[PATCH v3 12/28] iomap: allow filesystem to implement read path verification

Andrey Albershteyn
2023-10-06T18:55:17Z

Currently, there is no interface to let filesystem do
post-processing of completed BIO (ioend) in read path. This can be
very handy for fs-verity verification. This patch add a callout to
filesystem provided ->submit_bio to configure BIO completion callout.

The read path ioend iomap_read_ioend are stored side by side with
BIOs allocated from filesystem provided bio_set.

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

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

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
---
fs/iomap/buffered-io.c | 40 +++++++++++++++++++++++++++++++++-------
include/linux/iomap.h | 15 +++++++++++++++
2 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ca78c7f62527..0a1bec91fdf6 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -332,6 +332,19 @@ static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
pos >= i_size_read(iter->inode);
}

+static void
+iomap_submit_read_io(const struct iomap_iter *iter,
+ struct iomap_readpage_ctx *ctx)
+{
+ if (!ctx->bio)
+ return;
+
+ if (ctx->ops && ctx->ops->submit_io)
+ ctx->ops->submit_io(iter, ctx->bio, iter->pos);
+ else
+ submit_bio(ctx->bio);
+}
+
static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
struct iomap_readpage_ctx *ctx, loff_t offset)
{
@@ -355,6 +368,13 @@ 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 (ctx->ops->verify_folio(folio, poff, plen)) {
+ folio_set_error(folio);
+ goto done;
+ }
+ }
+
iomap_set_range_uptodate(folio, poff, plen);
goto done;
}
@@ -371,13 +391,20 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
gfp_t orig_gfp = gfp;
unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);

- if (ctx->bio)
- submit_bio(ctx->bio);
+ iomap_submit_read_io(iter, ctx);

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);
+
+ if (ctx->ops && ctx->ops->bio_set)
+ ctx->bio = bio_alloc_bioset(iomap->bdev,
+ bio_max_segs(nr_vecs),
+ REQ_OP_READ, GFP_NOFS,
+ ctx->ops->bio_set);
+ else
+ ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
+ REQ_OP_READ, gfp);
+
/*
* If the bio_alloc fails, try it again for a single page to
* avoid having to deal with partial page reads. This emulates
@@ -427,7 +454,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops,
folio_set_error(folio);

if (ctx.bio) {
- submit_bio(ctx.bio);
+ iomap_submit_read_io(&iter, &ctx);
WARN_ON_ONCE(!ctx.cur_folio_in_bio);
} else {
WARN_ON_ONCE(ctx.cur_folio_in_bio);
@@ -502,8 +529,7 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops,
while (iomap_iter(&iter, ops) > 0)
iter.processed = iomap_readahead_iter(&iter, &ctx);

- if (ctx.bio)
- submit_bio(ctx.bio);
+ iomap_submit_read_io(&iter, &ctx);
if (ctx.cur_folio) {
if (!ctx.cur_folio_in_bio)
folio_unlock(ctx.cur_folio);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 3565c449f3c9..8d7206cd2f0f 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)
@@ -64,6 +67,7 @@ struct vm_fault;
#define IOMAP_F_BUFFER_HEAD 0
#endif /* CONFIG_BUFFER_HEAD */
#define IOMAP_F_XATTR (1U << 5)
+#define IOMAP_F_READ_VERITY (1U << 6)

/*
* Flags set by the core iomap code during operations:
@@ -262,7 +266,18 @@ 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, verify folio when successfully read
+ */
+ int (*verify_folio)(struct folio *folio, loff_t pos, unsigned int len);
+
/*
* Filesystems wishing to attach private information to a direct io bio
* must provide a ->submit_io method that attaches the additional
--
2.40.1