[PATCH 3/7] smb/client: handle smb2_set_sparse() failure in non-extending fallocate

[Huiwen He <huiwen.he@linux.dev>]

From: Huiwen He <hehuiwen@kylinos.cn>

A non-extending fallocate on a sparse file can return success while the
requested range still contains holes. This affects FALLOC_FL_ALLOCATE_RANGE
within EOF and FALLOC_FL_KEEP_SIZE when CIFS clears the sparse attribute.
Later writes into the range may still fail.

CIFS emulates this operation by clearing the sparse attribute for the
whole file. However, it ignores failure from smb2_set_sparse() and sets
the return value to zero unconditionally.

Return -EOPNOTSUPP when the sparse attribute cannot be cleared. This
prevents CIFS from reporting successful preallocation when the server
rejected FSCTL_SET_SPARSE.

Fixes: f16994797ea8 ("cifs: fix incorrect handling of smb2_set_sparse() return in smb3_simple_falloc")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 554c1f51871d..61b581d86686 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3770,8 +3770,10 @@ static long smb3_simple_falloc(struct file *file, struct cifs_tcon *tcon,
 		}
 	}
 
-	smb2_set_sparse(xid, tcon, cfile, inode, false);
-	rc = 0;
+	if (!smb2_set_sparse(xid, tcon, cfile, inode, false))
+		rc = -EOPNOTSUPP;
+	else
+		rc = 0;
 
 out:
 	if (rc)
-- 
2.43.0