vfs: make the dentry cache use the lockref infrastructure
This just replaces the dentry count/lock combination with the lockref
structure that contains both a count and a spinlock, and does the
mechanical conversion to use the lockref infrastructure.
There are no semantic changes here, it's purely syntactic. The
reference lockref implementation uses the spinlock exactly the same way
that the old dcache code did, and the bulk of this patch is just
expanding the internal "d_count" use in the dcache code to use
"d_lockref.count" instead.
This is purely preparation for the real change to make the reference
count updates be lockless during the 3.12 merge window.
[ As with the previous commit, this is a rewritten version of a concept
originally from Waiman, so credit goes to him, blame for any errors
goes to me.
Waiman's patch had some semantic differences for taking advantage of
the lockless update in dget_parent(), while this patch is
intentionally a pure search-and-replace change with no semantic
changes. - Linus ]
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/dcache.c b/fs/dcache.c
index 83cfb83..b949af8 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -229,7 +229,7 @@
*/
static void d_free(struct dentry *dentry)
{
- BUG_ON(dentry->d_count);
+ BUG_ON(dentry->d_lockref.count);
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
@@ -467,7 +467,7 @@
}
if (ref)
- dentry->d_count--;
+ dentry->d_lockref.count--;
/*
* inform the fs via d_prune that this dentry is about to be
* unhashed and destroyed.
@@ -513,15 +513,10 @@
return;
repeat:
- if (dentry->d_count == 1)
+ if (dentry->d_lockref.count == 1)
might_sleep();
- spin_lock(&dentry->d_lock);
- BUG_ON(!dentry->d_count);
- if (dentry->d_count > 1) {
- dentry->d_count--;
- spin_unlock(&dentry->d_lock);
+ if (lockref_put_or_lock(&dentry->d_lockref))
return;
- }
if (dentry->d_flags & DCACHE_OP_DELETE) {
if (dentry->d_op->d_delete(dentry))
@@ -535,7 +530,7 @@
dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
- dentry->d_count--;
+ dentry->d_lockref.count--;
spin_unlock(&dentry->d_lock);
return;
@@ -590,7 +585,7 @@
* We also need to leave mountpoints alone,
* directory or not.
*/
- if (dentry->d_count > 1 && dentry->d_inode) {
+ if (dentry->d_lockref.count > 1 && dentry->d_inode) {
if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
spin_unlock(&dentry->d_lock);
return -EBUSY;
@@ -606,14 +601,12 @@
/* This must be called with d_lock held */
static inline void __dget_dlock(struct dentry *dentry)
{
- dentry->d_count++;
+ dentry->d_lockref.count++;
}
static inline void __dget(struct dentry *dentry)
{
- spin_lock(&dentry->d_lock);
- __dget_dlock(dentry);
- spin_unlock(&dentry->d_lock);
+ lockref_get(&dentry->d_lockref);
}
struct dentry *dget_parent(struct dentry *dentry)
@@ -634,8 +627,8 @@
goto repeat;
}
rcu_read_unlock();
- BUG_ON(!ret->d_count);
- ret->d_count++;
+ BUG_ON(!ret->d_lockref.count);
+ ret->d_lockref.count++;
spin_unlock(&ret->d_lock);
return ret;
}
@@ -718,7 +711,7 @@
spin_lock(&inode->i_lock);
hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
- if (!dentry->d_count) {
+ if (!dentry->d_lockref.count) {
__dget_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
@@ -763,12 +756,8 @@
/* Prune ancestors. */
dentry = parent;
while (dentry) {
- spin_lock(&dentry->d_lock);
- if (dentry->d_count > 1) {
- dentry->d_count--;
- spin_unlock(&dentry->d_lock);
+ if (lockref_put_or_lock(&dentry->d_lockref))
return;
- }
dentry = dentry_kill(dentry, 1);
}
}
@@ -793,7 +782,7 @@
* the LRU because of laziness during lookup. Do not free
* it - just keep it off the LRU list.
*/
- if (dentry->d_count) {
+ if (dentry->d_lockref.count) {
dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock);
continue;
@@ -913,7 +902,7 @@
dentry_lru_del(dentry);
__d_shrink(dentry);
- if (dentry->d_count != 0) {
+ if (dentry->d_lockref.count != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
" still in use (%d)"
@@ -922,7 +911,7 @@
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry->d_name.name,
- dentry->d_count,
+ dentry->d_lockref.count,
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
BUG();
@@ -933,7 +922,7 @@
list_del(&dentry->d_u.d_child);
} else {
parent = dentry->d_parent;
- parent->d_count--;
+ parent->d_lockref.count--;
list_del(&dentry->d_u.d_child);
}
@@ -981,7 +970,7 @@
dentry = sb->s_root;
sb->s_root = NULL;
- dentry->d_count--;
+ dentry->d_lockref.count--;
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_bl_empty(&sb->s_anon)) {
@@ -1147,7 +1136,7 @@
* loop in shrink_dcache_parent() might not make any progress
* and loop forever.
*/
- if (dentry->d_count) {
+ if (dentry->d_lockref.count) {
dentry_lru_del(dentry);
} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
dentry_lru_move_list(dentry, dispose);
@@ -1269,7 +1258,7 @@
smp_wmb();
dentry->d_name.name = dname;
- dentry->d_count = 1;
+ dentry->d_lockref.count = 1;
dentry->d_flags = 0;
spin_lock_init(&dentry->d_lock);
seqcount_init(&dentry->d_seq);
@@ -1970,7 +1959,7 @@
goto next;
}
- dentry->d_count++;
+ dentry->d_lockref.count++;
found = dentry;
spin_unlock(&dentry->d_lock);
break;
@@ -2069,7 +2058,7 @@
spin_lock(&dentry->d_lock);
inode = dentry->d_inode;
isdir = S_ISDIR(inode->i_mode);
- if (dentry->d_count == 1) {
+ if (dentry->d_lockref.count == 1) {
if (!spin_trylock(&inode->i_lock)) {
spin_unlock(&dentry->d_lock);
cpu_relax();
@@ -2948,7 +2937,7 @@
}
if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
dentry->d_flags |= DCACHE_GENOCIDE;
- dentry->d_count--;
+ dentry->d_lockref.count--;
}
spin_unlock(&dentry->d_lock);
}
@@ -2956,7 +2945,7 @@
struct dentry *child = this_parent;
if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
this_parent->d_flags |= DCACHE_GENOCIDE;
- this_parent->d_count--;
+ this_parent->d_lockref.count--;
}
this_parent = try_to_ascend(this_parent, locked, seq);
if (!this_parent)
diff --git a/fs/namei.c b/fs/namei.c
index 8b61d10..7720fbd 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -536,8 +536,8 @@
* a reference at this point.
*/
BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
- BUG_ON(!parent->d_count);
- parent->d_count++;
+ BUG_ON(!parent->d_lockref.count);
+ parent->d_lockref.count++;
spin_unlock(&dentry->d_lock);
}
spin_unlock(&parent->d_lock);
@@ -3327,7 +3327,7 @@
{
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
- if (dentry->d_count == 1)
+ if (dentry->d_lockref.count == 1)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 4a12532..efdc944 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -9,6 +9,7 @@
#include <linux/seqlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
+#include <linux/lockref.h>
struct nameidata;
struct path;
@@ -100,6 +101,8 @@
# endif
#endif
+#define d_lock d_lockref.lock
+
struct dentry {
/* RCU lookup touched fields */
unsigned int d_flags; /* protected by d_lock */
@@ -112,8 +115,7 @@
unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
/* Ref lookup also touches following */
- unsigned int d_count; /* protected by d_lock */
- spinlock_t d_lock; /* per dentry lock */
+ struct lockref d_lockref; /* per-dentry lock and refcount */
const struct dentry_operations *d_op;
struct super_block *d_sb; /* The root of the dentry tree */
unsigned long d_time; /* used by d_revalidate */
@@ -318,7 +320,7 @@
assert_spin_locked(&dentry->d_lock);
if (!read_seqcount_retry(&dentry->d_seq, seq)) {
ret = 1;
- dentry->d_count++;
+ dentry->d_lockref.count++;
}
return ret;
@@ -326,7 +328,7 @@
static inline unsigned d_count(const struct dentry *dentry)
{
- return dentry->d_count;
+ return dentry->d_lockref.count;
}
/* validate "insecure" dentry pointer */
@@ -357,17 +359,14 @@
static inline struct dentry *dget_dlock(struct dentry *dentry)
{
if (dentry)
- dentry->d_count++;
+ dentry->d_lockref.count++;
return dentry;
}
static inline struct dentry *dget(struct dentry *dentry)
{
- if (dentry) {
- spin_lock(&dentry->d_lock);
- dget_dlock(dentry);
- spin_unlock(&dentry->d_lock);
- }
+ if (dentry)
+ lockref_get(&dentry->d_lockref);
return dentry;
}