CIFS: use the correct length when pinning memory for direct I/O for write

commit b6bc8a7b993e62f82415a5e3e4a6469e80fea19c upstream.

The current code attempts to pin memory using the largest possible wsize
based on the currect SMB credits. This doesn't cause kernel oops but this
is not optimal as we may pin more pages then actually needed.

Fix this by only pinning what are needed for doing this write I/O.

Signed-off-by: Long Li <longli@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 346735196e8be36bba6ebf7e39067198aa756ccf..c23bf9da93d2bf4891bdaff01137f87a6a73f8b9 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2617,11 +2617,13 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
                if (rc)
                        break;
 
+               cur_len = min_t(const size_t, len, wsize);
+
                if (ctx->direct_io) {
                        ssize_t result;
 
                        result = iov_iter_get_pages_alloc(
-                               from, &pagevec, wsize, &start);
+                               from, &pagevec, cur_len, &start);
                        if (result < 0) {
                                cifs_dbg(VFS,
                                        "direct_writev couldn't get user pages "