openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

new helper: d_same_name() 

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-06-25 23:33:49 -04:00
parent ae0a843c74
commit d4c91a8f7e
1 changed files with 36 additions and 91 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

127
fs/dcache.c
View File

@ -2066,42 +2066,19 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
} }
EXPORT_SYMBOL(d_add_ci); 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( static inline bool d_same_name(const struct dentry *dentry,
const struct dentry *parent, const struct dentry *parent,
struct dentry *dentry, const struct qstr *name)
unsigned int seq,
const struct qstr *name)
{ {
int tlen = dentry->d_name.len; if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
const char *tname = dentry->d_name.name; if (dentry->d_name.len != name->len)
return false;
if (read_seqcount_retry(&dentry->d_seq, seq)) { return dentry_cmp(dentry, name->name, name->len) == 0;
cpu_relax();
return D_COMP_SEQRETRY;
} }
if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) return parent->d_op->d_compare(parent, dentry,
return D_COMP_NOMATCH; dentry->d_name.len, dentry->d_name.name,
return D_COMP_OK; name) == 0;
} }
/** /**
@ -2180,6 +2157,9 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
* dentry compare, we will do seqretries until it is stable, * dentry compare, we will do seqretries until it is stable,
* and if we end up with a successful lookup, we actually * and if we end up with a successful lookup, we actually
* want to exit RCU lookup anyway. * 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); seq = raw_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent) if (dentry->d_parent != parent)
@ -2188,24 +2168,28 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
continue; continue;
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
int tlen;
const char *tname;
if (dentry->d_name.hash != hashlen_hash(hashlen)) if (dentry->d_name.hash != hashlen_hash(hashlen))
continue; continue;
*seqp = seq; tlen = dentry->d_name.len;
switch (slow_dentry_cmp(parent, dentry, seq, name)) { tname = dentry->d_name.name;
case D_COMP_OK: /* we want a consistent (name,len) pair */
return dentry; if (read_seqcount_retry(&dentry->d_seq, seq)) {
case D_COMP_NOMATCH: cpu_relax();
continue;
default:
goto seqretry; 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; *seqp = seq;
if (!dentry_cmp(dentry, str, hashlen_len(hashlen))) return dentry;
return dentry;
} }
return NULL; return NULL;
} }
@ -2253,9 +2237,7 @@ EXPORT_SYMBOL(d_lookup);
*/ */
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
{ {
unsigned int len = name->len;
unsigned int hash = name->hash; unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(parent, hash); struct hlist_bl_head *b = d_hash(parent, hash);
struct hlist_bl_node *node; struct hlist_bl_node *node;
struct dentry *found = NULL; struct dentry *found = NULL;
@ -2294,21 +2276,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
if (d_unhashed(dentry)) if (d_unhashed(dentry))
goto next; goto next;
/* if (!d_same_name(dentry, parent, name))
* It is safe to compare names since d_move() cannot goto next;
* 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;
}
dentry->d_lockref.count++; dentry->d_lockref.count++;
found = dentry; found = dentry;
@ -2461,9 +2430,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
const struct qstr *name, const struct qstr *name,
wait_queue_head_t *wq) wait_queue_head_t *wq)
{ {
unsigned int len = name->len;
unsigned int hash = name->hash; unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct hlist_bl_head *b = in_lookup_hash(parent, hash); struct hlist_bl_head *b = in_lookup_hash(parent, hash);
struct hlist_bl_node *node; struct hlist_bl_node *node;
struct dentry *new = d_alloc(parent, name); struct dentry *new = d_alloc(parent, name);
@ -2514,17 +2481,8 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
continue; continue;
if (dentry->d_parent != parent) if (dentry->d_parent != parent)
continue; continue;
if (parent->d_flags & DCACHE_OP_COMPARE) { if (!d_same_name(dentry, parent, name))
int tlen = dentry->d_name.len; continue;
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;
}
hlist_bl_unlock(b); hlist_bl_unlock(b);
/* now we can try to grab a reference */ /* now we can try to grab a reference */
if (!lockref_get_not_dead(&dentry->d_lockref)) { if (!lockref_get_not_dead(&dentry->d_lockref)) {
@ -2551,17 +2509,8 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
goto mismatch; goto mismatch;
if (unlikely(d_unhashed(dentry))) if (unlikely(d_unhashed(dentry)))
goto mismatch; goto mismatch;
if (parent->d_flags & DCACHE_OP_COMPARE) { if (unlikely(!d_same_name(dentry, parent, name)))
int tlen = dentry->d_name.len; goto mismatch;
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;
}
/* OK, it *is* a hashed match; return it */ /* OK, it *is* a hashed match; return it */
spin_unlock(&dentry->d_lock); spin_unlock(&dentry->d_lock);
dput(new); dput(new);
@ -2657,8 +2606,6 @@ EXPORT_SYMBOL(d_add);
struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode) struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
{ {
struct dentry *alias; struct dentry *alias;
int len = entry->d_name.len;
const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash; unsigned int hash = entry->d_name.hash;
spin_lock(&inode->i_lock); spin_lock(&inode->i_lock);
@ -2672,9 +2619,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
continue; continue;
if (alias->d_parent != entry->d_parent) if (alias->d_parent != entry->d_parent)
continue; continue;
if (alias->d_name.len != len) if (!d_same_name(alias, entry->d_parent, &entry->d_name))
continue;
if (dentry_cmp(alias, name, len))
continue; continue;
spin_lock(&alias->d_lock); spin_lock(&alias->d_lock);
if (!d_unhashed(alias)) { if (!d_unhashed(alias)) {