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Date:   Tue,  4 Apr 2023 16:53:05 +0200
From:   Andrey Albershteyn <aalbersh@...hat.com>
To:     djwong@...nel.org, dchinner@...hat.com, ebiggers@...nel.org,
        hch@...radead.org, linux-xfs@...r.kernel.org,
        fsverity@...ts.linux.dev
Cc:     rpeterso@...hat.com, agruenba@...hat.com, xiang@...nel.org,
        chao@...nel.org, damien.lemoal@...nsource.wdc.com, jth@...nel.org,
        linux-erofs@...ts.ozlabs.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        cluster-devel@...hat.com, Andrey Albershteyn <aalbersh@...hat.com>
Subject: [PATCH v2 09/23] iomap: allow filesystem to implement read path verification

Add IOMAP_F_READ_VERITY which indicates that iomap need to
verify BIO (e.g. fs-verity) after I/O is completed.

Add iomap_readpage_ops with only optional ->prepare_ioend() to allow
filesystem to add callout used for configuring read path ioend.
Mainly for setting ->bi_end_io() callout. Add
iomap_folio_ops->verify_folio() for direct folio verification.

The verification itself is suppose to happen on filesystem side. The
verification is done when the BIO is processed by calling out
->bi_end_io().

Make iomap_read_end_io() exportable, so, it can be called back from
filesystem callout after verification is done.

The read path ioend are stored side by side with BIOs allocated from
iomap_read_ioend_bioset.

Signed-off-by: Andrey Albershteyn <aalbersh@...hat.com>
---
 fs/iomap/buffered-io.c | 32 +++++++++++++++++++++++++++++---
 include/linux/iomap.h  | 26 ++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d39be64b1da9..7e59c299c496 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -42,6 +42,7 @@ static inline struct iomap_page *to_iomap_page(struct folio *folio)
 }
 
 static struct bio_set iomap_ioend_bioset;
+static struct bio_set iomap_read_ioend_bioset;
 
 static struct iomap_page *
 iomap_page_create(struct inode *inode, struct folio *folio, unsigned int flags)
@@ -184,7 +185,7 @@ static void iomap_finish_folio_read(struct folio *folio, size_t offset,
 		folio_unlock(folio);
 }
 
-static void iomap_read_end_io(struct bio *bio)
+void iomap_read_end_io(struct bio *bio)
 {
 	int error = blk_status_to_errno(bio->bi_status);
 	struct folio_iter fi;
@@ -193,6 +194,7 @@ static void iomap_read_end_io(struct bio *bio)
 		iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
 	bio_put(bio);
 }
+EXPORT_SYMBOL_GPL(iomap_read_end_io);
 
 /**
  * iomap_read_inline_data - copy inline data into the page cache
@@ -257,6 +259,7 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 	loff_t orig_pos = pos;
 	size_t poff, plen;
 	sector_t sector;
+	struct iomap_read_ioend *ioend;
 
 	if (iomap->type == IOMAP_INLINE)
 		return iomap_read_inline_data(iter, folio);
@@ -269,6 +272,13 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 
 	if (iomap_block_needs_zeroing(iter, pos)) {
 		folio_zero_range(folio, poff, plen);
+		if (iomap->flags & IOMAP_F_READ_VERITY) {
+			if (!iomap->folio_ops->verify_folio(folio, poff, plen)) {
+				folio_set_error(folio);
+				goto done;
+			}
+		}
+
 		iomap_set_range_uptodate(folio, iop, poff, plen);
 		goto done;
 	}
@@ -290,8 +300,8 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 
 		if (ctx->rac) /* same as readahead_gfp_mask */
 			gfp |= __GFP_NORETRY | __GFP_NOWARN;
-		ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
-				     REQ_OP_READ, gfp);
+		ctx->bio = bio_alloc_bioset(iomap->bdev, bio_max_segs(nr_vecs),
+				REQ_OP_READ, GFP_NOFS, &iomap_read_ioend_bioset);
 		/*
 		 * If the bio_alloc fails, try it again for a single page to
 		 * avoid having to deal with partial page reads.  This emulates
@@ -305,6 +315,13 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 			ctx->bio->bi_opf |= REQ_RAHEAD;
 		ctx->bio->bi_iter.bi_sector = sector;
 		ctx->bio->bi_end_io = iomap_read_end_io;
+
+		ioend = container_of(ctx->bio, struct iomap_read_ioend,
+				read_inline_bio);
+		ioend->io_inode = iter->inode;
+		if (ctx->ops && ctx->ops->prepare_ioend)
+			ctx->ops->prepare_ioend(ioend);
+
 		bio_add_folio(ctx->bio, folio, plen, poff);
 	}
 
@@ -1813,6 +1830,15 @@ EXPORT_SYMBOL_GPL(iomap_writepages);
 
 static int __init iomap_init(void)
 {
+	int error = 0;
+
+	error = bioset_init(&iomap_read_ioend_bioset,
+			   4 * (PAGE_SIZE / SECTOR_SIZE),
+			   offsetof(struct iomap_read_ioend, read_inline_bio),
+			   BIOSET_NEED_BVECS);
+	if (error)
+		return error;
+
 	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
 			   offsetof(struct iomap_ioend, io_inline_bio),
 			   BIOSET_NEED_BVECS);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 0fbce375265d..9a17b53309c9 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -53,6 +53,9 @@ struct vm_fault;
  *
  * IOMAP_F_XATTR indicates that the iomap is for an extended attribute extent
  * rather than a file data extent.
+ *
+ * IOMAP_F_READ_VERITY indicates that the iomap needs verification of read
+ * folios
  */
 #define IOMAP_F_NEW		(1U << 0)
 #define IOMAP_F_DIRTY		(1U << 1)
@@ -60,6 +63,7 @@ struct vm_fault;
 #define IOMAP_F_MERGED		(1U << 3)
 #define IOMAP_F_BUFFER_HEAD	(1U << 4)
 #define IOMAP_F_XATTR		(1U << 5)
+#define IOMAP_F_READ_VERITY	(1U << 6)
 
 /*
  * Flags set by the core iomap code during operations:
@@ -156,6 +160,11 @@ struct iomap_folio_ops {
 	 * locked by the iomap code.
 	 */
 	bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);
+
+	/*
+	 * Verify folio when successfully read
+	 */
+	bool (*verify_folio)(struct folio *folio, loff_t pos, unsigned int len);
 };
 
 /*
@@ -258,13 +267,30 @@ int iomap_file_buffered_write_punch_delalloc(struct inode *inode,
 		struct iomap *iomap, loff_t pos, loff_t length, ssize_t written,
 		int (*punch)(struct inode *inode, loff_t pos, loff_t length));
 
+struct iomap_read_ioend {
+	struct inode		*io_inode;	/* file being read from */
+	struct work_struct	work;		/* post read work (e.g. fs-verity) */
+	struct bio		read_inline_bio;/* MUST BE LAST! */
+};
+
+struct iomap_readpage_ops {
+	/*
+	 * Optional, allows the file systems to perform actions just before
+	 * submitting the bio and/or override the bio bi_end_io handler for
+	 * additional verification after bio is processed
+	 */
+	void (*prepare_ioend)(struct iomap_read_ioend *ioend);
+};
+
 struct iomap_readpage_ctx {
 	struct folio			*cur_folio;
 	bool				cur_folio_in_bio;
 	struct bio			*bio;
 	struct readahead_control	*rac;
+	const struct iomap_readpage_ops *ops;
 };
 
+void iomap_read_end_io(struct bio *bio);
 int iomap_read_folio(struct iomap_readpage_ctx *ctx,
 		const struct iomap_ops *ops);
 void iomap_readahead(struct iomap_readpage_ctx *ctx,
-- 
2.38.4

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