don't build bios/contexts over multiple iomaps v3

don't build bios/contexts over multiple iomaps v3

[Christoph Hellwig]

Hi all,

this patch changes how iomap submits bios for reads.  The old behavior
to build up bios across iomap was already considered problematic for
a while, but we now ran into a erofs bug because of it, so it's time
to finally fix it.

It would be great to get the fix into 7.2 as the fixed bug can be
triggered by users.

Changes since v2:
 - drop an unused argument
 - make sure we submit for the same iteration to not leave a landmine
   for future changes

Changes since v1:
 - don't submit fuse context after each iteration
 - consolidate some code to support the above
 - fix a bug in the fs PI support found while doing the above

[PATCH 1/3] iomap: consolidate bio submission

[Christoph Hellwig]

Add a iomap_bio_submit_read_endio helper factored out of
iomap_bio_submit_read to that all ->submit_read implementations for
iomap_read_ops that use iomap_bio_read_folio_range can shared the
logic.

Right now that logic is mostly trivial, but already has a bug for XFS
because the XFS version is too trivial:  file system integrity validation
needs a workqueue context and thus can't happen from the default iomap
bi_end_io I/O handler.  Unfortunately the iomap refactoring just before
fs integrity landed moved code around here and the call go misplaced,
meaning it never got called.  The PI information still is verified by
the block layer, but the offloading is less efficient (and the future
userspace interface can't get at it).

Fixes: 0b10a370529c ("iomap: support T10 protection information")
Cc: <stable@vger.kernel.org> # v7.1
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/exfat/iomap.c      |  5 +----
 fs/iomap/bio.c        | 13 ++++++++++---
 fs/ntfs/aops.c        |  6 ++----
 fs/ntfs3/inode.c      |  5 +----
 fs/xfs/xfs_aops.c     |  3 +--
 include/linux/iomap.h |  2 ++
 6 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/exfat/iomap.c b/fs/exfat/iomap.c
index 1aac38e63fe6..190fc6471f84 100644
--- a/fs/exfat/iomap.c
+++ b/fs/exfat/iomap.c
@@ -253,10 +253,7 @@ static void exfat_iomap_read_end_io(struct bio *bio)
 static void exfat_iomap_bio_submit_read(const struct iomap_iter *iter,
 		struct iomap_read_folio_ctx *ctx)
 {
-	struct bio *bio = ctx->read_ctx;
-
-	bio->bi_end_io = exfat_iomap_read_end_io;
-	submit_bio(bio);
+	iomap_bio_submit_read_endio(iter, ctx, exfat_iomap_read_end_io);
 }
 
 const struct iomap_read_ops exfat_iomap_bio_read_ops = {
diff --git a/fs/iomap/bio.c b/fs/iomap/bio.c
index 4504f4633f17..0f31e35567b4 100644
--- a/fs/iomap/bio.c
+++ b/fs/iomap/bio.c
@@ -78,15 +78,23 @@ u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend)
 	return __iomap_read_end_io(&ioend->io_bio, ioend->io_error);
 }
 
-static void iomap_bio_submit_read(const struct iomap_iter *iter,
-		struct iomap_read_folio_ctx *ctx)
+void iomap_bio_submit_read_endio(const struct iomap_iter *iter,
+		struct iomap_read_folio_ctx *ctx, bio_end_io_t end_io)
 {
 	struct bio *bio = ctx->read_ctx;
 
+	bio->bi_end_io = end_io;
 	if (iter->iomap.flags & IOMAP_F_INTEGRITY)
 		fs_bio_integrity_alloc(bio);
 	submit_bio(bio);
 }
+EXPORT_SYMBOL_GPL(iomap_bio_submit_read_endio);
+
+static void iomap_bio_submit_read(const struct iomap_iter *iter,
+		struct iomap_read_folio_ctx *ctx)
+{
+	return iomap_bio_submit_read_endio(iter, ctx, iomap_read_end_io);
+}
 
 static struct bio_set *iomap_read_bio_set(struct iomap_read_folio_ctx *ctx)
 {
@@ -127,7 +135,6 @@ static void iomap_read_alloc_bio(const struct iomap_iter *iter,
 	if (ctx->rac)
 		bio->bi_opf |= REQ_RAHEAD;
 	bio->bi_iter.bi_sector = iomap_sector(iomap, iter->pos);
-	bio->bi_end_io = iomap_read_end_io;
 	bio_add_folio_nofail(bio, folio, plen,
 			offset_in_folio(folio, iter->pos));
 	ctx->read_ctx = bio;
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 1fbf832ad165..f2bb56506046 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -38,11 +38,9 @@ static void ntfs_iomap_read_end_io(struct bio *bio)
 }
 
 static void ntfs_iomap_bio_submit_read(const struct iomap_iter *iter,
-	struct iomap_read_folio_ctx *ctx)
+		struct iomap_read_folio_ctx *ctx)
 {
-	struct bio *bio = ctx->read_ctx;
-	bio->bi_end_io = ntfs_iomap_read_end_io;
-	submit_bio(bio);
+	iomap_bio_submit_read_endio(iter, ctx, ntfs_iomap_read_end_io);
 }
 
 static const struct iomap_read_ops ntfs_iomap_bio_read_ops = {
diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
index 42af1abe17f8..f9600aba1548 100644
--- a/fs/ntfs3/inode.c
+++ b/fs/ntfs3/inode.c
@@ -609,10 +609,7 @@ static void ntfs_iomap_read_end_io(struct bio *bio)
 static void ntfs_iomap_bio_submit_read(const struct iomap_iter *iter,
 		struct iomap_read_folio_ctx *ctx)
 {
-	struct bio *bio = ctx->read_ctx;
-
-	bio->bi_end_io = ntfs_iomap_read_end_io;
-	submit_bio(bio);
+	iomap_bio_submit_read_endio(iter, ctx, ntfs_iomap_read_end_io);
 }
 
 static const struct iomap_read_ops ntfs_iomap_bio_read_ops = {
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 2a0c54256e93..51293b6f331f 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -764,8 +764,7 @@ xfs_bio_submit_read(
 
 	/* defer read completions to the ioend workqueue */
 	iomap_init_ioend(iter->inode, bio, ctx->read_ctx_file_offset, 0);
-	bio->bi_end_io = xfs_end_bio;
-	submit_bio(bio);
+	iomap_bio_submit_read_endio(iter, ctx, xfs_end_bio);
 }
 
 static const struct iomap_read_ops xfs_iomap_read_ops = {
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 3582ed1fe236..56b43d594e6e 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -622,6 +622,8 @@ extern struct bio_set iomap_ioend_bioset;
 #ifdef CONFIG_BLOCK
 int iomap_bio_read_folio_range(const struct iomap_iter *iter,
 		struct iomap_read_folio_ctx *ctx, size_t plen);
+void iomap_bio_submit_read_endio(const struct iomap_iter *iter,
+		struct iomap_read_folio_ctx *ctx, bio_end_io_t end_io);
 
 extern const struct iomap_read_ops iomap_bio_read_ops;
 
-- 
2.53.0

[PATCH 2/3] fuse: call fuse_send_readpages explicitly from fuse_readahead

[Christoph Hellwig]

From: Joanne Koong <joannelkoong@gmail.com>

Move the call to fuse_send_readpages from the iomap ->submit_read method
to the fuse readahead implementation.

fuse_read_folio() does not need to call fuse_send_readpages() because it
always does reads synchronously (the iomap->submit_read method for this
was a no-op since data->ia is always NULL for fuse_read_folio()).

This prepares for an iomap fix that will call ->submit_read after each
iomap.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/fuse/file.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e052a0d44dee..ceada75310b8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -981,19 +981,8 @@ static int fuse_iomap_read_folio_range_async(const struct iomap_iter *iter,
 	return ret;
 }
 
-static void fuse_iomap_submit_read(const struct iomap_iter *iter,
-		struct iomap_read_folio_ctx *ctx)
-{
-	struct fuse_fill_read_data *data = ctx->read_ctx;
-
-	if (data->ia)
-		fuse_send_readpages(data->ia, data->file, data->nr_bytes,
-				    data->fc->async_read);
-}
-
 static const struct iomap_read_ops fuse_iomap_read_ops = {
 	.read_folio_range = fuse_iomap_read_folio_range_async,
-	.submit_read = fuse_iomap_submit_read,
 };
 
 static int fuse_read_folio(struct file *file, struct folio *folio)
@@ -1116,6 +1105,9 @@ static void fuse_readahead(struct readahead_control *rac)
 		return;
 
 	iomap_readahead(&fuse_iomap_ops, &ctx, NULL);
+	if (data.ia)
+		fuse_send_readpages(data.ia, data.file, data.nr_bytes,
+				    fc->async_read);
 }
 
 static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
-- 
2.53.0

[PATCH 3/3] iomap: submit read bio after each extent

[Christoph Hellwig]

Currently the iomap buffered read path tries to build up read context
(i.e. bios for the typical block based case) over multiple iomaps as
long as the sector matches.  This does not take into account files
that can map to multiple different devices.  While this could be fixed
by a bdev check in iomap_bio_read_folio_range, the building up of I/O
over iomaps actually was a problem for the not yet merged ext2 iomap
port, as that does want to send out I/O at the end of an indirect
block mapped range.

So instead of adding more checks move over to a model where a bio only
spans a single iomap.  Change ->submit_read to be called after each
iteration so that the bio based users submit the bio after each iomap.
Fuse is unchanged because the previous commit stopped using ->submit_read
for it.

Fixes: dfeab2e95a75 ("erofs: add multiple device support")
Reported-by: Kelu Ye <yekelu1@huawei.com>
Reported-by: Yifan Zhao <zhaoyifan28@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Tested-by: Yifan Zhao <zhaoyifan28@huawei.com>
---
 fs/iomap/bio.c         |  2 ++
 fs/iomap/buffered-io.c | 16 ++++++++--------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/iomap/bio.c b/fs/iomap/bio.c
index 0f31e35567b4..dc8ac7e370a5 100644
--- a/fs/iomap/bio.c
+++ b/fs/iomap/bio.c
@@ -87,6 +87,8 @@ void iomap_bio_submit_read_endio(const struct iomap_iter *iter,
 	if (iter->iomap.flags & IOMAP_F_INTEGRITY)
 		fs_bio_integrity_alloc(bio);
 	submit_bio(bio);
+
+	ctx->read_ctx = NULL;
 }
 EXPORT_SYMBOL_GPL(iomap_bio_submit_read_endio);
 
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 8d4806dc46d4..276720bc18dc 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -642,12 +642,12 @@ void iomap_read_folio(const struct iomap_ops *ops,
 		fsverity_readahead(ctx->vi, folio->index,
 				   folio_nr_pages(folio));
 
-	while ((ret = iomap_iter(&iter, ops)) > 0)
+	while ((ret = iomap_iter(&iter, ops)) > 0) {
 		iter.status = iomap_read_folio_iter(&iter, ctx,
 				&bytes_submitted);
-
-	if (ctx->read_ctx && ctx->ops->submit_read)
-		ctx->ops->submit_read(&iter, ctx);
+		if (ctx->read_ctx && ctx->ops->submit_read)
+			ctx->ops->submit_read(&iter, ctx);
+	}
 
 	if (ctx->cur_folio)
 		iomap_read_end(ctx->cur_folio, bytes_submitted);
@@ -718,12 +718,12 @@ void iomap_readahead(const struct iomap_ops *ops,
 		fsverity_readahead(ctx->vi, readahead_index(rac),
 				readahead_count(rac));
 
-	while (iomap_iter(&iter, ops) > 0)
+	while (iomap_iter(&iter, ops) > 0) {
 		iter.status = iomap_readahead_iter(&iter, ctx,
 					&cur_bytes_submitted);
-
-	if (ctx->read_ctx && ctx->ops->submit_read)
-		ctx->ops->submit_read(&iter, ctx);
+		if (ctx->read_ctx && ctx->ops->submit_read)
+			ctx->ops->submit_read(&iter, ctx);
+	}
 
 	if (ctx->cur_folio)
 		iomap_read_end(ctx->cur_folio, cur_bytes_submitted);
-- 
2.53.0

Re: [PATCH 1/3] iomap: consolidate bio submission

[Christian Brauner]

On Mon, 29 Jun 2026 14:17:38 +0200, Christoph Hellwig wrote:
> Add a iomap_bio_submit_read_endio helper factored out of
> iomap_bio_submit_read to that all ->submit_read implementations for
> iomap_read_ops that use iomap_bio_read_folio_range can shared the
> logic.
> 
> Right now that logic is mostly trivial, but already has a bug for XFS
> because the XFS version is too trivial:  file system integrity validation
> needs a workqueue context and thus can't happen from the default iomap
> bi_end_io I/O handler.  Unfortunately the iomap refactoring just before
> fs integrity landed moved code around here and the call go misplaced,
> meaning it never got called.  The PI information still is verified by
> the block layer, but the offloading is less efficient (and the future
> userspace interface can't get at it).
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/3] iomap: consolidate bio submission
      https://git.kernel.org/vfs/vfs/c/044472d5ee7d
[2/3] fuse: call fuse_send_readpages explicitly from fuse_readahead
      https://git.kernel.org/vfs/vfs/c/3372eb0384b7
[3/3] iomap: submit read bio after each extent
      https://git.kernel.org/vfs/vfs/c/c1fb97d31782

Re: [PATCH 1/3] iomap: consolidate bio submission

[Christoph Hellwig]

On Wed, Jul 01, 2026 at 03:27:40PM +0200, Christian Brauner wrote:
> Applied to the vfs.fixes branch of the vfs/vfs.git tree.
> Patches in the vfs.fixes branch should appear in linux-next soon.

Hmm, both this mail and the merge commit in git reference the first
commit instead of the cower letter.  Is there an issue with your
automation that made it miss the cover letter?