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dm: add dm_submit_bio_remap interface

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Where possible, switch from early bio-based IO accounting (at the time
DM clones each incoming bio) to late IO accounting just before each
remapped bio is issued to underlying device via submit_bio_noacct().

Allows more precise bio-based IO accounting for DM targets that use
their own workqueues to perform additional processing of each bio in
conjunction with their DM_MAPIO_SUBMITTED return from their map
function. When a target is updated to use dm_submit_bio_remap() they
must also set ti->accounts_remapped_io to true.

Use xchg() in start_io_acct(), as suggested by Mikulas, to ensure each
IO is only started once.  The xchg race only happens if
__send_duplicate_bios() sends multiple bios -- that case is reflected
via tio->is_duplicate_bio.  Given the niche nature of this race, it is
best to avoid any xchg performance penalty for normal IO.

For IO that was never submitted with dm_bio_submit_remap(), but the
target completes the clone with bio_endio, accounting is started then
ended and pending_io counter decremented.

Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer
2022-02-17 23:40:32 -05:00
parent e6fc9f62ce
commit 0fbb4d93b3
4 changed files with 118 additions and 22 deletions
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4
include/uapi/linux/dm-ioctl.h
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@@ -286,9 +286,9 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
#define DM_VERSION_MINOR 45
#define DM_VERSION_MINOR 46
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2021-03-22)"
#define DM_VERSION_EXTRA "-ioctl (2022-02-22)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */