Commit e973b1a5 authored Sep 07, 2017 by tarangg@amazon.com Committed by Trond Myklebust Sep 07, 2017

NFS: Sync the correct byte range during synchronous writes



Since commit 18290650 ("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: 18290650 ("NFS: Move buffered I/O locking into nfs_file_write()")
Signed-off-by: Jacob Strauss <jsstraus@amazon.com>
Signed-off-by: Tarang Gupta <tarangg@amazon.com>
Tested-by: Tarang Gupta <tarangg@amazon.com>
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

parent 58a69893

fs/nfs/file.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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)) {

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