mm: shmem: avoid unpaired folio_unlock() in shmem_swapin_folio()

Patch series "Some random fixes and cleanup to shmem", v3.

This series contains some simple fixes and cleanup which are made during
learning shmem.  More details can be found in respective patches.

This patch (of 5):

If we get a folio from swap_cache_get_folio() successfully but encounter a
failure before the folio is locked, we will unlock the folio which was not
previously locked.

Put the folio and set it to NULL when a failure occurs before the folio is
locked to fix the issue.

Link: https://lkml.kernel.org/r/20250516170939.965736-1-shikemeng@huaweicloud.com
Link: https://lkml.kernel.org/r/20250516170939.965736-2-shikemeng@huaweicloud.com
Fixes: 058313515d5a ("mm: shmem: fix potential data corruption during shmem swapin")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Kairui Song <kasong@tencent.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 99327c30507c449a3c779a13b77e53582e8c8b61..980fa15f393e753e0b77d1a7b05c8ab801bdd50d 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2335,6 +2335,8 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
                 */
                split_order = shmem_split_large_entry(inode, index, swap, gfp);
                if (split_order < 0) {
+                       folio_put(folio);
+                       folio = NULL;
                        error = split_order;
                        goto failed;
                }