new helper: d_same_name()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index dc37c02..040c258 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2066,42 +2066,19 @@
}
EXPORT_SYMBOL(d_add_ci);
-/*
- * Do the slow-case of the dentry name compare.
- *
- * Unlike the dentry_cmp() function, we need to atomically
- * load the name and length information, so that the
- * filesystem can rely on them, and can use the 'name' and
- * 'len' information without worrying about walking off the
- * end of memory etc.
- *
- * Thus the read_seqcount_retry() and the "duplicate" info
- * in arguments (the low-level filesystem should not look
- * at the dentry inode or name contents directly, since
- * rename can change them while we're in RCU mode).
- */
-enum slow_d_compare {
- D_COMP_OK,
- D_COMP_NOMATCH,
- D_COMP_SEQRETRY,
-};
-static noinline enum slow_d_compare slow_dentry_cmp(
- const struct dentry *parent,
- struct dentry *dentry,
- unsigned int seq,
- const struct qstr *name)
+static inline bool d_same_name(const struct dentry *dentry,
+ const struct dentry *parent,
+ const struct qstr *name)
{
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
-
- if (read_seqcount_retry(&dentry->d_seq, seq)) {
- cpu_relax();
- return D_COMP_SEQRETRY;
+ 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;
}
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- return D_COMP_NOMATCH;
- return D_COMP_OK;
+ return parent->d_op->d_compare(parent, dentry,
+ dentry->d_name.len, dentry->d_name.name,
+ name) == 0;
}
/**
@@ -2180,6 +2157,9 @@
* 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)
@@ -2188,24 +2168,28 @@
continue;
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
+ int tlen;
+ const char *tname;
if (dentry->d_name.hash != hashlen_hash(hashlen))
continue;
- *seqp = seq;
- switch (slow_dentry_cmp(parent, dentry, seq, name)) {
- case D_COMP_OK:
- return dentry;
- case D_COMP_NOMATCH:
- continue;
- default:
+ 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(parent, 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;
}
-
- if (dentry->d_name.hash_len != hashlen)
- continue;
*seqp = seq;
- if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
- return dentry;
+ return dentry;
}
return NULL;
}
@@ -2253,9 +2237,7 @@
*/
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
{
- unsigned int len = name->len;
unsigned int hash = name->hash;
- const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *found = NULL;
@@ -2294,21 +2276,8 @@
if (d_unhashed(dentry))
goto next;
- /*
- * It is safe to compare names since d_move() cannot
- * change the qstr (protected by d_lock).
- */
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- goto next;
- } else {
- if (dentry->d_name.len != len)
- goto next;
- if (dentry_cmp(dentry, str, len))
- goto next;
- }
+ if (!d_same_name(dentry, parent, name))
+ goto next;
dentry->d_lockref.count++;
found = dentry;
@@ -2461,9 +2430,7 @@
const struct qstr *name,
wait_queue_head_t *wq)
{
- unsigned int len = name->len;
unsigned int hash = name->hash;
- const unsigned char *str = name->name;
struct hlist_bl_head *b = in_lookup_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *new = d_alloc(parent, name);
@@ -2514,17 +2481,8 @@
continue;
if (dentry->d_parent != parent)
continue;
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- continue;
- } else {
- if (dentry->d_name.len != len)
- continue;
- if (dentry_cmp(dentry, str, len))
- 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)) {
@@ -2551,17 +2509,8 @@
goto mismatch;
if (unlikely(d_unhashed(dentry)))
goto mismatch;
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- goto mismatch;
- } else {
- if (unlikely(dentry->d_name.len != len))
- goto mismatch;
- if (unlikely(dentry_cmp(dentry, str, len)))
- 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);
@@ -2657,8 +2606,6 @@
struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
{
struct dentry *alias;
- int len = entry->d_name.len;
- const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash;
spin_lock(&inode->i_lock);
@@ -2672,9 +2619,7 @@
continue;
if (alias->d_parent != entry->d_parent)
continue;
- if (alias->d_name.len != len)
- continue;
- if (dentry_cmp(alias, name, len))
+ if (!d_same_name(alias, entry->d_parent, &entry->d_name))
continue;
spin_lock(&alias->d_lock);
if (!d_unhashed(alias)) {