From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3C48433B3; Mon, 27 Oct 2025 16:10:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761581428; cv=none; b=Z91hUnT0kZAYvv7UD2KaLJ0NgaoN91XhKXoIzU2p9wUDJwGqRhkDWxRztXeTz5qkRT/oUO5U2nqxT5EWG/24RCNc0qXxxmpxCs1HtQ+Fn+iQa/qAuDoaE+8HP7ZsBfv7jWg+37A/FblZl3/ImR7kPatx5QIxY0TIMg0SLrKzh6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761581428; c=relaxed/simple; bh=KWyZcSM7YJrEzRFYOxV0414nu6sPOX/btOQt6jFmdC4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ab79jgiVUD2L7ngWiVqv/5Xb8Wkj/vrfqS+9ulTtogIy9nOeJ2VQLwY6fP1KIsfTiN/H9My2WQO0gZyjZ7DveZwfoWAoNCifH7m7bVwlrCI3l4KIjeATxO3cVzIldvEJ+wiRoXBK5JHkgqXTdG8mBHwOhN/tEJHRv5ClBoK8KKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fz3XFv1x; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fz3XFv1x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 384E3C4CEF1; Mon, 27 Oct 2025 16:10:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761581428; bh=KWyZcSM7YJrEzRFYOxV0414nu6sPOX/btOQt6jFmdC4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fz3XFv1xeLDxN9Z+GUBiYC6REQ1R+bLRG+rOBXhw8W1swbwxIVQYDx5re/OjljcA4 AAqu1vGKF5S5d+vmHa3A+aS0vjvmgrBa5leLvp9YNtXsKDpt0sCtONm79hogyse/FQ tVSHO3Lu0wmtWVAxRIoVa0A/NqvVaFTHBp5aerwrtWiKCfnlFWeTrO0kGNlQJ5Rwq/ ZjfVRJgYKG7xZADPntuLvQlAJVMulAw+3VCnkb+lYmjRE1txzYIjCQZrrWyiAeF1XH nRc61CS28D7FCAwkk1e+obVchEUmzQXRShWtfIJhZ0qgRc4mrrbtvdvKadskLcczSi XICgRlx5JEoOw== Date: Mon, 27 Oct 2025 09:10:27 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Christian Brauner , Carlos Maiolino , Qu Wenruo , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Pankaj Raghav Subject: Re: [PATCH 1/4] iomap: add IOMAP_DIO_FSBLOCK_ALIGNED flag Message-ID: <20251027161027.GS3356773@frogsfrogsfrogs> References: <20251023135559.124072-1-hch@lst.de> <20251023135559.124072-2-hch@lst.de> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251023135559.124072-2-hch@lst.de> On Thu, Oct 23, 2025 at 03:55:42PM +0200, Christoph Hellwig wrote: > From: Qu Wenruo > > Btrfs requires all of its bios to be fs block aligned, normally it's > totally fine but with the incoming block size larger than page size > (bs > ps) support, the requirement is no longer met for direct IOs. > > Because iomap_dio_bio_iter() calls bio_iov_iter_get_pages(), only > requiring alignment to be bdev_logical_block_size(). > > In the real world that value is either 512 or 4K, on 4K page sized > systems it means bio_iov_iter_get_pages() can break the bio at any page > boundary, breaking btrfs' requirement for bs > ps cases. > > To address this problem, introduce a new public iomap dio flag, > IOMAP_DIO_FSBLOCK_ALIGNED. > > When calling __iomap_dio_rw() with that new flag, iomap_dio::flags will > inherit that new flag, and iomap_dio_bio_iter() will take fs block size > into the calculation of the alignment, and pass the alignment to > bio_iov_iter_get_pages(), respecting the fs block size requirement. > > The initial user of this flag will be btrfs, which needs to calculate the > checksum for direct read and thus requires the biovec to be fs block > aligned for the incoming bs > ps support. > > Signed-off-by: Qu Wenruo > Reviewed-by: Pankaj Raghav > Signed-off-by: Christoph Hellwig > --- > fs/iomap/direct-io.c | 13 ++++++++++++- > include/linux/iomap.h | 8 ++++++++ > 2 files changed, 20 insertions(+), 1 deletion(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 5d5d63efbd57..ce9cbd2bace0 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -336,10 +336,18 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) > int nr_pages, ret = 0; > u64 copied = 0; > size_t orig_count; > + unsigned int alignment = bdev_logical_block_size(iomap->bdev); > > if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1)) > return -EINVAL; > > + /* > + * Align to the larger one of bdev and fs block size, to meet the > + * alignment requirement of both layers. > + */ > + if (dio->flags & IOMAP_DIO_FSBLOCK_ALIGNED) > + alignment = max(alignment, fs_block_size); > + > if (dio->flags & IOMAP_DIO_WRITE) { > bio_opf |= REQ_OP_WRITE; > > @@ -434,7 +442,7 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) > bio->bi_end_io = iomap_dio_bio_end_io; > > ret = bio_iov_iter_get_pages(bio, dio->submit.iter, > - bdev_logical_block_size(iomap->bdev) - 1); > + alignment - 1); > if (unlikely(ret)) { > /* > * We have to stop part way through an IO. We must fall > @@ -639,6 +647,9 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > if (iocb->ki_flags & IOCB_NOWAIT) > iomi.flags |= IOMAP_NOWAIT; > > + if (dio_flags & IOMAP_DIO_FSBLOCK_ALIGNED) > + dio->flags |= IOMAP_DIO_FSBLOCK_ALIGNED; > + > if (iov_iter_rw(iter) == READ) { > /* reads can always complete inline */ > dio->flags |= IOMAP_DIO_INLINE_COMP; > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 73dceabc21c8..4da13fe24ce8 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -518,6 +518,14 @@ struct iomap_dio_ops { > */ > #define IOMAP_DIO_PARTIAL (1 << 2) > > +/* > + * Ensure each bio is aligned to fs block size. > + * > + * For filesystems which need to calculate/verify the checksum of each fs > + * block. Otherwise they may not be able to handle unaligned bios. > + */ > +#define IOMAP_DIO_FSBLOCK_ALIGNED (1 << 3) A new flag requires an update to IOMAP_F_FLAGS_STRINGS in trace.h for tracepoint decoding. The rest of the changes look ok to me, modulo hch's subsequent fixups. --D > ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > const struct iomap_ops *ops, const struct iomap_dio_ops *dops, > unsigned int dio_flags, void *private, size_t done_before); > -- > 2.47.3 > >