From: Jan Kara Subject: Re: [PATCH 9/9] blkdev: Fix up AIO+DIO+O_SYNC to do the sync part correctly Date: Tue, 20 Nov 2012 11:15:59 +0100 Message-ID: <20121120101559.GC1408@quack.suse.cz> References: <20121120074116.24645.36369.stgit@blackbox.djwong.org> <20121120075115.25270.62451.stgit@blackbox.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: axboe@kernel.dk, tytso@mit.edu, david@fromorbit.com, jmoyer@redhat.com, bpm@sgi.com, viro@zeniv.linux.org.uk, jack@suse.cz, linux-fsdevel@vger.kernel.org, hch@infradead.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com To: "Darrick J. Wong" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:40701 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751871Ab2KTKQC (ORCPT ); Tue, 20 Nov 2012 05:16:02 -0500 Content-Disposition: inline In-Reply-To: <20121120075115.25270.62451.stgit@blackbox.djwong.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon 19-11-12 23:51:15, Darrick J. Wong wrote: > When performing O_SYNC+AIO+DIO writes to block devices, use the DIO_SYNC_WRITES > flag so that flushes are issued /after/ the write completes, not before. > > Note, however, that for block devices, the DIO setup code ensures that a flush > wq is attached to the superblock of the bdevfs filesystem, not the filesystem > that the device node happens to reside in. This means that unlike regular > files, iocb->ki_filp->f_mapping->host->i_sb != inode->i_sb. Therefore, adjust > Jeff's earlier patch to keep the pointer use consistent and avoid a NULL deref. > > Signed-off-by: Darrick J. Wong > --- > fs/block_dev.c | 5 +++-- > fs/direct-io.c | 3 ++- > 2 files changed, 5 insertions(+), 3 deletions(-) > > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 1a1e5e3..05ff33a 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -235,7 +235,8 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, > struct inode *inode = file->f_mapping->host; > > return __blockdev_direct_IO(rw, iocb, inode, I_BDEV(inode), iov, offset, > - nr_segs, blkdev_get_blocks, NULL, NULL, 0); > + nr_segs, blkdev_get_blocks, NULL, NULL, > + DIO_SYNC_WRITES); > } > > int __sync_blockdev(struct block_device *bdev, int wait) > @@ -1631,7 +1632,7 @@ ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov, > percpu_down_read(&bdev->bd_block_size_semaphore); > > ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); > - if (ret > 0 || ret == -EIOCBQUEUED) { > + if (ret > 0) { > ssize_t err; > > err = generic_write_sync(file, pos, ret); > diff --git a/fs/direct-io.c b/fs/direct-io.c > index b7391d4..c626c43 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -258,7 +258,8 @@ void generic_dio_end_io(struct kiocb *iocb, loff_t offset, ssize_t bytes, > work->ret = ret; > work->offset = offset; > work->len = bytes; > - queue_work(inode->i_sb->s_dio_flush_wq, &work->work); > + queue_work(iocb->ki_filp->f_mapping->host->i_sb->s_dio_flush_wq, > + &work->work); This should be folded into the original patch introducing the s_dio_flush_wq. And please add a comment before this line saying that block devices need a dereference exactly like this... Otherwise the patch looks good so you can add: Reviewed-by: Jan Kara Honza -- Jan Kara SUSE Labs, CR