[PATCH 6.1 116/195] erofs: fix refcount on the metabuf used for inode lookup

Greg Kroah-Hartman
2024-02-27T14:17:39Z

From: Sandeep Dhavale <dhavale@google.com>

commit 56ee7db31187dc36d501622cb5f1415e88e01c2a upstream.

In erofs_find_target_block() when erofs_dirnamecmp() returns 0,
we do not assign the target metabuf. This causes the caller
erofs_namei()'s erofs_put_metabuf() at the end to be not effective
leaving the refcount on the page.
As the page from metabuf (buf->page) is never put, such page cannot be
migrated or reclaimed. Fix it now by putting the metabuf from
previous loop and assigning the current metabuf to target before
returning so caller erofs_namei() can do the final put as it was
intended.

Fixes: 500edd095648 ("erofs: use meta buffers for inode lookup")
Cc: <stable@vger.kernel.org> # 5.18+
Signed-off-by: Sandeep Dhavale <dhavale@google.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20240221210348.3667795-1-dhavale@google.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/erofs/namei.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

--- a/fs/erofs/namei.c
+++ b/fs/erofs/namei.c
@@ -137,24 +137,24 @@ static void *find_target_block_classic(s
/* string comparison without already matched prefix */
diff = erofs_dirnamecmp(name, &dname, &matched);

- if (!diff) {
- *_ndirents = 0;
- goto out;
- } else if (diff > 0) {
- head = mid + 1;
- startprfx = matched;
-
- if (!IS_ERR(candidate))
- erofs_put_metabuf(target);
- *target = buf;
- candidate = de;
- *_ndirents = ndirents;
- } else {
+ if (diff < 0) {
erofs_put_metabuf(&buf);
-
back = mid - 1;
endprfx = matched;
+ continue;
+ }
+
+ if (!IS_ERR(candidate))
+ erofs_put_metabuf(target);
+ *target = buf;
+ if (!diff) {
+ *_ndirents = 0;
+ return de;
}
+ head = mid + 1;
+ startprfx = matched;
+ candidate = de;
+ *_ndirents = ndirents;
continue;
}
out: /* free if the candidate is valid */