Commit 554c577c authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Prevent endless loops in gfs2_file_buffered_write 



Currently, instead of performing a short write,
iomap_file_buffered_write will fail when part of its iov iterator cannot
be read.  In contrast, gfs2_file_buffered_write will loop around if it
can read part of the iov iterator, so we can end up in an endless loop.

This should be fixed in iomap_file_buffered_write (and also
generic_perform_write), but this comes a bit late in the 5.16
development cycle, so work around it in the filesystem by
trimming the iov iterator to the known-good size for now.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent a7ac203d

fs/gfs2/file.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -1013,6 +1013,7 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb, 
	struct gfs2_sbd *sdp = GFS2_SB(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);

	struct gfs2_holder *statfs_gh = NULL;

	struct gfs2_holder *statfs_gh = NULL;

	size_t prev_count = 0, window_size = 0;

	size_t prev_count = 0, window_size = 0;

	size_t orig_count = iov_iter_count(from);

	size_t read = 0;

	size_t read = 0;

	ssize_t ret;

	ssize_t ret;
@@ -1057,6 +1058,7 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb, 
	if (inode == sdp->sd_rindex)

	if (inode == sdp->sd_rindex)

		gfs2_glock_dq_uninit(statfs_gh);

		gfs2_glock_dq_uninit(statfs_gh);





	from->count = orig_count - read;

	if (should_fault_in_pages(ret, from, &prev_count, &window_size)) {

	if (should_fault_in_pages(ret, from, &prev_count, &window_size)) {

		size_t leftover;

		size_t leftover;
@@ -1064,6 +1066,7 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb, 
		leftover = fault_in_iov_iter_readable(from, window_size);

		leftover = fault_in_iov_iter_readable(from, window_size);

		gfs2_holder_disallow_demote(gh);

		gfs2_holder_disallow_demote(gh);

		if (leftover != window_size) {

		if (leftover != window_size) {

			from->count = min(from->count, window_size - leftover);

			if (!gfs2_holder_queued(gh)) {

			if (!gfs2_holder_queued(gh)) {

				if (read)

				if (read)

					goto out_uninit;

					goto out_uninit;