[PATCH 05/10] block: do not reassig ->bi_bdev when partition remapping

Christoph Hellwig
2021-01-24T10:06:44Z

There is no good reason to reassign ->bi_bdev when remapping the
partition-relative block number to the device wide one, as all the
information required by the drivers comes from the gendisk anyway.

Keeping the original ->bi_bdev alive will allow to greatly simplify
the partition-away I/O accounting.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
---
block/blk-core.c | 5 +++--
include/linux/bio.h | 2 ++
include/linux/blk_types.h | 1 +
3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 64f69022de9627..1c1b97a82caa2e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -752,7 +752,7 @@ static int blk_partition_remap(struct bio *bio)
bio->bi_iter.bi_sector -
p->bd_start_sect);
}
- bio->bi_bdev = bdev_whole(p);
+ bio_set_flag(bio, BIO_REMAPPED);
return 0;
}

@@ -817,7 +817,8 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
goto end_io;
if (unlikely(bio_check_eod(bio)))
goto end_io;
- if (bio->bi_bdev->bd_partno && unlikely(blk_partition_remap(bio)))
+ if (bio->bi_bdev->bd_partno && !bio_flagged(bio, BIO_REMAPPED) &&
+ unlikely(blk_partition_remap(bio)))
goto end_io;

/*
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 12af7aa5db3778..2f1155eabaff29 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -485,6 +485,7 @@ extern const char *bio_devname(struct bio *bio, char *buffer);

#define bio_set_dev(bio, bdev) \
do { \
+ bio_clear_flag(bio, BIO_REMAPPED); \
if ((bio)->bi_bdev != (bdev)) \
bio_clear_flag(bio, BIO_THROTTLED); \
(bio)->bi_bdev = (bdev); \
@@ -493,6 +494,7 @@ do { \

#define bio_copy_dev(dst, src) \
do { \
+ bio_clear_flag(dst, BIO_REMAPPED); \
(dst)->bi_bdev = (src)->bi_bdev; \
bio_clone_blkg_association(dst, src); \
} while (0)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 8ebd8be3e05082..1bc6f6a01070fc 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -303,6 +303,7 @@ enum {
* of this bio. */
BIO_CGROUP_ACCT, /* has been accounted to a cgroup */
BIO_TRACKED, /* set if bio goes through the rq_qos path */
+ BIO_REMAPPED,
BIO_FLAG_LAST
};

--
2.29.2