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This commit fixes a bug where we are leaving the reservation in place
even though pr_release has run and returned success.
If we have a Write Exclusive, Exclusive Access, or Write/Exclusive
Registrants only reservation, the release must be sent down the path
that is the reservation holder. The problem is multipath_prepare_ioctl
most likely selected path N for the reservation, then later when we do
the release multipath_prepare_ioctl will select a completely different
path. The device will then return success becuase the nvme and scsi
specs say to return success if there is no reservation or if the
release is sent down from a path that is not the holder. We then think
we have released the reservation.
This commit has us loop over each path and send a release so we can
make sure the release is executed on the correct path. It has been
tested with windows failover clustering's validation test which checks
this case, and it has been tested manually (the libiscsi PGR tests
don't have a test case for this yet, but I will be adding one).
Signed-off-by: Mike Christie <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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When an app does a pr_reserve it will go to whatever path we happen to
be using at the time. This can result in errors when the app does a
second pr_reserve call and expects success but gets a failure because
the reserve is not done on the holder's path. This commit has us
always start trying to do reserves from the first path in the first
group.
Windows failover clustering will produce the type of pattern above.
With this commit, we will now pass its validation test for this case.
Signed-off-by: Mike Christie <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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The specs state that if you send a reserve down a path that is already
the holder success must be returned and if it goes down a path that
is not the holder reservation conflict must be returned. Windows
failover clustering will send a second reservation and expects that a
device returns success. The problem for multipathing is that for an
All Registrants reservation, we can send the reserve down any path but
for all other reservation types there is one path that is the holder.
To handle this we could add PR state to dm but that can get nasty.
Look at target_core_pr.c for an example of the type of things we'd
have to track. It will also get more complicated because other
initiators can change the state so we will have to add in async
event/sense handling.
This commit, and the 3 commits that follow, tries to keep dm simple
and keep just doing passthrough. This commit modifies dm_call_pr to be
able to find the first usable path that can execute our pr_op then
return. When dm_pr_reserve is converted to dm_call_pr in the next
commit for the normal case we will use the same path for every
reserve.
Signed-off-by: Mike Christie <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Otherwise PR ops may be issued while the broader DM device is being
reconfigured, etc.
Fixes: 9c72bad1f31a ("dm: call PR reserve/unreserve on each underlying device")
Signed-off-by: Mike Snitzer <[email protected]>
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Fault inject on pool metadata device reports:
BUG: KASAN: use-after-free in dm_pool_register_metadata_threshold+0x40/0x80
Read of size 8 at addr ffff8881b9d50068 by task dmsetup/950
CPU: 7 PID: 950 Comm: dmsetup Tainted: G W 5.19.0-rc6 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_address_description.constprop.0.cold+0xeb/0x3f4
kasan_report.cold+0xe6/0x147
dm_pool_register_metadata_threshold+0x40/0x80
pool_ctr+0xa0a/0x1150
dm_table_add_target+0x2c8/0x640
table_load+0x1fd/0x430
ctl_ioctl+0x2c4/0x5a0
dm_ctl_ioctl+0xa/0x10
__x64_sys_ioctl+0xb3/0xd0
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
This can be easily reproduced using:
echo offline > /sys/block/sda/device/state
dd if=/dev/zero of=/dev/mapper/thin bs=4k count=10
dmsetup load pool --table "0 20971520 thin-pool /dev/sda /dev/sdb 128 0 0"
If a metadata commit fails, the transaction will be aborted and the
metadata space maps will be destroyed. If a DM table reload then
happens for this failed thin-pool, a use-after-free will occur in
dm_sm_register_threshold_callback (called from
dm_pool_register_metadata_threshold).
Fix this by in dm_pool_register_metadata_threshold() by returning the
-EINVAL error if the thin-pool is in fail mode. Also fail pool_ctr()
with a new error message: "Error registering metadata threshold".
Fixes: ac8c3f3df65e4 ("dm thin: generate event when metadata threshold passed")
Cc: [email protected]
Reported-by: Hulk Robot <[email protected]>
Signed-off-by: Luo Meng <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Change dm-writecache, so that it counts the number of blocks discarded
instead of the number of discard bios. Make it consistent with the
read and write statistics counters that were changed to count the
number of blocks instead of bios.
Fixes: e3a35d03407c ("dm writecache: add event counters")
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Change dm-writecache, so that it counts the number of blocks written
instead of the number of write bios. Bios can be split and requeued
using the dm_accept_partial_bio function, so counting bios caused
inaccurate results.
Fixes: e3a35d03407c ("dm writecache: add event counters")
Reported-by: Yu Kuai <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Change dm-writecache, so that it counts the number of blocks read
instead of the number of read bios. Bios can be split and requeued
using the dm_accept_partial_bio function, so counting bios caused
inaccurate results.
Fixes: e3a35d03407c ("dm writecache: add event counters")
Reported-by: Yu Kuai <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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The functions writecache_map_remap_origin and writecache_bio_copy_ssd
only return a single value, thus they can be made to return void.
This helps simplify the following IO accounting changes.
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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dm-kcopyd doesn't access the allocated pages directly, it only passes
them to dm-io which adds them to a bio list - thus, we can allocate
the pages from high memory. This will reduce pressure on the low
memory when there are a large number of kcopyd jobs in progress.
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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dm-writecache has the capability to limit the number of writeback jobs
in progress. However, this feature was off by default. As such there
were some out-of-memory crashes observed when lowering the low
watermark while the cache is full.
This commit enables writeback limit by default. It is set to 256MiB or
1/16 of total system memory, whichever is smaller.
Cc: [email protected]
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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The status list isn't rendered as list, but rather as normal paragraph,
because there is missing blank line between "Status:" line and the list.
Fix the issue by adding the blank line separator.
Fixes: 48debafe4f2fea ("dm: add writecache target")
Signed-off-by: Bagas Sanjaya <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Otherwise this warning occurs:
Documentation/admin-guide/device-mapper/writecache.rst:23: WARNING: Unexpected indentation.
Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Signed-off-by: Zhang Jiaming <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Signed-off-by: Jiang Jian <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Replace neccessarily with necessarily.
Signed-off-by: Steven Lung <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Resolves: ERROR: else should follow close brace '}'
Signed-off-by: JeongHyeon Lee <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Rename from "tgt" to "ti" so that all of dm-table.c code uses the same
naming for dm_target variables.
Signed-off-by: Mike Snitzer <[email protected]>
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All callers of dm_table_get_target() are expected to do proper bounds
checking on the index they pass.
Move dm_table_get_target() to dm-core.h to make it extra clear that only
DM core code should be using it. Switch it to be inlined while at it.
Standardize all DM core callers to use the same for loop pattern and
make associated variables as local as possible. Rename some variables
(e.g. s/table/t/ and s/tgt/ti/) along the way.
Signed-off-by: Mike Snitzer <[email protected]>
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More efficient and readable to just access table->num_targets directly.
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Commit 61b6e2e5321d ("dm: fix BLK_STS_DM_REQUEUE handling when dm_io
represents split bio") reverted DM core's bio splitting back to using
bio_split()+bio_chain() because it was found that otherwise DM's
BLK_STS_DM_REQUEUE would trigger a live-lock waiting for bio
completion that would never occur.
Restore using bio_trim()+bio_inc_remaining(), like was done in commit
7dd76d1feec7 ("dm: improve bio splitting and associated IO
accounting"), but this time with proper handling for the above
scenario that is covered in more detail in the commit header for
61b6e2e5321d.
Solve this issue by adding a two staged dm_io requeue mechanism that
uses the new dm_bio_rewind() via dm_io_rewind():
1) requeue the dm_io into the requeue_list added to struct
mapped_device, and schedule it via new added requeue work. This
workqueue just clones the dm_io->orig_bio (which DM saves and
ensures its end sector isn't modified). dm_io_rewind() uses the
sectors and sectors_offset members of the dm_io that are recorded
relative to the end of orig_bio: dm_bio_rewind()+bio_trim() are
then used to make that cloned bio reflect the subset of the
original bio that is represented by the dm_io that is being
requeued.
2) the 2nd stage requeue is same with original requeue, but
io->orig_bio points to new cloned bio (which matches the requeued
dm_io as described above).
This allows DM core to shift the need for bio cloning from bio-split
time (during IO submission) to the less likely BLK_STS_DM_REQUEUE
handling (after IO completes with that error).
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Commit 7759eb23fd98 ("block: remove bio_rewind_iter()") removed
a similar API for the following reasons:
```
It is pointed that bio_rewind_iter() is one very bad API[1]:
1) bio size may not be restored after rewinding
2) it causes some bogus change, such as 5151842b9d8732 (block: reset
bi_iter.bi_done after splitting bio)
3) rewinding really makes things complicated wrt. bio splitting
4) unnecessary updating of .bi_done in fast path
[1] https://marc.info/?t=153549924200005&r=1&w=2
So this patch takes Kent's suggestion to restore one bio into its original
state via saving bio iterator(struct bvec_iter) in bio_integrity_prep(),
given now bio_rewind_iter() is only used by bio integrity code.
```
However, saving off a copy of the 32 bytes bio->bi_iter in case rewind
needed isn't efficient because it bloats per-bio-data for what is an
unlikely case. That suggestion also ignores the need to restore
crypto and integrity info.
Add dm_bio_rewind() API for a specific use-case that is much more narrow
than the previous more generic rewind code that was reverted:
1) most bios have a fixed end sector since bio split is done from front
of the bio, if driver just records how many sectors between current
bio's start sector and the original bio's end sector, the original
position can be restored. Keeping the original bio's end sector
fixed is a _hard_ requirement for this interface!
2) if a bio's end sector won't change (usually bio_trim() isn't
called, or in the case of DM it preserves original bio), user can
restore the original position by storing sector offset from the
current ->bi_iter.bi_sector to bio's end sector; together with
saving bio size, only 8 bytes is needed to restore to original
bio.
3) DM's requeue use case: when BLK_STS_DM_REQUEUE happens, DM core
needs to restore to an "original bio" which represents the current
dm_io to be requeued (which may be a subset of the original bio).
By storing the sector offset from the original bio's end sector and
dm_io's size, dm_bio_rewind() can restore such original bio. See
commit 7dd76d1feec7 ("dm: improve bio splitting and associated IO
accounting") for more details on how DM does this. Leveraging this,
allows DM core to shift the need for bio cloning from bio-split
time (during IO submission) to the less likely BLK_STS_DM_REQUEUE
handling (after IO completes with that error).
4) Unlike the original rewind API, dm_bio_rewind() doesn't add .bi_done
to bvec_iter and there is no effect on the fast path.
Implement dm_bio_rewind() by factoring out clear helpers that it calls:
dm_bio_integrity_rewind, dm_bio_crypt_rewind and dm_bio_rewind_iter.
DM is able to ensure that dm_bio_rewind() is used safely but, given
the constraint that the bio's end must never change, other
hypothetical future callers may not take the same care. So make
dm_bio_rewind() and all supporting code local to DM to avoid risk of
hypothetical abuse. A "dm_" prefix was added to all functions to avoid
any namespace collisions.
Suggested-by: Jens Axboe <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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If either BLK_STS_DM_REQUEUE or BLK_STS_AGAIN is returned for POLLED
io, we requeue the original bio into deferred list and kick md->wq to
re-submit it to block layer.
Improve the handling in the following way:
1) Factor out dm_handle_requeue() for handling dm_io requeue.
2) Unify handling for BLK_STS_DM_REQUEUE and BLK_STS_AGAIN: clear
REQ_POLLED for BLK_STS_DM_REQUEUE too, for the sake of simplicity,
given BLK_STS_DM_REQUEUE is very unusual.
3) Queue md->wq explicitly in dm_handle_requeue(), so requeue handling
becomes more robust.
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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The current split between dm_table_alloc_md_mempools and
dm_alloc_md_mempools is rather arbitrary, so merge the two
into one easy to follow function.
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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dm_get_reserved_rq_based_ios is only used in the core dm code, so
remove the export.
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
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Lift setting disk->ia_ranges from disk_register_independent_access_ranges
into disk_set_independent_access_ranges, and make the behavior the same
for the registered vs non-registered queue cases.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Independent access ranges only matter for file system I/O and are only
valid with a registered gendisk, so move them there.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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The configuration item BLK_RQ_IO_DATA_LEN is not declared in the kernel.
Select BLK_RQ_IO_DATA_LEN is meaningless which could be removed.
Signed-off-by: Ying Sun <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Pass a gendisk to the sysfs register/unregister functions and give
them descriptive names. Also move the unregistration helper next
to the one doing the registration.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Add a _hctx postfix to better describe what the functions do, match
the debugfs equivalents and release the old names for functions that
should be using them.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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kobject_add already grabs a reference to the parent, no need to have
another one.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Set up the default_groups for blk_queue_ktype instead of manually calling
sysfs_create_group.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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kobject_add already adds a reference to the parent that is dropped
on deletion, so don't bother grabbing another one.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Add the trace attributes to the default gendisk attributes, just like
we already do for partitions.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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blk_cleanup_disk is nothing but a trivial wrapper for put_disk now,
so remove it.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Set the queue dying flag and call blk_mq_exit_queue from del_gendisk for
all disks that do not have separately allocated queues, and thus remove
the need to call blk_cleanup_queue for them.
Rename blk_cleanup_disk to blk_mq_destroy_queue to make it clear that
this function is intended only for separately allocated blk-mq queues.
This saves an extra queue freeze for devices without a separately
allocated queue.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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These flags only apply to file system I/O, and all file system I/O is
already drained by del_gendisk and thus can't be in progress when
blk_cleanup_queue is called.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Disallow setting the blk-mq state on any queue that is already dying as
setting the state even then is a bad idea, and remove the now unused
QUEUE_FLAG_DEAD flag.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Use the proper helper to mark a surpise removal, remove the gendisk as
soon as possible when removing the device and implement the ->free_disk
callback to ensure the private data is alive as long as the gendisk has
references.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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This file is a huge mess that iterates over all devices and is in the
way of fixing the device removal in this driver, so remove it.
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Currently "blk_mq_tag_busy" return value has no effect, so adjust it.
Some code implementations have also been adjusted to enhance
readability.
Signed-off-by: Liu Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Currently, IO priority set in task's IO context is not reflected in the
bio->bi_ioprio for most IO (only io_uring and direct IO set it). This
results in odd results where process is submitting some bios with one
priority and other bios with a different (unset) priority and due to
differing priorities bios cannot be merged. Make sure bio->bi_ioprio is
always set on bio submission.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Bio's IO priority needs to be initialized before we try to merge the bio
with other bios. Otherwise we could merge bios which would otherwise
receive different IO priorities leading to possible QoS issues.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Convert blk-ioprio handling from a rqos policy to a direct call from
blk_mq_submit_bio(). Firstly, blk-ioprio is not much of a rqos policy
anyway, it just needs a hook in bio submission path to set the bio's IO
priority. Secondly, the rqos .track hook gets actually called too late
for blk-ioprio purposes and introducing a special rqos hook just for
blk-ioprio looks even weirder.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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blkcg->ioprio_set field is not really useful except for avoiding
possibly more expensive checks inside blkcg_ioprio_track(). The check
for blkcg->prio_policy being equal to POLICY_NO_CHANGE does the same
service so just remove the ioprio_set field and replace the check.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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ioprio_get(2) can be asked to return the best IO priority from several
tasks (IOPRIO_WHO_PGRP, IOPRIO_WHO_USER). Currently the call treats
tasks without set IO priority as having priority
IOPRIO_CLASS_BE/IOPRIO_BE_NORM however this does not really reflect the
IO priority the task will get (which depends on task's nice value).
Fix the code to use the real IO priority task's IO will use. We have to
modify code for ioprio_get(IOPRIO_WHO_PROCESS) to keep returning
IOPRIO_CLASS_NONE priority for tasks without set IO priority as a
special case to maintain userspace visible API.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Nobody outside of block/ioprio.c uses it.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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get_current_ioprio() operates only on current task. We will need the
same functionality for other tasks as well. Generalize
get_current_ioprio() for that and also move the bulk out of the header
file because it is large enough.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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get_current_ioprio() is used to initialize IO priority of various
requests. As such it should be returning the effective IO priority of
the task (i.e., reflecting the fact that unset IO priority should get
set based on task's CPU priority) so that the conversion is concentrated
in one place.
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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Commit e70344c05995 ("block: fix default IO priority handling")
introduced an inconsistency in get_current_ioprio() that tasks without
IO context return IOPRIO_DEFAULT priority while tasks with freshly
allocated IO context will return 0 (IOPRIO_CLASS_NONE/0) IO priority.
Tasks without IO context used to be rare before 5a9d041ba2f6 ("block:
move io_context creation into where it's needed") but after this commit
they became common because now only BFQ IO scheduler setups task's IO
context. Similar inconsistency is there for get_task_ioprio() so this
inconsistency is now exposed to userspace and userspace will see
different IO priority for tasks operating on devices with BFQ compared
to devices without BFQ. Furthemore the changes done by commit
e70344c05995 change the behavior when no IO priority is set for BFQ IO
scheduler which is also documented in ioprio_set(2) manpage:
"If no I/O scheduler has been set for a thread, then by default the I/O
priority will follow the CPU nice value (setpriority(2)). In Linux
kernels before version 2.6.24, once an I/O priority had been set using
ioprio_set(), there was no way to reset the I/O scheduling behavior to
the default. Since Linux 2.6.24, specifying ioprio as 0 can be used to
reset to the default I/O scheduling behavior."
So make sure we default to IOPRIO_CLASS_NONE as used to be the case
before commit e70344c05995. Also cleanup alloc_io_context() to
explicitely set this IO priority for the allocated IO context to avoid
future surprises. Note that we tweak ioprio_best() to maintain
ioprio_get(2) behavior and make this commit easily backportable.
CC: [email protected]
Fixes: e70344c05995 ("block: fix default IO priority handling")
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Damien Le Moal <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
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