[PATCH] ocfs2: reject FITRIM ranges shorter than a cluster

ocfs2_trim_mainbm() trims the global bitmap in cluster units, but its
too-short range validation only checks sb->s_blocksize.

On filesystems with a cluster size larger than the block size, a FITRIM
range that is at least one block but shorter than one cluster is
accepted and shifted down to len == 0. The later start + len - 1 and
len -= ... arithmetic then underflows and can drive trimming past the
requested range.

Reject ranges shorter than s_clustersize instead. That preserves the
existing -EINVAL behavior for requests that cannot discard even one
allocation unit and keeps zero-cluster trims out of the group walk.

Fixes: aa89762c5480 ("ocfs2: return EINVAL if the given range to discard is less than block size")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Zhang Cen <[email protected]>
---
 fs/ocfs2/alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 6e5fd3f12a84..be09e766ac1f 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -7576,7 +7576,7 @@ int ocfs2_trim_mainbm(struct super_block *sb, struct fstrim_range *range)
 	len = range->len >> osb->s_clustersize_bits;
 	minlen = range->minlen >> osb->s_clustersize_bits;
 
-	if (minlen >= osb->bitmap_cpg || range->len < sb->s_blocksize)
+	if (minlen >= osb->bitmap_cpg || range->len < osb->s_clustersize)
 		return -EINVAL;
 
 	trace_ocfs2_trim_mainbm(start, len, minlen);
-- 
2.43.0