[PATCH 2/2] smb/client: mark file sparse before emulating insert range

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

From: Huiwen He <hehuiwen@kylinos.cn>

The SMB client emulates FALLOC_FL_INSERT_RANGE with SET_EOF, COPYCHUNK
and SET_ZERO_DATA.

SET_ZERO_DATA creates a hole only when the file is sparse. On a
non-sparse file, it clears the inserted range but leaves its blocks
allocated, causing the extent count check in xfstests generic/064 to
fail.

Try to mark the file sparse before starting the emulation. As with
existing file extension paths, ignore SET_SPARSE errors and continue
with the existing zero-filled behavior.

Tested with xfstests generic/064 against Samba and ksmbd.

Fixes: 7fe6fe95b936 ("cifs: add FALLOC_FL_INSERT_RANGE support")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index bc7dda6d825a..430b6a1a2d92 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -4006,6 +4006,12 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 
 	count = old_eof - off;
 
+	/*
+	 * SET_ZERO_DATA creates a hole only in a sparse file. Try to mark the file
+	 * sparse, but continue the emulation regardless of the result.
+	 */
+	smb2_set_sparse(xid, tcon, cfile, inode, true);
+
 	filemap_invalidate_lock(inode->i_mapping);
 	rc = filemap_write_and_wait_range(inode->i_mapping, off, new_eof - 1);
 	if (rc < 0)
-- 
2.43.0