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new helper: d_same_name()

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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
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127
fs/dcache.c
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@ -2066,42 +2066,19 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
}
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 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
* 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 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
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 @@ EXPORT_SYMBOL(d_lookup);
*/
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 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
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 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
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 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
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 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
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 @@ EXPORT_SYMBOL(d_add);
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 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
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)) {