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Don't pass inode to ->d_hash() and ->d_compare()

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Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry->d_sb).
A few cases that want more are actually safe with dentry->d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Linus Torvalds
2013-05-21 15:22:44 -07:00
committed by Al Viro
parent 642b704cd7
commit da53be12bb
23 changed files with 108 additions and 165 deletions
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27
fs/dcache.c
View File

@@ -1723,7 +1723,7 @@ 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, length and inode information, so that the
* 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.
@@ -1741,22 +1741,18 @@ enum slow_d_compare {
static noinline enum slow_d_compare slow_dentry_cmp(
const struct dentry *parent,
struct inode *inode,
struct dentry *dentry,
unsigned int seq,
const struct qstr *name)
{
int tlen = dentry->d_name.len;
const char *tname = dentry->d_name.name;
struct inode *i = dentry->d_inode;
if (read_seqcount_retry(&dentry->d_seq, seq)) {
cpu_relax();
return D_COMP_SEQRETRY;
}
if (parent->d_op->d_compare(parent, inode,
dentry, i,
tlen, tname, name))
if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
return D_COMP_NOMATCH;
return D_COMP_OK;
}
@@ -1766,7 +1762,6 @@ static noinline enum slow_d_compare slow_dentry_cmp(
* @parent: parent dentry
* @name: qstr of name we wish to find
* @seqp: returns d_seq value at the point where the dentry was found
* @inode: returns dentry->d_inode when the inode was found valid.
* Returns: dentry, or NULL
*
* __d_lookup_rcu is the dcache lookup function for rcu-walk name
@@ -1793,7 +1788,7 @@ static noinline enum slow_d_compare slow_dentry_cmp(
*/
struct dentry *__d_lookup_rcu(const struct dentry *parent,
const struct qstr *name,
unsigned *seqp, struct inode *inode)
unsigned *seqp)
{
u64 hashlen = name->hash_len;
const unsigned char *str = name->name;
@@ -1827,11 +1822,10 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
seqretry:
/*
* The dentry sequence count protects us from concurrent
* renames, and thus protects inode, parent and name fields.
* renames, and thus protects parent and name fields.
*
* The caller must perform a seqcount check in order
* to do anything useful with the returned dentry,
* including using the 'd_inode' pointer.
* to do anything useful with the returned dentry.
*
* NOTE! We do a "raw" seqcount_begin here. That means that
* we don't wait for the sequence count to stabilize if it
@@ -1845,12 +1839,12 @@ seqretry:
continue;
if (d_unhashed(dentry))
continue;
*seqp = seq;
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
if (dentry->d_name.hash != hashlen_hash(hashlen))
continue;
switch (slow_dentry_cmp(parent, inode, dentry, seq, name)) {
*seqp = seq;
switch (slow_dentry_cmp(parent, dentry, seq, name)) {
case D_COMP_OK:
return dentry;
case D_COMP_NOMATCH:
@@ -1862,6 +1856,7 @@ seqretry:
if (dentry->d_name.hash_len != hashlen)
continue;
*seqp = seq;
if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
return dentry;
}
@@ -1959,9 +1954,7 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
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, parent->d_inode,
dentry, dentry->d_inode,
tlen, tname, name))
if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
goto next;
} else {
if (dentry->d_name.len != len)
@@ -1998,7 +1991,7 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
*/
name->hash = full_name_hash(name->name, name->len);
if (dir->d_flags & DCACHE_OP_HASH) {
int err = dir->d_op->d_hash(dir, dir->d_inode, name);
int err = dir->d_op->d_hash(dir, name);
if (unlikely(err < 0))
return ERR_PTR(err);
}