From 68db1961bbf4e16c220ccec4a780e966bc1fece3 Mon Sep 17 00:00:00 2001 From: Nikanth Karthikesan Date: Tue, 24 Mar 2009 12:29:54 +0100 Subject: [PATCH] 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: Nikanth Karthikesan Signed-off-by: Jens Axboe --- drivers/block/loop.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index bf0345577672..9721d100caf1 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -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); -- 2.20.1