[PATCH 02/40] btrfs: fix direct I/O read repair for split bios

[Christoph Hellwig <hch@lst.de>]

When a bio is split in btrfs_submit_direct, dip->file_offset contains
the file offset for the first bio.  But this means the start value used
in btrfs_check_read_dio_bio is incorrect for subsequent bios.  Add
a file_offset field to struct btrfs_bio to pass along the correct offset.

Given that check_data_csum only uses start of an error message this
means problems with this miscalculation will only show up when I/O
fails or checksums mismatch.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/extent_io.c |  1 +
 fs/btrfs/inode.c     | 13 +++++--------
 fs/btrfs/volumes.h   |  3 +++
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index e9fa0f6d605ee..7ca4e9b80f023 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2662,6 +2662,7 @@ int btrfs_repair_one_sector(struct inode *inode,
 
 	repair_bio = btrfs_bio_alloc(1);
 	repair_bbio = btrfs_bio(repair_bio);
+	repair_bbio->file_offset = start;
 	repair_bio->bi_opf = REQ_OP_READ;
 	repair_bio->bi_end_io = failed_bio->bi_end_io;
 	repair_bio->bi_iter.bi_sector = failrec->logical >> 9;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3ef8b63bb1b5c..93f00e9150ed0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7773,8 +7773,6 @@ static blk_status_t btrfs_check_read_dio_bio(struct btrfs_dio_private *dip,
 	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
 	struct bio_vec bvec;
 	struct bvec_iter iter;
-	const u64 orig_file_offset = dip->file_offset;
-	u64 start = orig_file_offset;
 	u32 bio_offset = 0;
 	blk_status_t err = BLK_STS_OK;
 
@@ -7784,6 +7782,8 @@ static blk_status_t btrfs_check_read_dio_bio(struct btrfs_dio_private *dip,
 		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);
 		pgoff = bvec.bv_offset;
 		for (i = 0; i < nr_sectors; i++) {
+			u64 start = bbio->file_offset + bio_offset;
+
 			ASSERT(pgoff < PAGE_SIZE);
 			if (uptodate &&
 			    (!csum || !check_data_csum(inode, bbio,
@@ -7796,17 +7796,13 @@ static blk_status_t btrfs_check_read_dio_bio(struct btrfs_dio_private *dip,
 			} else {
 				int ret;
 
-				ASSERT((start - orig_file_offset) < UINT_MAX);
-				ret = btrfs_repair_one_sector(inode,
-						&bbio->bio,
-						start - orig_file_offset,
-						bvec.bv_page, pgoff,
+				ret = btrfs_repair_one_sector(inode, &bbio->bio,
+						bio_offset, bvec.bv_page, pgoff,
 						start, bbio->mirror_num,
 						submit_dio_repair_bio);
 				if (ret)
 					err = errno_to_blk_status(ret);
 			}
-			start += sectorsize;
 			ASSERT(bio_offset + sectorsize > bio_offset);
 			bio_offset += sectorsize;
 			pgoff += sectorsize;
@@ -8009,6 +8005,7 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 		bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len);
 		bio->bi_private = dip;
 		bio->bi_end_io = btrfs_end_dio_bio;
+		btrfs_bio(bio)->file_offset = file_offset;
 
 		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 			status = extract_ordered_extent(BTRFS_I(inode), bio,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 005c9e2a491a1..c22148bebc2f5 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -323,6 +323,9 @@ struct btrfs_fs_devices {
 struct btrfs_bio {
 	unsigned int mirror_num;
 
+	/* for direct I/O */
+	u64 file_offset;
+
 	/* @device is for stripe IO submission. */
 	struct btrfs_device *device;
 	u8 *csum;
-- 
2.30.2