iomap: teach iomap to read files with fsverity

Obtain fsverity info for folios with file data and fsverity metadata.
Filesystem can pass vi down to ioend and then to fsverity for
verification. This is different from other filesystems ext4, f2fs, btrfs
supporting fsverity, these filesystems don't need fsverity_info for
reading fsverity metadata. While reading merkle tree iomap requires
fsverity info to synthesize hashes for zeroed data block.

fsverity metadata has two kinds of holes - ones in merkle tree and one
after fsverity descriptor.

Merkle tree holes are blocks full of hashes of zeroed data blocks. These
are not stored on the disk but synthesized on the fly. This saves a bit
of space for sparse files. Due to this iomap also need to lookup
fsverity_info for folios with fsverity metadata. ->vi has a hash of the
zeroed data block which will be used to fill the merkle tree block.

The hole past descriptor is interpreted as end of metadata region. As we
don't have EOF here we use this hole as an indication that rest of the
folio is empty. This patch marks rest of the folio beyond fsverity
descriptor as uptodate.

For file data, fsverity needs to verify consistency of the whole file
against the root hash, hashes of holes are included in the merkle tree.
Verify them too.

Issue reading of fsverity merkle tree on the fsverity inodes. This way
metadata will be available at I/O completion time.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
Link: https://patch.msgid.link/20260520123722.405752-9-aalbersh@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 5b2b40e81b61..1be2e16b696a 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -429,6 +429,7 @@ struct iomap_ioend {
 	loff_t			io_offset;	/* offset in the file */
 	sector_t		io_sector;	/* start sector of ioend */
 	void			*io_private;	/* file system private data */
+	struct fsverity_info	*io_vi;		/* fsverity info */
 	struct bio		io_bio;		/* MUST BE LAST! */
 };
 
@@ -503,6 +504,7 @@ struct iomap_read_folio_ctx {
 	struct readahead_control *rac;
 	void			*read_ctx;
 	loff_t			read_ctx_file_offset;
+	struct fsverity_info	*vi;
 };
 
 struct iomap_read_ops {