Most DM targets will remap the clone bio passed to their ->map
function using bio_set_bdev(). So this change to pass NULL bdev to
bio_alloc_clone avoids clone-time work that sets up resources for a
bdev association that will not be used in practice (e.g. clone issued
to underlying device will not use DM device's blk-cgroups resources).

But clone->bi_bdev is still initialized following bio_alloc_clone to
preserve DM target expectations that clone->bi_bdev will be set.
Follow-up work is needed to audit DM targets to remove accesses to a
clone->bi_bdev that the target didn't initialize with bio_set_dev().

Depends-on: 7ecc56c6 ("block: allow passing a NULL bdev to bio_alloc_clone/bio_init_clone")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Fix the following coccicheck warning:

drivers/md/dm-cache-metadata.c:1512:5-6: Unneeded variable: "r".
Return "0" on line 1520.
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

The precision loss of reading IO start_time with jiffies_to_nsecs
instead of using a high resolution timer degrades HST path prediction
for BIO-based mpath on high load workloads.

Below, I show the utilization percentage of a 10 disk multipath with
asymmetrical disk access cost, while being exercised by a randwrite FIO
benchmark with high submission queue depth (depth=64).  It is possible
to see that the HST path selection degrades heavily for high-iops in
BIO-mpath, underutilizing the slower paths way beyond expected.  This
seems to be caused by the start_time truncation, which makes some IO to
seem much slower than it actually is.  In this scenario ST outperforms
HST for bio-mpath, but not for mq-mpath, which already uses ktime_get_ns().

The third column shows utilization with this patch applied.  It is easy
to see that now HST prediction is much closer to the ideal distribution
(calculated considering the real cost of each path).

|     |   ST | HST (orig) | HST(ktime) | Best |
| sdd | 0.17 |       0.20 |       0.17 | 0.18 |
| sde | 0.17 |       0.20 |       0.17 | 0.18 |
| sdf | 0.17 |       0.20 |       0.17 | 0.18 |
| sdg | 0.06 |       0.00 |       0.06 | 0.04 |
| sdh | 0.03 |       0.00 |       0.03 | 0.02 |
| sdi | 0.03 |       0.00 |       0.03 | 0.02 |
| sdj | 0.02 |       0.00 |       0.01 | 0.01 |
| sdk | 0.02 |       0.00 |       0.01 | 0.01 |
| sdl | 0.17 |       0.20 |       0.17 | 0.18 |
| sdm | 0.17 |       0.20 |       0.17 | 0.18 |

This issue was originally discussed [1] when we first merged HST, and
this patch was left as a low hanging fruit to be solved later.

Regarding the implementation, as suggested by Mike in that mail thread,
in order to avoid the overhead of ktime_get_ns for other selectors, this
patch adds a flag for the selector code to request the high-resolution
timer.

I tested this using the same benchmark used in the original HST submission.

Full test and benchmark scripts are available here:

  https://people.collabora.com/~krisman/HST-BIO-MPATH/

[1] https://lore.kernel.org/lkml/85tv0am9de.fsf@collabora.com/T/Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
[snitzer: cleaned up various implementation details]
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

The device mapper dm-crypt target is using scnprintf("%02x", cc->key[i]) to
report the current key to userspace. However, this is not a constant-time
operation and it may leak information about the key via timing, via cache
access patterns or via the branch predictor.

Change dm-crypt's key printing to use "%c" instead of "%02x". Also
introduce hex2asc() that carefully avoids any branching or memory
accesses when converting a number in the range 0 ... 15 to an ascii
character.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

The "r" variable shadows an earlier "r" that has function scope.  It
means that we accidentally return success instead of an error code.
Smatch has a warning for this:

	drivers/md/dm-integrity.c:4503 dm_integrity_ctr()
	warn: missing error code 'r'

Fixes: 7eada909 ("dm: add integrity target")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

dm-stats can be used with a very large number of entries (it is only
limited by 1/4 of total system memory), so add rescheduling points to
the loops that iterate over the entries.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Read/write/flush are the most common operations, optimize switch in
is_abnormal_io() for those cases. Follows same pattern established in
block perf-wip commit ("block: optimise blk_may_split for normal rw")

Also, push is_abnormal_io() check and blk_queue_split() down from
dm_submit_bio() to dm_split_and_process_bio() and set new
'is_abnormal_io' flag in clone_info. Optimize __split_and_process_bio
and __process_abnormal_io by leveraging ci.is_abnormal_io flag.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Now that io splitting is recorded prior to, or during, ->map IO
accounting can happen immediately rather than defer until after
bio splitting in dm_split_and_process_bio().

Remove the DM_IO_START_ACCT flag and also remove dm_io's map_task
member because there is no longer any need to wait for splitting to
occur before accounting.

Also move dm_io struct's 'flags' member to consolidate struct holes.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Now that bio_split() isn't used by DM's bio splitting, it is a bit
overkill to link dm_io into an hlist given there is only single dm_io
in the list.

Convert to using a single list for holding all dm_io instances
associated with this bio.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Currently each dm_io's reference counter is grabbed before calling
__map_bio(), this way isn't efficient since we can move this grabbing
to initialization time inside alloc_io().

Meantime it becomes typical async io reference counter model: one is
for submission side, the other is for completion side, and the io won't
be completed until both sides are done.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

dm_zone_map_bio() is only called from __map_bio in which the io's
reference is grabbed already, and the reference won't be released
until the bio is submitted, so not necessary to do it dm_zone_map_bio
any more.
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

The current DM code (ab)uses late assignment of dm_io->orig_bio (after
__map_bio() returns and any bio splitting is complete) to indicate the
FS bio has been processed and can be accounted. This results in
awkward waiting until ->orig_bio is set in dm_submit_bio_remap().

Also the bio splitting was implemented using bio_split()+bio_chain()
-- a well-worn pattern but it requires bio cloning purely for the
benefit of more natural IO accounting.  The bio_split() result was
stored in ->orig_bio to represent the mapped part of the original FS
bio.

DM has switched to the bdev based IO accounting interface.  DM's IO
accounting can be implemented in terms of the original FS bio (now
stored early in ->orig_bio) via access to its sectors/bio_op. And
if/when splitting is needed, set a new DM_IO_WAS_SPLIT flag and use
new dm_io fields of .sector_offset & .sectors to allow IO accounting
for split bios _without_ needing to clone a new bio to store in
->orig_bio.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Co-developed-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

DM splits flush with data into empty flush followed by bio with data
payload, switch dm_io_acct() to use bdev_{start,end}_io_acct() to do
this accoiunting more naturally (rather than temporarily changing the
bio's bi_size).

This will allow DM to more easily account bios that are split (in
following commit).
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

All the other 4 parameters are retrieved from the 'dm_io' instance, so
it's not necessary to pass all four to dm_io_acct().
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

dm->orig_bio is always passed to __dm_start_io_acct and dm_end_io_acct,
so it isn't necessary to take one bio parameter for the two helpers.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Rename 'bi_size' to 'bio_sectors' given bi_size is being stored in
sectors.  Also, use bio_sectors() rather than open-coding it.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Remove needless factoring and remap bi_sector regardless of
bio_sectors() being non-zero.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Use jump_labels to further reduce cost of unlikely branches for zoned
block devices, dm-stats and swap_bios throttling.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

If a bio is marked REQ_NOWAIT optimize dm_submit_bio()'s dm_table RCU
usage to dm_{get,put}_live_table_fast.

DM core offers protection against blocking (via suspend) if REQ_NOWAIT.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Just saves some cacheline bouncing for members accessed during cloned
bio submission and completion.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Avoid redundant dereferences in both functions.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Pull common DM_IO_ACCOUNTED check out to beginning of dm_start_io_acct.
Also, use dm_tio_is_normal (and move it to dm-core.h).
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Use local variable instead of redudant access using ci.io
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Also eliminate need to use errno_to_blk_status().
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

A bioset's per-cpu alloc cache may have broader utility in the future
but for now constrain it to being tightly coupled to QUEUE_FLAG_POLL.

Also change dm_io_complete() to use bio_clear_polled() so that it
properly clears all associated bio state on requeue.

This commit improves DM's hipri bio polling (REQ_POLLED) perf by
7 - 20% depending on the system.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Print the start sector and length separately instead of the combined
value to help with debugging.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220504143355.568660-1-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Device mapper wants to allocate a bio before knowing the device it
gets send to, so add explicit support for that.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Link: https://lore.kernel.org/r/20220504142950.567582-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

blkcg_bio_issue_init is called in submit_bio.  There is no need to have
extra calls that just get overriden in __bio_clone and the two places
that copy and pasted from it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Link: https://lore.kernel.org/r/20220504142950.567582-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

kthread_blkcg is only used by the built-in blk-cgroup code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-16-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Use blkcg_css instead of opencoding it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-15-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Use blkcg_css instead of open coding it, and switch to a slightly
more natural for loop.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-14-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

blkcg_css is only used in blk-cgroup.c, so move it there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-13-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Remove all the includes that aren't actually needed from
<linux/blk-cgroup.h> and push them to the actual source files where
needed.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-12-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

No need to make BLK_CGROUP stubs conditional on CONFIG_BLOCK as they
can't be used without that.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-11-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

All callers of bio_blkcg actually want the CSS, so replace it with an
interface that does return the CSS.  This now allows to move
struct blkcg_gq to block/blk-cgroup.h instead of exposing it in a
public header.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-10-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Pass the cgroup_subsys_state instead of a the blkg so that blktrace
doesn't need to poke into blk-cgroup internals, and give the name a
blk prefix as the current name is way too generic for a public
interface.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-9-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

There is no real need to expose the blkcg structure to the whole kernel.
Move it to the private header an expose a helper to let the writeback
code access the cgwb_list member.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Move these two functions out of line as there is no good reason
to inline them.  Also switch to passing a cgroup_subsys_state
instead of doing the conversion in the caller to prepare for making
the blkcg structure private to blk-cgroup.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-7-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

There is no urgent need to inline this function, so move it out of line.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-6-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>