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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CB6D5C433EF for ; Fri, 22 Jul 2022 07:36:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=1MdRSHHqupeDHiescoI428DnT3K+dfJsBGafEauyBbY=; b=gRcrOXoN4/83pKp5MGtbQ6SO/Q bIZLJPPAl9JyNRbw0DzMZ/hrA6k6RbVIIwy4BT5+OS7IqQmuUfSqD8fqadSkEO5osU2LM5b1y8gpb EbO4byM3TaqhzLC1L/L1UJem/9wxt9Fjf1eN1N5a2Fb7BmNetLSISgtvLzfVFGNfvad6JnAfrD7LD f+TXsM678tE3d+CF5JIuZ4p2/0R9wmqSSbUE+ktd3JH2atnzcxX65FQuMGCnRAQ6/yyFQzu3Xm8ky b+LrJ2Qk/ciC36rCwfCVVs9OdCcw4D5YTnnzYylpF9rPydoRyWkBlbl9gec0XvPtAAQLBaDLfmEKq kbEEIn8Q==; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20220610195830.3574005-12-kbusch@fb.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220722_003615_035384_A7F8434C X-CRM114-Status: GOOD ( 26.76 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.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