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fs: fix do_lookup false negative

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fs: fix do_lookup false negative

In do_lookup, if we initially find no dentry, we take the directory i_mutex and
re-check the lookup. If we find a dentry there, then we revalidate it if
needed. However if that revalidate asks for the dentry to be invalidated, we
return -ENOENT from do_lookup. What should happen instead is an attempt to
allocate and lookup a new dentry.

This is probably not noticed because it is rare. It is only reached if a
concurrent create races in first (in which case, the dentry probably won't be
invalidated anyway), or if the racy __d_lookup has failed due to a
false-negative (which is very rare).

Fix this by removing code and have it use the normal reval path.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Nick Piggin 2010-08-18 04:37:30 +10:00 committed by Al Viro
parent 3a48ee8a4a
commit 2e2e88ea8c
1 changed files with 2 additions and 8 deletions
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10
fs/namei.c
View file

@ -709,6 +709,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
dentry = __d_lookup(nd->path.dentry, name);
if (!dentry)
goto need_lookup;
found:
if (dentry->d_op && dentry->d_op->d_revalidate)
goto need_revalidate;
done:
@ -766,14 +767,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
* we waited on the semaphore. Need to revalidate.
*/
mutex_unlock(&dir->i_mutex);
if (dentry->d_op && dentry->d_op->d_revalidate) {
dentry = do_revalidate(dentry, nd);
if (!dentry)
dentry = ERR_PTR(-ENOENT);
}
if (IS_ERR(dentry))
goto fail;
goto done;
goto found;
need_revalidate:
dentry = do_revalidate(dentry, nd);