new helper: d_same_name()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
Родитель
ae0a843c74
Коммит
d4c91a8f7e
127
fs/dcache.c
127
fs/dcache.c
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@ -2066,42 +2066,19 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
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}
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EXPORT_SYMBOL(d_add_ci);
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/*
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* Do the slow-case of the dentry name compare.
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*
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* Unlike the dentry_cmp() function, we need to atomically
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* load the name and length information, so that the
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* filesystem can rely on them, and can use the 'name' and
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* 'len' information without worrying about walking off the
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* end of memory etc.
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*
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* Thus the read_seqcount_retry() and the "duplicate" info
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* in arguments (the low-level filesystem should not look
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* at the dentry inode or name contents directly, since
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* rename can change them while we're in RCU mode).
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*/
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enum slow_d_compare {
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D_COMP_OK,
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D_COMP_NOMATCH,
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D_COMP_SEQRETRY,
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};
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static noinline enum slow_d_compare slow_dentry_cmp(
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const struct dentry *parent,
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struct dentry *dentry,
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unsigned int seq,
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const struct qstr *name)
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static inline bool d_same_name(const struct dentry *dentry,
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const struct dentry *parent,
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const struct qstr *name)
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{
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int tlen = dentry->d_name.len;
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const char *tname = dentry->d_name.name;
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if (read_seqcount_retry(&dentry->d_seq, seq)) {
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cpu_relax();
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return D_COMP_SEQRETRY;
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if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
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if (dentry->d_name.len != name->len)
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return false;
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return dentry_cmp(dentry, name->name, name->len) == 0;
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}
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if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
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return D_COMP_NOMATCH;
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return D_COMP_OK;
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return parent->d_op->d_compare(parent, dentry,
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dentry->d_name.len, dentry->d_name.name,
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name) == 0;
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}
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/**
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@ -2180,6 +2157,9 @@ seqretry:
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* dentry compare, we will do seqretries until it is stable,
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* and if we end up with a successful lookup, we actually
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* want to exit RCU lookup anyway.
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*
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* Note that raw_seqcount_begin still *does* smp_rmb(), so
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* we are still guaranteed NUL-termination of ->d_name.name.
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*/
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seq = raw_seqcount_begin(&dentry->d_seq);
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if (dentry->d_parent != parent)
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@ -2188,24 +2168,28 @@ seqretry:
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continue;
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if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
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int tlen;
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const char *tname;
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if (dentry->d_name.hash != hashlen_hash(hashlen))
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continue;
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*seqp = seq;
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switch (slow_dentry_cmp(parent, dentry, seq, name)) {
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case D_COMP_OK:
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return dentry;
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case D_COMP_NOMATCH:
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continue;
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default:
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tlen = dentry->d_name.len;
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tname = dentry->d_name.name;
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/* we want a consistent (name,len) pair */
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if (read_seqcount_retry(&dentry->d_seq, seq)) {
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cpu_relax();
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goto seqretry;
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}
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if (parent->d_op->d_compare(parent, dentry,
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tlen, tname, name) != 0)
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continue;
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} else {
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if (dentry->d_name.hash_len != hashlen)
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continue;
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if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
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continue;
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}
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if (dentry->d_name.hash_len != hashlen)
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continue;
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*seqp = seq;
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if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
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return dentry;
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return dentry;
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}
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return NULL;
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}
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@ -2253,9 +2237,7 @@ EXPORT_SYMBOL(d_lookup);
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*/
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struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
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{
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unsigned int len = name->len;
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unsigned int hash = name->hash;
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const unsigned char *str = name->name;
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struct hlist_bl_head *b = d_hash(parent, hash);
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struct hlist_bl_node *node;
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struct dentry *found = NULL;
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@ -2294,21 +2276,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
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if (d_unhashed(dentry))
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goto next;
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/*
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* It is safe to compare names since d_move() cannot
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* change the qstr (protected by d_lock).
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*/
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if (parent->d_flags & DCACHE_OP_COMPARE) {
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int tlen = dentry->d_name.len;
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const char *tname = dentry->d_name.name;
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if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
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goto next;
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} else {
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if (dentry->d_name.len != len)
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goto next;
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if (dentry_cmp(dentry, str, len))
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goto next;
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}
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if (!d_same_name(dentry, parent, name))
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goto next;
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dentry->d_lockref.count++;
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found = dentry;
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@ -2461,9 +2430,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
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const struct qstr *name,
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wait_queue_head_t *wq)
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{
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unsigned int len = name->len;
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unsigned int hash = name->hash;
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const unsigned char *str = name->name;
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struct hlist_bl_head *b = in_lookup_hash(parent, hash);
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struct hlist_bl_node *node;
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struct dentry *new = d_alloc(parent, name);
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@ -2514,17 +2481,8 @@ retry:
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continue;
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if (dentry->d_parent != parent)
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continue;
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if (parent->d_flags & DCACHE_OP_COMPARE) {
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int tlen = dentry->d_name.len;
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const char *tname = dentry->d_name.name;
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if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
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continue;
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} else {
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if (dentry->d_name.len != len)
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continue;
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if (dentry_cmp(dentry, str, len))
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continue;
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}
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if (!d_same_name(dentry, parent, name))
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continue;
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hlist_bl_unlock(b);
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/* now we can try to grab a reference */
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if (!lockref_get_not_dead(&dentry->d_lockref)) {
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@ -2551,17 +2509,8 @@ retry:
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goto mismatch;
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if (unlikely(d_unhashed(dentry)))
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goto mismatch;
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if (parent->d_flags & DCACHE_OP_COMPARE) {
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int tlen = dentry->d_name.len;
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const char *tname = dentry->d_name.name;
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if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
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goto mismatch;
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} else {
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if (unlikely(dentry->d_name.len != len))
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goto mismatch;
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if (unlikely(dentry_cmp(dentry, str, len)))
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goto mismatch;
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}
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if (unlikely(!d_same_name(dentry, parent, name)))
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goto mismatch;
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/* OK, it *is* a hashed match; return it */
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spin_unlock(&dentry->d_lock);
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dput(new);
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@ -2657,8 +2606,6 @@ EXPORT_SYMBOL(d_add);
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struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
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{
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struct dentry *alias;
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int len = entry->d_name.len;
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const char *name = entry->d_name.name;
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unsigned int hash = entry->d_name.hash;
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spin_lock(&inode->i_lock);
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@ -2672,9 +2619,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
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continue;
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if (alias->d_parent != entry->d_parent)
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continue;
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if (alias->d_name.len != len)
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continue;
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if (dentry_cmp(alias, name, len))
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if (!d_same_name(alias, entry->d_parent, &entry->d_name))
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continue;
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spin_lock(&alias->d_lock);
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if (!d_unhashed(alias)) {
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