[PATCH] ext4: Fix dcache lookup of !casefolded directories

[PATCH] ext4: Fix dcache lookup of !casefolded directories

[Gabriel Krisman Bertazi]

Found by visual inspection, this wasn't caught by my xfstest, since it's
effect is ignoring positive dentries in the cache the fallback just goes
to the disk.  it was introduced in the last iteration of the
case-insensitive patch.

d_compare should return 0 when the entries match, so make sure we are
correctly comparing the entire string if the encoding feature is set and
we are on a case-INsensitive directory.

Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups")
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 fs/ext4/dir.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 884a6e776809..c7843b149a1e 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -671,7 +671,7 @@ static int ext4_d_compare(const struct dentry *dentry, unsigned int len,
 	if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) {
 		if (len != name->len)
 			return -1;
-		return !memcmp(str, name, len);
+		return memcmp(str, name->name, len);
 	}
 
 	return ext4_ci_compare(dentry->d_parent->d_inode, name, &qstr);
-- 
2.20.1

Re: [PATCH] ext4: Fix dcache lookup of !casefolded directories

[Theodore Ts'o]

On Fri, May 24, 2019 at 06:41:29PM -0400, Gabriel Krisman Bertazi wrote:
> Found by visual inspection, this wasn't caught by my xfstest, since it's
> effect is ignoring positive dentries in the cache the fallback just goes
> to the disk.  it was introduced in the last iteration of the
> case-insensitive patch.
> 
> d_compare should return 0 when the entries match, so make sure we are
> correctly comparing the entire string if the encoding feature is set and
> we are on a case-INsensitive directory.
> 
> Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups")
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

Applied, thanks.

I'll note that half the implementations of *_d_compare seem to use
!!memcmp(), and half use memcmp().

The callers of d_compare only seems to care if it's 0 or != 0, so I
guess it doesn't matter...

				- Ted