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SubjectRe: [PATCH] Block - Honour barrier requests in loop driver
Date
On Wednesday 18 March 2009 10:28:20 Nikanth Karthikesan wrote:
> On Wednesday 18 March 2009 00:39:05 Christoph Hellwig wrote:
> > On Tue, Mar 17, 2009 at 05:39:49PM +0530, Nikanth Karthikesan wrote:
> > > + if (!file->f_op || !file->f_op->fsync) {
> > > + ret = -EOPNOTSUPP;
> > > + goto out;
> > > + }
> >
> > file->f_op is never zero, so you can remove the checks for that.
> > Otherwise looks good.
>
> Thanks for reviewing. I've removed that check.
>
> Jens, Can you merge this?
>
Hi Jens

Did you get to look at this? Can you merge this?

Thanks
Nikanth

>
> 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 <knikanth@suse.de>
>
> ---
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index bf03455..cac7894 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;
> }
>
> @@ -825,6 +850,10 @@ static int loop_set_fd(struct loop_device *lo, fmode_t
> mode, blk_queue_make_request(lo->lo_queue, loop_make_request);
> lo->lo_queue->queuedata = lo;
> lo->lo_queue->unplug_fn = loop_unplug;
> + if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op &&
> + 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);



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