From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44782C433EF for ; Fri, 22 Jul 2022 07:36:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234427AbiGVHgL (ORCPT ); Fri, 22 Jul 2022 03:36:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234083AbiGVHgJ (ORCPT ); Fri, 22 Jul 2022 03:36:09 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7558A6A9D0; Fri, 22 Jul 2022 00:36:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 36225B8279F; Fri, 22 Jul 2022 07:36:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C531C341C6; Fri, 22 Jul 2022 07:36:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658475364; bh=BrCgpt0Y+dGL8BYfbBvR+y7L5n2fAW8NcR8pieDKD18=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s/NH+cmLNQIwfEFjtjRYn1a5b/fq6FC3ELJVLP5mAZ41Pv84RCVNKXKFHfUQMMUb7 r5hrDbmE5wiwdbyE8Ikp6940ukRBCVHcV5qPcSGWsmfUd/g9MQgP3MXLPPFMkATnUZ ALhh0GKhcScoLYjenTtfVaUmj19j248Q0m71xq6OBL9AvNA+C7adrlQkO5zuSsuu9a HIrBcHjiuQy6Sd3patwXjrqrAU+dy+Zo4A4hsJJlJSwck1ERcFHwJfsk+yfH57tLqx o86yzRcdTYuazw+fEEMiLMtSkIHoDgIEwIgFidSygWrVDda8J/V0KyaRS4Isb2NoGA EpC1Z7Cb2NF7g== Date: Fri, 22 Jul 2022 00:36:01 -0700 From: Eric Biggers To: Keith Busch , Jaegeuk Kim , Chao Yu Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, axboe@kernel.dk, Kernel Team , hch@lst.de, bvanassche@acm.org, damien.lemoal@opensource.wdc.com, pankydev8@gmail.com, Keith Busch , linux-f2fs-devel@lists.sourceforge.net Subject: Re: [PATCHv6 11/11] iomap: add support for dma aligned direct-io Message-ID: References: <20220610195830.3574005-1-kbusch@fb.com> <20220610195830.3574005-12-kbusch@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220610195830.3574005-12-kbusch@fb.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org [+f2fs list and maintainers] On Fri, Jun 10, 2022 at 12:58:30PM -0700, Keith Busch wrote: > From: Keith Busch > > Use the address alignment requirements from the block_device for direct > io instead of requiring addresses be aligned to the block size. > > Signed-off-by: Keith Busch > Reviewed-by: Christoph Hellwig > --- > fs/iomap/direct-io.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 370c3241618a..5d098adba443 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -242,7 +242,6 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, > struct inode *inode = iter->inode; > unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev)); > unsigned int fs_block_size = i_blocksize(inode), pad; > - unsigned int align = iov_iter_alignment(dio->submit.iter); > loff_t length = iomap_length(iter); > loff_t pos = iter->pos; > unsigned int bio_opf; > @@ -253,7 +252,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, > size_t copied = 0; > size_t orig_count; > > - if ((pos | length | align) & ((1 << blkbits) - 1)) > + if ((pos | length) & ((1 << blkbits) - 1) || > + !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter)) > return -EINVAL; > > if (iomap->type == IOMAP_UNWRITTEN) { I noticed that this patch is going to break the following logic in f2fs_should_use_dio() in fs/f2fs/file.c: /* * Direct I/O not aligned to the disk's logical_block_size will be * attempted, but will fail with -EINVAL. * * f2fs additionally requires that direct I/O be aligned to the * filesystem block size, which is often a stricter requirement. * However, f2fs traditionally falls back to buffered I/O on requests * that are logical_block_size-aligned but not fs-block aligned. * * The below logic implements this behavior. */ align = iocb->ki_pos | iov_iter_alignment(iter); if (!IS_ALIGNED(align, i_blocksize(inode)) && IS_ALIGNED(align, bdev_logical_block_size(inode->i_sb->s_bdev))) return false; return true; So, f2fs assumes that __iomap_dio_rw() returns an error if the I/O isn't logical block aligned. This patch changes that. The result is that DIO will sometimes proceed in cases where the I/O doesn't have the fs block alignment required by f2fs for all DIO. Does anyone have any thoughts about what f2fs should be doing here? I think it's weird that f2fs has different behaviors for different degrees of misalignment: fail with EINVAL if not logical block aligned, else fallback to buffered I/O if not fs block aligned. I think it should be one convention or the other. Any opinions about which one it should be? (Note: if you blame the above code, it was written by me. But I was just preserving the existing behavior; I don't know the original motivation.) - Eric