /* |
| * dentry:internal, target:external. Steal target's |
| * storage and make target internal. |
| */ |
| memcpy(target->d_iname, dentry->d_name.name, |
| dentry->d_name.len + 1); |
| dentry->d_name.name = target->d_name.name; |
| target->d_name.name = target->d_iname; |
| } |
| } else { |
| if (unlikely(dname_external(dentry))) { |
| /* |
| * dentry:external, target:internal. Give dentry's |
| * storage to target and make dentry internal |
| */ |
| memcpy(dentry->d_iname, target->d_name.name, |
| target->d_name.len + 1); |
| target->d_name.name = dentry->d_name.name; |
| dentry->d_name.name = dentry->d_iname; |
| } else { |
| /* |
| * Both are internal. |
| */ |
| unsigned int i; |
| BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long))); |
| for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) { |
| swap(((long *) &dentry->d_iname)[i], |
| ((long *) &target->d_iname)[i]); |
| } |
| } |
| } |
| swap(dentry->d_name.hash_len, target->d_name.hash_len); |
| } |
| |
| static void copy_name(struct dentry *dentry, struct dentry *target) |
| { |
| struct external_name *old_name = NULL; |
| if (unlikely(dname_external(dentry))) |
| old_name = external_name(dentry); |
| if (unlikely(dname_external(target))) { |
| atomic_inc(&external_name(target)->u.count); |
| dentry->d_name = target->d_name; |
| } else { |
| memcpy(dentry->d_iname, target->d_name.name, |
| target->d_name.len + 1); |
| dentry->d_name.name = dentry->d_iname; |
| dentry->d_name.hash_len = target->d_name.hash_len; |
| } |
| if (old_name && likely(atomic_dec_and_test(&old_name->u.count))) |
| call_rcu(&old_name->u.head, __d_free_external_name); |
| } |
| |
| /* |
| * __d_move - move a dentry |
| * @dentry: entry to move |
| * @target: new dentry |
| * @exchange: exchange the two dentries |
| * |
| * Update the dcache to reflect the move of a file name. Negative |
| * dcache entries should not be moved in this way. Caller must hold |
| * rename_lock, the i_mutex of the source and target directories, |
| * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). |
| */ |
| static void __d_move(struct dentry *dentry, struct dentry *target, |
| bool exchange) |
| { |
| struct dentry *old_parent, *p; |
| struct inode *dir = NULL; |
| unsigned n; |
| |
| WARN_ON(!dentry->d_inode); |
| if (WARN_ON(dentry == target)) |
| return; |
| |
| BUG_ON(d_ancestor(target, dentry)); |
| old_parent = dentry->d_parent; |
| p = d_ancestor(old_parent, target); |
| if (IS_ROOT(dentry)) { |
| BUG_ON(p); |
| spin_lock(&target->d_parent->d_lock); |
| } else if (!p) { |
| /* target is not a descendent of dentry->d_parent */ |
| spin_lock(&target->d_parent->d_lock); |
| spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED); |
| } else { |
| BUG_ON(p == dentry); |
| spin_lock(&old_parent->d_lock); |
| if (p != target) |
| spin_lock_nested(&target->d_parent->d_lock, |
| DENTRY_D_LOCK_NESTED); |
| } |
| spin_lock_nested(&dentry->d_lock, 2); |
| spin_lock_nested(&target->d_lock, 3); |
| |
| if (unlikely(d_in_lookup(target))) { |
| dir = target->d_parent->d_inode; |
| n = start_dir_add(dir); |
| __d_lookup_done(target); |
| } |
| |
| write_seqcount_begin(&dentry->d_seq); |
| write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED); |
| |
| /* unhash both */ |
| if (!d_unhashed(dentry)) |
| ___d_drop(dentry); |
| if (!d_unhashed(target)) |
| ___d_drop(target); |
| |
| /* ... and switch them in the tree */ |
| dentry->d_parent = target->d_parent; |
| if (!exchange) { |
| copy_name(dentry, target); |
| target->d_hash.pprev = NULL; |
| dentry->d_parent->d_lockref.count++; |
| if (dentry == old_parent) |
| dentry->d_flags |= DCACHE_RCUACCESS; |
| else |
| WARN_ON(!--old_parent->d_lockref.count); |
| } else { |
| target->d_parent = old_parent; |
| swap_names(dentry, target); |
| list_move(&target->d_child, &target->d_parent->d_subdirs); |
| __d_rehash(target); |
| fsnotify_update_flags(target); |
| } |
| list_move(&dentry->d_child, &dentry->d_parent->d_subdirs); |
| __d_rehash(dentry); |
| fsnotify_update_flags(dentry); |
| |
| write_seqcount_end(&target->d_seq); |
| write_seqcount_end(&dentry->d_seq); |
| |
| if (dir) |
| end_dir_add(dir, n); |
| |
| if (dentry->d_parent != old_parent) |
| spin_unlock(&dentry->d_parent->d_lock); |
| if (dentry != old_parent) |
| spin_unlock(&old_parent->d_lock); |
| spin_unlock(&target->d_lock); |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /* |
| * d_move - move a dentry |
| * @dentry: entry to move |
| * @target: new dentry |
| * |
| * Update the dcache to reflect the move of a file name. Negative |
| * dcache entries should not be moved in this way. See the locking |
| * requirements for __d_move. |
| */ |
| void d_move(struct dentry *dentry, struct dentry *target) |
| { |
| write_seqlock(&rename_lock); |
| __d_move(dentry, target, false); |
| write_sequnlock(&rename_lock); |
| } |
| EXPORT_SYMBOL(d_move); |
| |
| /* |
| * d_exchange - exchange two dentries |
| * @dentry1: first dentry |
| * @dentry2: second dentry |
| */ |
| void d_exchange(struct dentry *dentry1, struct dentry *dentry2) |
| { |
| write_seqlock(&rename_lock); |
| |
| WARN_ON(!dentry1->d_inode); |
| WARN_ON(!dentry2->d_inode); |
| WARN_ON(IS_ROOT(dentry1)); |
| WARN_ON(IS_ROOT(dentry2)); |
| |
| __d_move(dentry1, dentry2, true); |
| |
| write_sequnlock(&rename_lock); |
| } |
| |
| /** |
| * d_ancestor - search for an ancestor |
| * @p1: ancestor dentry |
| * @p2: child dentry |
| * |
| * Returns the ancestor dentry of p2 which is a child of p1, if p1 is |
| * an ancestor of p2, else NULL. |
| */ |
| struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) |
| { |
| struct dentry *p; |
| |
| for (p = p2; !IS_ROOT(p); p = p->d_parent) { |
| if (p->d_parent == p1) |
| return p; |
| } |
| return NULL; |
| } |
| |
| /* |
| * This helper attempts to cope with remotely renamed directories |
| * |
| * It assumes that the caller is already holding |
| * dentry->d_parent->d_inode->i_mutex, and rename_lock |
| * |
| * Note: If ever the locking in lock_rename() changes, then please |
| * remember to update this too... |
| */ |
| static int __d_unalias(struct inode *inode, |
| struct dentry *dentry, struct dentry *alias) |
| { |
| struct mutex *m1 = NULL; |
| struct rw_semaphore *m2 = NULL; |
| int ret = -ESTALE; |
| |
| /* If alias and dentry share a parent, then no extra locks required */ |
| if (alias->d_parent == dentry->d_parent) |
| goto out_unalias; |
| |
| /* See lock_rename() */ |
| if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) |
| goto out_err; |
| m1 = &dentry->d_sb->s_vfs_rename_mutex; |
| if (!inode_trylock_shared(alias->d_parent->d_inode)) |
| goto out_err; |
| m2 = &alias->d_parent->d_inode->i_rwsem; |
| out_unalias: |
| __d_move(alias, dentry, false); |
| ret = 0; |
| out_err: |
| if (m2) |
| up_read(m2); |
| if (m1) |
| mutex_unlock(m1); |
| return ret; |
| } |
| |
| /** |
| * d_splice_alias - splice a disconnected dentry into the tree if one exists |
| * @inode: the inode which may have a disconnected dentry |
| * @dentry: a negative dentry which we want to point to the inode. |
| * |
| * If inode is a directory and has an IS_ROOT alias, then d_move that in |
| * place of the given dentry and return it, else simply d_add the inode |
| * to the dentry and return NULL. |
| * |
| * If a non-IS_ROOT directory is found, the filesystem is corrupt, and |
| * we should error out: directories can't have multiple aliases. |
| * |
| * This is needed in the lookup routine of any filesystem that is exportable |
| * (via knfsd) so that we can build dcache paths to directories effectively. |
| * |
| * If a dentry was found and moved, then it is returned. Otherwise NULL |
| * is returned. This matches the expected return value of ->lookup. |
| * |
| * Cluster filesystems may call this function with a negative, hashed dentry. |
| * In that case, we know that the inode will be a regular file, and also this |
| * will only occur during atomic_open. So we need to check for the dentry |
| * being already hashed only in the final case. |
| */ |
| struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) |
| { |
| if (IS_ERR(inode)) |
| return ERR_CAST(inode); |
| |
| BUG_ON(!d_unhashed(dentry)); |
| |
| if (!inode) |
| goto out; |
| |
| security_d_instantiate(dentry, inode); |
| spin_lock(&inode->i_lock); |
| if (S_ISDIR(inode->i_mode)) { |
| struct dentry *new = __d_find_any_alias(inode); |
| if (unlikely(new)) { |
| /* The reference to new ensures it remains an alias */ |
| spin_unlock(&inode->i_lock); |
| write_seqlock(&rename_lock); |
| if (unlikely(d_ancestor(new, dentry))) { |
| write_sequnlock(&rename_lock); |
| dput(new); |
| new = ERR_PTR(-ELOOP); |
| pr_warn_ratelimited( |
| "VFS: Lookup of '%s' in %s %s" |
| " would have caused loop\n", |
| dentry->d_name.name, |
| inode->i_sb->s_type->name, |
| inode->i_sb->s_id); |
| } else if (!IS_ROOT(new)) { |
| struct dentry *old_parent = dget(new->d_parent); |
| int err = __d_unalias(inode, dentry, new); |
| write_sequnlock(&rename_lock); |
| if (err) { |
| dput(new); |
| new = ERR_PTR(err); |
| } |
| dput(old_parent); |
| } else { |
| __d_move(new, dentry, false); |
| write_sequnlock(&rename_lock); |
| } |
| iput(inode); |
| return new; |
| } |
| } |
| out: |
| __d_add(dentry, inode); |
| return NULL; |
| } |
| EXPORT_SYMBOL(d_splice_alias); |
| |
| /* |
| * Test whether new_dentry is a subdirectory of old_dentry. |
| * |
| * Trivially implemented using the dcache structure |
| */ |
| |
| /** |
| * is_subdir - is new dentry a subdirectory of old_dentry |
| * @new_dentry: new dentry |
| * @old_dentry: old dentry |
| * |
| * Returns true if new_dentry is a subdirectory of the parent (at any depth). |
| * Returns false otherwise. |
| * Caller must ensure that "new_dentry" is pinned before calling is_subdir() |
| */ |
| |
| bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) |
| { |
| bool result; |
| unsigned seq; |
| |
| if (new_dentry == old_dentry) |
| return true; |
| |
| do { |
| /* for restarting inner loop in case of seq retry */ |
| seq = read_seqbegin(&rename_lock); |
| /* |
| * Need rcu_readlock to protect against the d_parent trashing |
| * due to d_move |
| */ |
| rcu_read_lock(); |
| if (d_ancestor(old_dentry, new_dentry)) |
| result = true; |
| else |
| result = false; |
| rcu_read_unlock(); |
| } while (read_seqretry(&rename_lock, seq)); |
| |
| return result; |
| } |
| EXPORT_SYMBOL(is_subdir); |
| |
| static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry) |
| { |
| struct dentry *root = data; |
| if (dentry != root) { |
| if (d_unhashed(dentry) || !dentry->d_inode) |
| return D_WALK_SKIP; |
| |
| if (!(dentry->d_flags & DCACHE_GENOCIDE)) { |
| dentry->d_flags |= DCACHE_GENOCIDE; |
| dentry->d_lockref.count--; |
| } |
| } |
| return D_WALK_CONTINUE; |
| } |
| |
| void d_genocide(struct dentry *parent) |
| { |
| d_walk(parent, parent, d_genocide_kill); |
| } |
| |
| EXPORT_SYMBOL(d_genocide); |
| |
| void d_tmpfile(struct dentry *dentry, struct inode *inode) |
| { |
| inode_dec_link_count(inode); |
| BUG_ON(dentry->d_name.name != dentry->d_iname || |
| !hlist_unhashed(&dentry->d_u.d_alias) || |
| !d_unlinked(dentry)); |
| spin_lock(&dentry->d_parent->d_lock); |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| dentry->d_name.len = sprintf(dentry->d_iname, "#%llu", |
| (unsigned long long)inode->i_ino); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&dentry->d_parent->d_lock); |
| d_instantiate(dentry, inode); |
| } |
| EXPORT_SYMBOL(d_tmpfile); |
| |
| static __initdata unsigned long dhash_entries; |
| static int __init set_dhash_entries(char *str) |
| { |
| if (!str) |
| return 0; |
| dhash_entries = simple_strtoul(str, &str, 0); |
| return 1; |
| } |
| __setup("dhash_entries=", set_dhash_entries); |
| |
| static void __init dcache_init_early(void) |
| { |
| /* If hashes are distributed across NUMA nodes, defer |
| * hash allocation until vmalloc space is available. |
| */ |
| if (hashdist) |
| return; |
| |
| dentry_hashtable = |
| alloc_large_system_hash("Dentry cache", |
| sizeof(struct hlist_bl_head), |
| dhash_entries, |
| 13, |
| HASH_EARLY | HASH_ZERO, |
| &d_hash_shift, |
| NULL, |
| 0, |
| 0); |
| d_hash_shift = 32 - d_hash_shift; |
| } |
| |
| static void __init dcache_init(void) |
| { |
| /* |
| * A constructor could be added for stable state like the lists, |
| * but it is probably not worth it because of the cache nature |
| * of the dcache. |
| */ |
| dentry_cache = KMEM_CACHE_USERCOPY(dentry, |
| SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT, |
| d_iname); |
| |
| /* Hash may have been set up in dcache_init_early */ |
| if (!hashdist) |
| return; |
| |
| dentry_hashtable = |
| alloc_large_system_hash("Dentry cache", |
| sizeof(struct hlist_bl_head), |
| dhash_entries, |
| 13, |
| HASH_ZERO, |
| &d_hash_shift, |
| NULL, |
| 0, |
| 0); |
| d_hash_shift = 32 - d_hash_shift; |
| } |
| |
| /* SLAB cache for __getname() consumers */ |
| struct kmem_cache *names_cachep __read_mostly; |
| EXPORT_SYMBOL(names_cachep); |
| |
| void __init vfs_caches_init_early(void) |
| { |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++) |
| INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]); |
| |
| dcache_init_early(); |
| inode_init_early(); |
| } |
| |
| void __init vfs_caches_init(void) |
| { |
| names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0, |
| SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL); |
| |
| dcache_init(); |
| inode_init(); |
| files_init(); |
| files_maxfiles_init(); |
| mnt_init(); |
| bdev_cache_init(); |
| chrdev_init(); |
| } |