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Commit 68db1961 authored by Nikanth Karthikesan's avatar Nikanth Karthikesan Committed by Jens Axboe
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loop: support barrier writes 



Honour barrier requests in the loop back block device driver.
In case of barrier bios, flush the backing file once before processing the
barrier and once after to guarantee ordering. In case of filesystems that
does not support fsync, barrier bios would be failed with -EOPNOTSUPP.

Signed-off-by: default avatarNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 05378940

drivers/block/loop.c

+30 −2
Original line number Diff line number Diff line
@@ -474,10 +474,35 @@ static int do_bio_filebacked(struct loop_device *lo, struct bio *bio) 
	int ret;



	pos = ((loff_t) bio->bi_sector << 9) + lo->lo_offset;

	if (bio_rw(bio) == WRITE)



	if (bio_rw(bio) == WRITE) {

		int barrier = bio_barrier(bio);

		struct file *file = lo->lo_backing_file;



		if (barrier) {

			if (unlikely(!file->f_op->fsync)) {

				ret = -EOPNOTSUPP;

				goto out;

			}



			ret = vfs_fsync(file, file->f_path.dentry, 0);

			if (unlikely(ret)) {

				ret = -EIO;

				goto out;

			}

		}



		ret = lo_send(lo, bio, pos);

	else



		if (barrier && !ret) {

			ret = vfs_fsync(file, file->f_path.dentry, 0);

			if (unlikely(ret))

				ret = -EIO;

		}

	} else

		ret = lo_receive(lo, bio, lo->lo_blocksize, pos);



out:

	return ret;

}
@@ -826,6 +851,9 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, 
	lo->lo_queue->queuedata = lo;

	lo->lo_queue->unplug_fn = loop_unplug;



	if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)

		blk_queue_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN, NULL);



	set_capacity(lo->lo_disk, size);

	bd_set_size(bdev, size << 9);