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 8B17527B331; Fri, 31 Oct 2025 15:24:07 +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=1761924248; cv=none; b=CHg20VGybE23da+/6Bw84KUPlChWPgt2cOosfI7AMC7x5cBgmFxMeQdD9/LERN8Nsg7jl6G+/yhYMZn326xs2MQqA8teJBeFIZgnntpf0ORjRIT7MeYtSHvRNrjutxq5e57QiLCRzkuDxDW2kw0yYQwPlrcyfE8xuVwiCB6gZHg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761924248; c=relaxed/simple; bh=o8OYUkrvrAalen5EIlWZ1kI7gpobmbgMMZ6EzFvJDRU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kciZhT9qj7zQBtSmTfC6hbdFsYQybaDrHkZDMbLP4ki0JT5XJWAF8dBX0w0ROj/E6pE8htqhS6HNXMxPJEKEB8rtG1dTHvGkuchi8FffDDER0fPtc26xZRGsen/j08guo0PlLxJLMTkEgGoMqrBY9LKM55R/I8NcpD5AabnowgM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ffMRckRH; 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="ffMRckRH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DABD2C4CEE7; Fri, 31 Oct 2025 15:24:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761924246; bh=o8OYUkrvrAalen5EIlWZ1kI7gpobmbgMMZ6EzFvJDRU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ffMRckRHHzSd6Mz9AKNUK4KDfJbYa60u8pLWMTZYzkBeQfmkN4XXxysEo0AZGnFJt DW7rNj/sW7lzf7cwEqJqggpVbLdU12LKD4uOinI9eMuxseQopN2qMD0XnEWeOOZkkQ WNolDOXMhT+2cxzImiA9ISqQpVKTWCAsbzaonPs8TYCz27S2jp/KBpR+mgCEeySyrN AOFUdNAMZmFf3X01V1gxE0p05fTdNktvU7ihJFyjRL98Q0GR3Hly3wzlPVPvZl3iMS yzyxgd5v2kAKqzEkapt9xGlqTIv4D04qh1hKdsN3hhNunkUe9I1ZYx1f2O5R5phrT+ YjGpfvDryjNig== Date: Fri, 31 Oct 2025 08:24:06 -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 1/2] iomap: add IOMAP_DIO_FSBLOCK_ALIGNED flag Message-ID: <20251031152406.GO6174@frogsfrogsfrogs> References: <20251031131045.1613229-1-hch@lst.de> <20251031131045.1613229-2-hch@lst.de> Precedence: bulk X-Mailing-List: linux-xfs@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: <20251031131045.1613229-2-hch@lst.de> On Fri, Oct 31, 2025 at 02:10:26PM +0100, 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 > [hch: also align pos/len, incorporate the trace flags from Darrick] > Signed-off-by: Christoph Hellwig LGTM Reviewed-by: "Darrick J. Wong" --D > --- > fs/iomap/direct-io.c | 17 +++++++++++++++-- > fs/iomap/trace.h | 7 ++++--- > include/linux/iomap.h | 8 ++++++++ > 3 files changed, 27 insertions(+), 5 deletions(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 5d5d63efbd57..13def8418659 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -336,8 +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; > > - if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1)) > + /* > + * File systems that write out of place and always allocate new blocks > + * need each bio to be block aligned as that's the unit of allocation. > + */ > + if (dio->flags & IOMAP_DIO_FSBLOCK_ALIGNED) > + alignment = fs_block_size; > + else > + alignment = bdev_logical_block_size(iomap->bdev); > + > + if ((pos | length) & (alignment - 1)) > return -EINVAL; > > if (dio->flags & IOMAP_DIO_WRITE) { > @@ -434,7 +444,7 @@ 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 +649,9 @@ __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/fs/iomap/trace.h b/fs/iomap/trace.h > index a61c1dae4742..532787277b16 100644 > --- a/fs/iomap/trace.h > +++ b/fs/iomap/trace.h > @@ -122,9 +122,10 @@ DEFINE_RANGE_EVENT(iomap_zero_iter); > > > #define IOMAP_DIO_STRINGS \ > - {IOMAP_DIO_FORCE_WAIT, "DIO_FORCE_WAIT" }, \ > - {IOMAP_DIO_OVERWRITE_ONLY, "DIO_OVERWRITE_ONLY" }, \ > - {IOMAP_DIO_PARTIAL, "DIO_PARTIAL" } > + {IOMAP_DIO_FORCE_WAIT, "DIO_FORCE_WAIT" }, \ > + {IOMAP_DIO_OVERWRITE_ONLY, "DIO_OVERWRITE_ONLY" }, \ > + {IOMAP_DIO_PARTIAL, "DIO_PARTIAL" }, \ > + {IOMAP_DIO_FSBLOCK_ALIGNED, "DIO_FSBLOCK_ALIGNED" } > > DECLARE_EVENT_CLASS(iomap_class, > TP_PROTO(struct inode *inode, struct iomap *iomap), > 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) > + > 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 > >