[PATCH 06/22] block,iomap: fix protection information verification with initial bvec offset

[Christoph Hellwig <hch@lst.de>]

When reconstructing a bvec_iter from an ioend for protection information
verification, iomap currently ignores the offset into the initial
bio_vec.

This can't happen for buffered I/O an direct I/O to user addresses, but
is exercised by split on O_DIRECT file descriptors or when using the loop
driver.

Fortunately the only file system PI user (XFS) currently always bounce
buffers, so this can't actually be triggered yet.  But we'll want to make
the bounce buffering conditional soon, for which this needs to be fixed.

Store the initial offset in struct iomap_ioend, and pass a
pre-constructed bvec_iter to fs_bio_integrity_verify.  For the
synchronous read case the fix is even simpler as this path can
simply stash away the original bvec_iter.

Fixes: 0bde8a12b554 ("block: add fs_bio_integrity helpers")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio-integrity-fs.c      | 13 +++++--------
 fs/iomap/bio.c                |  4 +++-
 fs/iomap/ioend.c              | 14 ++++++++++----
 include/linux/bio-integrity.h |  3 +--
 include/linux/iomap.h         |  8 ++++++++
 5 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/block/bio-integrity-fs.c b/block/bio-integrity-fs.c
index 692403dfa047..dd6c85530913 100644
--- a/block/bio-integrity-fs.c
+++ b/block/bio-integrity-fs.c
@@ -52,14 +52,10 @@ void fs_bio_integrity_generate(struct bio *bio)
 }
 EXPORT_SYMBOL_GPL(fs_bio_integrity_generate);
 
-int fs_bio_integrity_verify(struct bio *bio, sector_t sector, unsigned int size)
+int fs_bio_integrity_verify(struct bio *bio, struct bvec_iter *data_iter)
 {
 	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
 	struct bio_integrity_payload *bip = bio_integrity(bio);
-	struct bvec_iter data_iter = {
-		.bi_sector	= sector,
-		.bi_size	= size,
-	};
 
 	if (!bip || !(bip->bip_flags & BIP_CHECK_FLAGS))
 		return 0;
@@ -71,9 +67,10 @@ int fs_bio_integrity_verify(struct bio *bio, sector_t sector, unsigned int size)
 	 * bio.  Requires the submitter to remember the sector and the size.
 	 */
 	memset(&bip->bip_iter, 0, sizeof(bip->bip_iter));
-	bip->bip_iter.bi_sector = sector;
-	bip->bip_iter.bi_size = bio_integrity_bytes(bi, size >> SECTOR_SHIFT);
-	return blk_status_to_errno(bio_integrity_verify(bio, &data_iter));
+	bip->bip_iter.bi_sector = data_iter->bi_sector;
+	bip->bip_iter.bi_size =
+		bio_integrity_bytes(bi, data_iter->bi_size >> SECTOR_SHIFT);
+	return blk_status_to_errno(bio_integrity_verify(bio, data_iter));
 }
 
 static int __init fs_bio_integrity_init(void)
diff --git a/fs/iomap/bio.c b/fs/iomap/bio.c
index 30ef78a66b4f..813002b2299d 100644
--- a/fs/iomap/bio.c
+++ b/fs/iomap/bio.c
@@ -169,6 +169,7 @@ int iomap_bio_read_folio_range_sync(const struct iomap_iter *iter,
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	sector_t sector = iomap_sector(srcmap, pos);
+	struct bvec_iter saved_iter;
 	struct bio_vec bvec;
 	struct bio bio;
 	int error;
@@ -178,10 +179,11 @@ int iomap_bio_read_folio_range_sync(const struct iomap_iter *iter,
 	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
 	if (srcmap->flags & IOMAP_F_INTEGRITY)
 		fs_bio_integrity_alloc(&bio);
+	saved_iter = bio.bi_iter;
 	error = submit_bio_wait(&bio);
 	if (bio_integrity(&bio)) {
 		if (!error)
-			error = fs_bio_integrity_verify(&bio, sector, len);
+			error = fs_bio_integrity_verify(&bio, &saved_iter);
 		fs_bio_integrity_free(&bio);
 	}
 	return error;
diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
index 2ec755a89228..d43e6229900c 100644
--- a/fs/iomap/ioend.c
+++ b/fs/iomap/ioend.c
@@ -25,6 +25,7 @@ struct iomap_ioend *iomap_init_ioend(struct inode *inode,
 	ioend->io_parent = NULL;
 	INIT_LIST_HEAD(&ioend->io_list);
 	ioend->io_flags = ioend_flags;
+	ioend->io_bvec_offset = bio->bi_iter.bi_bvec_done;
 	ioend->io_inode = inode;
 	ioend->io_offset = file_offset;
 	ioend->io_size = bio->bi_iter.bi_size;
@@ -311,6 +312,13 @@ ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, struct folio *folio,
 }
 EXPORT_SYMBOL_GPL(iomap_add_to_ioend);
 
+static int iomap_ioend_integrity_verify(struct iomap_ioend *ioend)
+{
+	struct bvec_iter data_iter = BVEC_ITER_IOEND(ioend);
+
+	return fs_bio_integrity_verify(&ioend->io_bio, &data_iter);
+}
+
 static u32 iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 {
 	if (ioend->io_parent) {
@@ -328,10 +336,8 @@ static u32 iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 
 	if (!ioend->io_error &&
 	    bio_integrity(&ioend->io_bio) &&
-	    bio_op(&ioend->io_bio) == REQ_OP_READ) {
-		ioend->io_error = fs_bio_integrity_verify(&ioend->io_bio,
-			ioend->io_sector, ioend->io_size);
-	}
+	    bio_op(&ioend->io_bio) == REQ_OP_READ)
+		ioend->io_error = iomap_ioend_integrity_verify(ioend);
 
 	if (ioend->io_flags & IOMAP_IOEND_DIRECT)
 		return iomap_finish_ioend_direct(ioend);
diff --git a/include/linux/bio-integrity.h b/include/linux/bio-integrity.h
index 0ea2a8bf7efb..a954c97be0b3 100644
--- a/include/linux/bio-integrity.h
+++ b/include/linux/bio-integrity.h
@@ -151,7 +151,6 @@ void bio_integrity_setup_default(struct bio *bio);
 unsigned int fs_bio_integrity_alloc(struct bio *bio);
 void fs_bio_integrity_free(struct bio *bio);
 void fs_bio_integrity_generate(struct bio *bio);
-int fs_bio_integrity_verify(struct bio *bio, sector_t sector,
-		unsigned int size);
+int fs_bio_integrity_verify(struct bio *bio, struct bvec_iter *data_iter);
 
 #endif /* _LINUX_BIO_INTEGRITY_H */
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 56b43d594e6e..e7bee96379df 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -424,6 +424,7 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
 struct iomap_ioend {
 	struct list_head	io_list;	/* next ioend in chain */
 	u16			io_flags;	/* IOMAP_IOEND_* */
+	u32			io_bvec_offset;	/* offset into first bvec */
 	struct inode		*io_inode;	/* file being written to */
 	size_t			io_size;	/* size of the extent */
 	atomic_t		io_remaining;	/* completetion defer count */
@@ -441,6 +442,13 @@ static inline struct iomap_ioend *iomap_ioend_from_bio(struct bio *bio)
 	return container_of(bio, struct iomap_ioend, io_bio);
 }
 
+#define BVEC_ITER_IOEND(_ioend)				\
+{							\
+	.bi_sector	= (_ioend)->io_sector,		\
+	.bi_size	= (_ioend)->io_size,		\
+	.bi_bvec_done	= (_ioend)->io_bvec_offset,	\
+}
+
 struct iomap_writeback_ops {
 	/*
 	 * Performs writeback on the passed in range
-- 
2.53.0