From: Jeff Moyer Subject: Re: [PATCH 9/9] blkdev: Fix up AIO+DIO+O_SYNC to do the sync part correctly Date: Tue, 20 Nov 2012 15:47:54 -0500 Message-ID: References: <20121120074116.24645.36369.stgit@blackbox.djwong.org> <20121120075115.25270.62451.stgit@blackbox.djwong.org> <20121120101559.GC1408@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Darrick J. Wong" , axboe@kernel.dk, tytso@mit.edu, david@fromorbit.com, bpm@sgi.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, hch@infradead.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com To: Jan Kara Return-path: Received: from mx1.redhat.com ([209.132.183.28]:65456 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752464Ab2KTUsI (ORCPT ); Tue, 20 Nov 2012 15:48:08 -0500 In-Reply-To: <20121120101559.GC1408@quack.suse.cz> (Jan Kara's message of "Tue, 20 Nov 2012 11:15:59 +0100") Sender: linux-ext4-owner@vger.kernel.org List-ID: Jan Kara writes: > 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 When you say, "This," do you mean that one change, or the whole patch? Cheers, Jeff