Re: [bug report] cifs: Fix writeback data corruption

[David Howells <dhowells@redhat.com>]

Dan Carpenter <dan.carpenter@linaro.org> wrote:

> 
> The patch 374ce0748c79: "cifs: Fix writeback data corruption" from
> Feb 22, 2024 (linux-next), leads to the following Smatch static
> checker warning:
> 
> 	fs/smb/client/file.c:2869 cifs_write_back_from_locked_folio()
> 	error: uninitialized symbol 'len'.

Good catch.  len should be the length of the start folio we're given:

--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -2749,7 +2749,7 @@ static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
 	struct cifsFileInfo *cfile = NULL;
 	unsigned long long i_size = i_size_read(inode), max_len;
 	unsigned int xid, wsize;
-	size_t len;
+	size_t len = folio_size(folio);
 	long count = wbc->nr_to_write;
 	int rc;
 
@@ -2793,7 +2793,6 @@ static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
 	 * immediately lockable, is not dirty or is missing, or we reach the
 	 * end of the range.
 	 */
-	len = folio_size(folio);
 	if (start < i_size) {
 		/* Trim the write to the EOF; the extra data is ignored.  Also
 		 * put an upper limit on the size of a single storedata op.

David