From e973b1a5999e57da677ab50da5f5479fdc0f0c31 Mon Sep 17 00:00:00 2001 From: "tarangg@amazon.com" Date: Thu, 7 Sep 2017 09:29:23 -0400 Subject: [PATCH] NFS: Sync the correct byte range during synchronous writes Since commit 18290650b1c8 ("NFS: Move buffered I/O locking into nfs_file_write()") nfs_file_write() has not flushed the correct byte range during synchronous writes. generic_write_sync() expects that iocb->ki_pos points to the right edge of the range rather than the left edge. To replicate the problem, open a file with O_DSYNC, have the client write at increasing offsets, and then print the successful offsets. Block port 2049 partway through that sequence, and observe that the client application indicates successful writes in advance of what the server received. Fixes: 18290650b1c8 ("NFS: Move buffered I/O locking into nfs_file_write()") Signed-off-by: Jacob Strauss Signed-off-by: Tarang Gupta Tested-by: Tarang Gupta Cc: stable@vger.kernel.org # v4.8+ Signed-off-by: Trond Myklebust --- fs/nfs/file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/nfs/file.c b/fs/nfs/file.c index 1d71472d239d..a385d1c3f146 100644 --- a/fs/nfs/file.c +++ b/fs/nfs/file.c @@ -631,11 +631,11 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from) if (result <= 0) goto out; - result = generic_write_sync(iocb, result); - if (result < 0) - goto out; written = result; iocb->ki_pos += written; + result = generic_write_sync(iocb, written); + if (result < 0) + goto out; /* Return error values */ if (nfs_need_check_write(file, inode)) { -- 2.20.1