[PATCH v2 5/6] smb/client: fix integer truncation in collapse range

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

From: Huiwen He <hehuiwen@kylinos.cn>

smb3_collapse_range() stores the ssize_t return value of
smb2_copychunk_range() in an int. A successful copy larger than
INT_MAX is truncated to a negative value and treated as an error.

Reproducer:

	MNT=/mnt/scratch

	truncate -s 2056M "$MNT/file"
	fallocate --collapse-range -o 1M -l 1M "$MNT/file"

Fix this by using __smb2_copychunk_range(), which reports success as
zero instead of returning the copied byte count.

Before this change, the reproducer fails with:

	fallocate: fallocate failed: Success

and the file size remains unchanged at 2056 MiB. After this change, the
reproducer succeeds and the file size becomes the expected 2055 MiB.

Fixes: 5476b5dd82c8 ("cifs: add support for FALLOC_FL_COLLAPSE_RANGE")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/client/smb2ops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 1a1ff0f33288..ee0f646d1aa2 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -4035,8 +4035,8 @@ static long smb3_collapse_range(struct file *file, struct cifs_tcon *tcon,
 	spin_unlock(&inode->i_lock);
 	netfs_wait_for_outstanding_io(inode);
 
-	rc = smb2_copychunk_range(xid, cfile, cfile, off + len,
-				  old_eof - off - len, off);
+	rc = __smb2_copychunk_range(xid, cfile, cfile, off + len,
+				    old_eof - off - len, off);
 	if (rc < 0)
 		goto out_2;
 
-- 
2.43.0