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 78C82309A6F; Wed, 2 Jul 2025 17:51:57 +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=1751478717; cv=none; b=b/HBQf2T9C3WnN0QzSmIjxBbl51IOoTcN+iCWG9JLrmdDecV5jl91EMFTjJjSdFgMRksJDyQHQARovf2KZfSSmQpmvcgFgEq0c6TPXiGchXx6IokU3RoMCL+ayvQhV0l0VImfshAyUBnhkD2MO3dXBRIXkHxDjhdQLvaTp5Jumg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751478717; c=relaxed/simple; bh=AroCB2V0g3NWGJzJs9h05rOXNy9tuygQRV0UcgOoX8U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=utQKlkH0KsD6hKBsWBvFq5LpHOWufKPi71fRSTORh1cAEzBxVNky//e8ZIThKP2EDpKswNYAVtrWUoV8vV4M+XHAWl1H7YjSihhB1H1MjDe0hc3n8rovaQCzmriituaIZhYVbPFIHGqKQOEGam59FgEskv5zYsxAzHBBLp3szRQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ax0VRZrO; 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="Ax0VRZrO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCF18C4CEE7; Wed, 2 Jul 2025 17:51:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751478716; bh=AroCB2V0g3NWGJzJs9h05rOXNy9tuygQRV0UcgOoX8U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ax0VRZrOc4RNV9bVOUKa86DiX5KOreLVa15lL3u/3SIQC8xstkLUbm2cAqb1RWq57 VVBZHjcp82VwQImnbyjnkTGnK5SKv5KhhFA+JBdbqcFQeIAnNlCw8tGSc/oEEYfR/A ErSAmd3glwJzJWIrAwi8KbhfsB9wKCZVCvuo0NsJi7whY/QKTV+kX6c3PpNBW7SXi9 QcP1/pT7/ISq9fAe729Cb1ORVkFib1in1wcM6JSNWahLpeM6sXMu1UFA++rn79fV17 DH6PG5YGTw8h4OxaZk3BdNuWCj/Ug9nWaxewiIDJRy6mk1s4ooA5Lm2MbQvrJ4wnqn INYFQYfsFVmjg== Date: Wed, 2 Jul 2025 10:51:56 -0700 From: "Darrick J. Wong" To: Joanne Koong Cc: linux-fsdevel@vger.kernel.org, hch@lst.de, miklos@szeredi.hu, brauner@kernel.org, anuj20.g@samsung.com, linux-xfs@vger.kernel.org, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, gfs2@lists.linux.dev, kernel-team@meta.com Subject: Re: [PATCH v3 11/16] iomap: add read_folio_range() handler for buffered writes Message-ID: <20250702175156.GE10009@frogsfrogsfrogs> References: <20250624022135.832899-1-joannelkoong@gmail.com> <20250624022135.832899-12-joannelkoong@gmail.com> Precedence: bulk X-Mailing-List: linux-doc@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: <20250624022135.832899-12-joannelkoong@gmail.com> On Mon, Jun 23, 2025 at 07:21:30PM -0700, Joanne Koong wrote: > Add a read_folio_range() handler for buffered writes that filesystems > may pass in if they wish to provide a custom handler for synchronously > reading in the contents of a folio. > > Signed-off-by: Joanne Koong > [hch: renamed to read_folio_range, pass less arguments] > Signed-off-by: Christoph Hellwig > --- > .../filesystems/iomap/operations.rst | 6 +++++ > fs/iomap/buffered-io.c | 25 +++++++++++-------- > include/linux/iomap.h | 10 ++++++++ > 3 files changed, 31 insertions(+), 10 deletions(-) > > diff --git a/Documentation/filesystems/iomap/operations.rst b/Documentation/filesystems/iomap/operations.rst > index 1f5732835567..813e26dbd21e 100644 > --- a/Documentation/filesystems/iomap/operations.rst > +++ b/Documentation/filesystems/iomap/operations.rst > @@ -68,6 +68,8 @@ The following address space operations can be wrapped easily: > void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied, > struct folio *folio); > bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap); > + int (*read_folio_range)(const struct iomap_iter *iter, > + struct folio *folio, loff_t pos, size_t len); > }; > > iomap calls these functions: > @@ -123,6 +125,10 @@ iomap calls these functions: > ``->iomap_valid``, then the iomap should considered stale and the > validation failed. > > + - ``read_folio_range``: Called to synchronously read in the range that will > + be written to. If this function is not provided, iomap will default to > + submitting a bio read request. Excellent! Reviewed-by: "Darrick J. Wong" --D > + > These ``struct kiocb`` flags are significant for buffered I/O with iomap: > > * ``IOCB_NOWAIT``: Turns on ``IOMAP_NOWAIT``. > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index f6e410c9ea7b..897a3ccea2df 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -667,22 +667,23 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len) > pos + len - 1); > } > > -static int iomap_read_folio_sync(loff_t block_start, struct folio *folio, > - size_t poff, size_t plen, const struct iomap *iomap) > +static int iomap_read_folio_range(const struct iomap_iter *iter, > + struct folio *folio, loff_t pos, size_t len) > { > + const struct iomap *srcmap = iomap_iter_srcmap(iter); > struct bio_vec bvec; > struct bio bio; > > - bio_init(&bio, iomap->bdev, &bvec, 1, REQ_OP_READ); > - bio.bi_iter.bi_sector = iomap_sector(iomap, block_start); > - bio_add_folio_nofail(&bio, folio, plen, poff); > + bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ); > + bio.bi_iter.bi_sector = iomap_sector(srcmap, pos); > + bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos)); > return submit_bio_wait(&bio); > } > > -static int __iomap_write_begin(const struct iomap_iter *iter, size_t len, > +static int __iomap_write_begin(const struct iomap_iter *iter, > + const struct iomap_write_ops *write_ops, size_t len, > struct folio *folio) > { > - const struct iomap *srcmap = iomap_iter_srcmap(iter); > struct iomap_folio_state *ifs; > loff_t pos = iter->pos; > loff_t block_size = i_blocksize(iter->inode); > @@ -731,8 +732,12 @@ static int __iomap_write_begin(const struct iomap_iter *iter, size_t len, > if (iter->flags & IOMAP_NOWAIT) > return -EAGAIN; > > - status = iomap_read_folio_sync(block_start, folio, > - poff, plen, srcmap); > + if (write_ops && write_ops->read_folio_range) > + status = write_ops->read_folio_range(iter, > + folio, block_start, plen); > + else > + status = iomap_read_folio_range(iter, > + folio, block_start, plen); > if (status) > return status; > } > @@ -848,7 +853,7 @@ static int iomap_write_begin(struct iomap_iter *iter, > else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) > status = __block_write_begin_int(folio, pos, len, NULL, srcmap); > else > - status = __iomap_write_begin(iter, len, folio); > + status = __iomap_write_begin(iter, write_ops, len, folio); > > if (unlikely(status)) > goto out_unlock; > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 8d20a926b645..5ec651606c51 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -166,6 +166,16 @@ struct iomap_write_ops { > * locked by the iomap code. > */ > bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap); > + > + /* > + * Optional if the filesystem wishes to provide a custom handler for > + * reading in the contents of a folio, otherwise iomap will default to > + * submitting a bio read request. > + * > + * The read must be done synchronously. > + */ > + int (*read_folio_range)(const struct iomap_iter *iter, > + struct folio *folio, loff_t pos, size_t len); > }; > > /* > -- > 2.47.1 > >