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new helper: __lookup_slow() 

lookup_slow() sans locking/unlocking the directory

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-04-06 16:43:47 -04:00
parent 3c95f0dce8
commit 88d8331afb
1 changed files with 18 additions and 9 deletions
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27
fs/namei.c
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@ -1593,22 +1593,21 @@ static int lookup_fast(struct nameidata *nd,
} }
/* Fast lookup failed, do it the slow way */ /* Fast lookup failed, do it the slow way */
static struct dentry *lookup_slow(const struct qstr *name, static struct dentry *__lookup_slow(const struct qstr *name,
struct dentry *dir, struct dentry *dir,
unsigned int flags) unsigned int flags)
{ {
struct dentry *dentry = ERR_PTR(-ENOENT), *old; struct dentry *dentry, *old;
struct inode *inode = dir->d_inode; struct inode *inode = dir->d_inode;
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
inode_lock_shared(inode);
/* Don't go there if it's already dead */ /* Don't go there if it's already dead */
if (unlikely(IS_DEADDIR(inode))) if (unlikely(IS_DEADDIR(inode)))
goto out; return ERR_PTR(-ENOENT);
again: again:
dentry = d_alloc_parallel(dir, name, &wq); dentry = d_alloc_parallel(dir, name, &wq);
if (IS_ERR(dentry)) if (IS_ERR(dentry))
goto out; return dentry;
if (unlikely(!d_in_lookup(dentry))) { if (unlikely(!d_in_lookup(dentry))) {
if (!(flags & LOOKUP_NO_REVAL)) { if (!(flags & LOOKUP_NO_REVAL)) {
int error = d_revalidate(dentry, flags); int error = d_revalidate(dentry, flags);
@ -1630,11 +1629,21 @@ again:
dentry = old; dentry = old;
} }
} }
out:
inode_unlock_shared(inode);
return dentry; return dentry;
} }
static struct dentry *lookup_slow(const struct qstr *name,
struct dentry *dir,
unsigned int flags)
{
struct inode *inode = dir->d_inode;
struct dentry *res;
inode_lock_shared(inode);
res = __lookup_slow(name, dir, flags);
inode_unlock_shared(inode);
return res;
}
static inline int may_lookup(struct nameidata *nd) static inline int may_lookup(struct nameidata *nd)
{ {
if (nd->flags & LOOKUP_RCU) { if (nd->flags & LOOKUP_RCU) {