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

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>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index c9bc56b1baac2deac379103f1a4a32da45747b9c..179991435777ed9cae7dad185db5cdd00057bf11 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 "