Commit Graph

303 Commits

Author SHA1 Message Date
Breno Leitao
ee7ff15bf5 elevator: Remove argument from elevator_find_get
Commit e4eb37cc0f ("block: Remove elevator required features")
removed the usage of `struct request_queue` from elevator_find_get(),
but didn't removed the argument.

Remove the "struct request_queue *q" argument from elevator_find_get()
given it is useless.

Fixes: e4eb37cc0f ("block: Remove elevator required features")
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20241011155615.3361143-1-leitao@debian.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-11 11:11:09 -06:00
Breno Leitao
b4ff6e93bf elevator: do not request_module if elevator exists
Whenever an I/O elevator is changed, the system attempts to load a
module for the new elevator. This occurs regardless of whether the
elevator is already loaded or built directly into the kernel. This
behavior introduces unnecessary overhead and potential issues.

This makes the operation slower, and more error-prone. For instance,
making the problem fixed by [1] visible for users that doesn't even rely
on modules being available through modules.

Do not try to load the ioscheduler if it is already visible.

This change brings two main benefits: it improves the performance of
elevator changes, and it reduces the likelihood of errors occurring
during this process.

[1] Commit e3accac1a9 ("block: Fix elv_iosched_local_module handling of "none" scheduler")

Fixes: 734e1a8603 ("block: Prevent deadlocks when switching elevators")
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20241011170122.3880087-1-leitao@debian.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-11 11:10:52 -06:00
SurajSonawane2415
b402328a24 block: Fix elevator_get_default() checking for NULL q->tag_set
elevator_get_default() and elv_support_iosched() both check for whether
or not q->tag_set is non-NULL, however it's not possible for them to be
NULL. This messes up some static checkers, as the checking of tag_set
isn't consistent.

Remove the checks, which both simplifies the logic and avoids checker
errors.

Signed-off-by: SurajSonawane2415 <surajsonawane0215@gmail.com>
Link: https://lore.kernel.org/r/20241007111416.13814-1-surajsonawane0215@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-07 14:24:36 -06:00
Damien Le Moal
e3accac1a9 block: Fix elv_iosched_local_module handling of "none" scheduler
Commit 734e1a8603 ("block: Prevent deadlocks when switching
elevators") introduced the function elv_iosched_load_module() to allow
loading an elevator module outside of elv_iosched_store() with the
target device queue not frozen, to avoid deadlocks. However, the "none"
scheduler does not have a module and as a result,
elv_iosched_load_module() always returns an error when trying to switch
to this valid scheduler.

Fix this by ignoring the return value of the request_module() call
done by elv_iosched_load_module(). This restores the behavior before
commit 734e1a8603, which was to ignore the request_module() result and
instead rely on elevator_change() to handle the "none" scheduler case.

Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 734e1a8603 ("block: Prevent deadlocks when switching elevators")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240917133231.134806-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-09-17 08:34:00 -06:00
Damien Le Moal
734e1a8603 block: Prevent deadlocks when switching elevators
Commit af28141498 ("block: freeze the queue in queue_attr_store")
changed queue_attr_store() to always freeze a sysfs attribute queue
before calling the attribute store() method, to ensure that no IOs are
in-flight when an attribute value is being updated.

However, this change created a potential deadlock situation for the
scheduler queue attribute as changing the queue elevator with
elv_iosched_store() can result in a call to request_module() if the user
requested module is not already registered. If the file of the requested
module is stored on the block device of the frozen queue, a deadlock
will happen as the read operations triggered by request_module() will
wait for the queue freeze to end.

Solve this issue by introducing the load_module method in struct
queue_sysfs_entry, and to calling this method function in
queue_attr_store() before freezing the attribute queue.
The macro definition QUEUE_RW_LOAD_MODULE_ENTRY() is added to define a
queue sysfs attribute that needs loading a module.

The definition of the scheduler atrribute is changed to using
QUEUE_RW_LOAD_MODULE_ENTRY(), with the function
elv_iosched_load_module() defined as the load_module method.
elv_iosched_store() can then be simplified to remove the call to
request_module().

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Reported-by: Jiri Jaburek <jjaburek@redhat.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219166
Fixes: af28141498 ("block: freeze the queue in queue_attr_store")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Link: https://lore.kernel.org/r/20240908000704.414538-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-09-10 13:43:42 -06:00
Christoph Hellwig
62e35f9422 block: pass a gendisk to the queue_sysfs_entry methods
The kobject for the queue entries is embedded into a struct gendisk.
Pass it to the sysfs methods instead of the request_queue derived from
it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240627111407.476276-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-06-28 15:06:16 -06:00
Damien Le Moal
e4eb37cc0f block: Remove elevator required features
The only elevator feature ever implemented is ELEVATOR_F_ZBD_SEQ_WRITE
for signaling that a scheduler implements zone write locking to tightly
control the dispatching order of write operations to zoned block
devices. With the removal of zone write locking support in mq-deadline
and the reliance of all block device drivers on the block layer zone
write plugging to control ordering of write operations to zones, the
elevator feature ELEVATOR_F_ZBD_SEQ_WRITE is completely unused.
Remove it, and also remove the now unused code for filtering the
possible schedulers for a block device based on required features.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240408014128.205141-23-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-04-17 08:44:03 -06:00
Chengming Zhou
e5c0ca1365 blk-mq: release scheduler resource when request completes
Chuck reported [1] an IO hang problem on NFS exports that reside on SATA
devices and bisected to commit 615939a2ae ("blk-mq: defer to the normal
submission path for post-flush requests").

We analysed the IO hang problem, found there are two postflush requests
waiting for each other.

The first postflush request completed the REQ_FSEQ_DATA sequence, so go to
the REQ_FSEQ_POSTFLUSH sequence and added in the flush pending list, but
failed to blk_kick_flush() because of the second postflush request which
is inflight waiting in scheduler queue.

The second postflush waiting in scheduler queue can't be dispatched because
the first postflush hasn't released scheduler resource even though it has
completed by itself.

Fix it by releasing scheduler resource when the first postflush request
completed, so the second postflush can be dispatched and completed, then
make blk_kick_flush() succeed.

While at it, remove the check for e->ops.finish_request, as all
schedulers set that. Reaffirm this requirement by adding a WARN_ON_ONCE()
at scheduler registration time, just like we do for insert_requests and
dispatch_request.

[1] https://lore.kernel.org/all/7A57C7AE-A51A-4254-888B-FE15CA21F9E9@oracle.com/

Link: https://lore.kernel.org/linux-block/20230819031206.2744005-1-chengming.zhou@linux.dev/
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202308172100.8ce4b853-oliver.sang@intel.com
Fixes: 615939a2ae ("blk-mq: defer to the normal submission path for post-flush requests")
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/20230813152325.3017343-1-chengming.zhou@linux.dev
[axboe: folded in incremental fix and added tags]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-08-19 07:47:17 -06:00
Azeem Shaikh
20d099756b block: Replace all non-returning strlcpy with strscpy
strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230530155608.272266-1-azeemshaikh38@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-01 09:13:31 -06:00
Thomas Weißschuh
5f6224175f block: make kobj_type structures constant
Since commit ee6d3dd4ed ("driver core: make kobj_type constant.")
the driver core allows the usage of const struct kobj_type.

Take advantage of this to constify the structure definitions to prevent
modification at runtime.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20230208-kobj_type-block-v1-1-0b3eafd7d983@weissschuh.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-02-09 09:38:16 -07:00
Christoph Hellwig
2bd85221a6 block: untangle request_queue refcounting from sysfs
The kobject embedded into the request_queue is used for the queue
directory in sysfs, but that is a child of the gendisks directory and is
intimately tied to it.  Move this kobject to the gendisk and use a
refcount_t in the request_queue for the actual request_queue refcounting
that is completely unrelated to the device model.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221114042637.1009333-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-30 11:09:00 -07:00
Jinlong Chen
8d283ee62b block: use bool as the return type of elv_iosched_allow_bio_merge
We have bool type now, update the old signature.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/0db0a0298758d60d0f4df8b7126ac6a381e5a5bb.1669736350.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-29 10:53:10 -07:00
Jinlong Chen
c6451ede40 block: replace "len+name" with "name+len" in elv_iosched_show
The "pointer + offset" pattern is more resonable.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/d9beaee71b14f7b2a39ab0db6458dc0f7d961ceb.1669736350.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-29 10:53:10 -07:00
Jinlong Chen
7a3b3660fd block: always use 'e' when printing scheduler name
Printing e->elevator_name in all cases improves the readability, and
'e' and 'cur' are identical in this branch.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Link: https://lore.kernel.org/r/4bae180ffbac608ea0cf46ffa9739ce0973b60aa.1669736350.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-29 10:53:10 -07:00
Jinlong Chen
5998249e32 block: replace continue with else-if in elv_iosched_show
else-if is more readable than continue here.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Link: https://lore.kernel.org/r/77ac19ba556efd2c8639a6396eb4203c59bc13d6.1669736350.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-29 10:53:06 -07:00
Jinlong Chen
7919d679ae block: include 'none' for initial elv_iosched_show call
This makes the printing order of the io schedulers consistent, and removes
a redundant q->elevator check.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/bdd7083ed4f232e3285f39081e3c5f30b20b8da2.1669736350.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-29 10:48:59 -07:00
Jinlong Chen
4284354758 elevator: remove an outdated comment in elevator_change
mq is no longer a special case.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/cbf47824fc726440371e74c867bf635ae1b671a3.1669126766.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-23 06:48:20 -07:00
Jinlong Chen
f69b5e8f35 elevator: update the document of elevator_match
elevator_match does not care about elevator_features any more. Remove
related descriptions from its document.

Fixes: ffb86425ee ("block: don't check for required features in elevator_match")
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/a58424555202c07a9ccf7f60c3ad7e247da09e25.1669126766.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-23 06:48:20 -07:00
Jinlong Chen
e0cca8bc9c elevator: printk a warning if switching to a new io scheduler fails
printk a warning to indicate that the io scheduler has been set to none
if switching to a new io scheduler fails.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/d51ed0fb457db7a4f9cbb0dbce36d534e22be457.1669126766.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-23 06:48:08 -07:00
Jinlong Chen
ac1171bd2c elevator: update the document of elevator_switch
We no longer support falling back to the old io scheduler if switching to
the new one fails. Update the document to indicate that.

Fixes: a1ce35fa49 ("block: remove dead elevator code")
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/94250961689ba7d2e67a7d9e7995a11166fedb31.1669126766.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-23 06:47:46 -07:00
Yang Li
5b2560c4c2 block: Fix some kernel-doc comments
Remove the description of @required_features in elevator_match()
to clear the below warning:

block/elevator.c:103: warning: Excess function parameter 'required_features' description in 'elevator_match'

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2734
Fixes: ffb86425ee ("block: don't check for required features in elevator_match")
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221107062255.2685-1-yang.lee@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-07 07:21:45 -07:00
Christoph Hellwig
64b36075eb block: split elevator_switch
Split an elevator_disable helper from elevator_switch for the case where
we want to switch to no scheduler at all.  This includes removing the
pointless elevator_switch_mq helper and removing the switch to no
schedule logic from blk_mq_init_sched.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 09:12:24 -06:00
Christoph Hellwig
ffb86425ee block: don't check for required features in elevator_match
Checking for the required features in the callers simplifies the code
quite a bit, so do that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-7-hch@lst.de
[axboe: adjust for dropping patch 1, use __elevator_find()]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 09:12:05 -06:00
Christoph Hellwig
2eef17a209 block: simplify the check for the current elevator in elv_iosched_show
Just compare the pointers instead of using the string based
elevator_match.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 08:02:47 -06:00
Christoph Hellwig
16095af2fa block: cleanup the variable naming in elv_iosched_store
Use eq for the elevator_queue as done elsewhere.  This frees e to be used
for the loop iterator instead of the odd __ prefix.  In addition rename
elv to cur to make it more clear it is the currently selected elevator.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 08:02:47 -06:00
Christoph Hellwig
aae2a643f5 block: exit elv_iosched_show early when I/O schedulers are not supported
If the tag_set has BLK_MQ_F_NO_SCHED flag set we will never show any
scheduler, so exit early.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 08:02:47 -06:00
Christoph Hellwig
81eaca442e block: cleanup elevator_get
Do the request_module and repeated lookup in the only caller that cares,
pick a saner name that explains where are actually doing a lookup and
use a sane calling conventions that passes the queue first.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221030100714.876891-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01 08:02:47 -06:00
Jinlong Chen
8ed40ee35d block: fix up elevator_type refcounting
The current reference management logic of io scheduler modules contains
refcnt problems. For example, blk_mq_init_sched may fail before or after
the calling of e->ops.init_sched. If it fails before the calling, it does
nothing to the reference to the io scheduler module. But if it fails after
the calling, it releases the reference by calling kobject_put(&eq->kobj).

As the callers of blk_mq_init_sched can't know exactly where the failure
happens, they can't handle the reference to the io scheduler module
properly: releasing the reference on failure results in double-release if
blk_mq_init_sched has released it, and not releasing the reference results
in ghost reference if blk_mq_init_sched did not release it either.

The same problem also exists in io schedulers' init_sched implementations.

We can address the problem by adding releasing statements to the error
handling procedures of blk_mq_init_sched and init_sched implementations.
But that is counterintuitive and requires modifications to existing io
schedulers.

Instead, We make elevator_alloc get the io scheduler module references
that will be released by elevator_release. And then, we match each
elevator_get with an elevator_put. Therefore, each reference to an io
scheduler module explicitly has its own getter and releaser, and we no
longer need to worry about the refcnt problems.

The bugs and the patch can be validated with tools here:
https://github.com/nickyc975/linux_elv_refcnt_bug.git

[hch: split out a few bits into separate patches, use a non-try
      module_get in elevator_alloc]

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221020064819.1469928-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Jinlong Chen
b54c2ad9b7 block: check for an unchanged elevator earlier in __elevator_change
No need to find the actual elevator_type struct for this comparism,
the name is all that is needed.

Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
[hch: split from a larger patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221020064819.1469928-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Christoph Hellwig
58367c8a5f block: sanitize the elevator name before passing it to __elevator_change
The stripped name should also be used for the none check.  To do so
strip it in the caller and pass in the sanitized name.  Drop the pointless
__ prefix in the function name while we're at it.

Based on a patch from Jinlong Chen <nickyc975@zju.edu.cn>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221020064819.1469928-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Christoph Hellwig
dd6f7f17bf block: add proper helpers for elevator_type module refcount management
Make sure we have helpers for all relevant module refcount operations on
the elevator_type in elevator.h, and use them.  Move the call to the get
helper in blk_mq_elv_switch_none a bit so that it is obvious with a less
verbose comment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221020064819.1469928-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Yu Kuai
181d066374 elevator: add new field flags in struct elevator_queue
There are only one flag to indicate that elevator is registered currently,
prepare to add a flag to disable wbt if default elevator is bfq.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221019121518.3865235-6-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Yu Kuai
6d9f4cf125 elevator: remove redundant code in elv_unregister_queue()
"elevator_queue *e" is already declared and initialized in the beginning
of elv_unregister_queue().

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221019121518.3865235-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-23 18:59:17 -06:00
Keith Busch
8237c01f16 blk-mq: use quiesced elevator switch when reinitializing queues
The hctx's run_work may be racing with the elevator switch when
reinitializing hardware queues. The queue is merely frozen in this
context, but that only prevents requests from allocating and doesn't
stop the hctx work from running. The work may get an elevator pointer
that's being torn down, and can result in use-after-free errors and
kernel panics (example below). Use the quiesced elevator switch instead,
and make the previous one static since it is now only used locally.

  nvme nvme0: resetting controller
  nvme nvme0: 32/0/0 default/read/poll queues
  BUG: kernel NULL pointer dereference, address: 0000000000000008
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 80000020c8861067 P4D 80000020c8861067 PUD 250f8c8067 PMD 0
  Oops: 0000 [#1] SMP PTI
  Workqueue: kblockd blk_mq_run_work_fn
  RIP: 0010:kyber_has_work+0x29/0x70

...

  Call Trace:
   __blk_mq_do_dispatch_sched+0x83/0x2b0
   __blk_mq_sched_dispatch_requests+0x12e/0x170
   blk_mq_sched_dispatch_requests+0x30/0x60
   __blk_mq_run_hw_queue+0x2b/0x50
   process_one_work+0x1ef/0x380
   worker_thread+0x2d/0x3e0

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220927155652.3260724-1-kbusch@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-09-27 09:58:56 -06:00
Linus Torvalds
616355cc81 for-5.18/block-2022-03-18
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Merge tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:

 - BFQ cleanups and fixes (Yu, Zhang, Yahu, Paolo)

 - blk-rq-qos completion fix (Tejun)

 - blk-cgroup merge fix (Tejun)

 - Add offline error return value to distinguish it from an IO error on
   the device (Song)

 - IO stats fixes (Zhang, Christoph)

 - blkcg refcount fixes (Ming, Yu)

 - Fix for indefinite dispatch loop softlockup (Shin'ichiro)

 - blk-mq hardware queue management improvements (Ming)

 - sbitmap dead code removal (Ming, John)

 - Plugging merge improvements (me)

 - Show blk-crypto capabilities in sysfs (Eric)

 - Multiple delayed queue run improvement (David)

 - Block throttling fixes (Ming)

 - Start deprecating auto module loading based on dev_t (Christoph)

 - bio allocation improvements (Christoph, Chaitanya)

 - Get rid of bio_devname (Christoph)

 - bio clone improvements (Christoph)

 - Block plugging improvements (Christoph)

 - Get rid of genhd.h header (Christoph)

 - Ensure drivers use appropriate flush helpers (Christoph)

 - Refcounting improvements (Christoph)

 - Queue initialization and teardown improvements (Ming, Christoph)

 - Misc fixes/improvements (Barry, Chaitanya, Colin, Dan, Jiapeng,
   Lukas, Nian, Yang, Eric, Chengming)

* tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block: (127 commits)
  block: cancel all throttled bios in del_gendisk()
  block: let blkcg_gq grab request queue's refcnt
  block: avoid use-after-free on throttle data
  block: limit request dispatch loop duration
  block/bfq-iosched: Fix spelling mistake "tenative" -> "tentative"
  sr: simplify the local variable initialization in sr_block_open()
  block: don't merge across cgroup boundaries if blkcg is enabled
  block: fix rq-qos breakage from skipping rq_qos_done_bio()
  block: flush plug based on hardware and software queue order
  block: ensure plug merging checks the correct queue at least once
  block: move rq_qos_exit() into disk_release()
  block: do more work in elevator_exit
  block: move blk_exit_queue into disk_release
  block: move q_usage_counter release into blk_queue_release
  block: don't remove hctx debugfs dir from blk_mq_exit_queue
  block: move blkcg initialization/destroy into disk allocation/release handler
  sr: implement ->free_disk to simplify refcounting
  sd: implement ->free_disk to simplify refcounting
  sd: delay calling free_opal_dev
  sd: call sd_zbc_release_disk before releasing the scsi_device reference
  ...
2022-03-21 16:48:55 -07:00
Christoph Hellwig
28883074fc block: do more work in elevator_exit
Move the calls to ioc_clear_queue and blk_mq_sched_free_rqs into
elevator_exit.  Except for one call where we know we can't have io_cq
structures yet these always go together, and that extra call in an
error path is harmless.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220308055200.735835-14-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-03-08 19:40:01 -07:00
Eric Biggers
f5ec592dd3 block: simplify calling convention of elv_unregister_queue()
Make elv_unregister_queue() a no-op if q->elevator is NULL or is not
registered.

This simplifies the existing callers, as well as the future caller in
the error path of blk_register_queue().

Also don't bother checking whether q is NULL, since it never is.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220124215938.2769-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-28 06:40:23 -07:00
Laibin Qiu
e92bc4cd34 block/wbt: fix negative inflight counter when remove scsi device
Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in
wbt_disable_default() when switch elevator to bfq. And when
we remove scsi device, wbt will be enabled by wbt_enable_default.
If it become false positive between wbt_wait() and wbt_track()
when submit write request.

The following is the scenario that triggered the problem.

T1                          T2                           T3
                            elevator_switch_mq
                            bfq_init_queue
                            wbt_disable_default <= Set
                            rwb->enable_state (OFF)
Submit_bio
blk_mq_make_request
rq_qos_throttle
<= rwb->enable_state (OFF)
                                                         scsi_remove_device
                                                         sd_remove
                                                         del_gendisk
                                                         blk_unregister_queue
                                                         elv_unregister_queue
                                                         wbt_enable_default
                                                         <= Set rwb->enable_state (ON)
q_qos_track
<= rwb->enable_state (ON)
^^^^^^ this request will mark WBT_TRACKED without inflight add and will
lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung.

Fix this by move wbt_enable_default() from elv_unregister to
bfq_exit_queue(). Only re-enable wbt when bfq exit.

Fixes: 76a8040817 ("blk-wbt: make sure throttle is enabled properly")

Remove oneline stale comment, and kill one oneshot local variable.

Signed-off-by: Ming Lei <ming.lei@rehdat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/linux-block/20211214133103.551813-1-qiulaibin@huawei.com/
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-17 07:54:03 -07:00
Ming Lei
672fdcf0e7 block: partition include/linux/blk-cgroup.h
Partition include/linux/blk-cgroup.h into two parts: one is public part,
the other is block layer private part.

Suggested by Christoph Hellwig.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220211101149.2368042-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-11 10:02:41 -07:00
Christoph Hellwig
0c6cb3a293 block: remove the e argument to elevator_exit
All callers pass q->elevator.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211123185312.1432157-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29 06:38:44 -07:00
Christoph Hellwig
f46b81c54b block: remove elevator_exit
Open code elevator_exit in it's only caller, and rename __elevator_exit to
elevator_exit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211123185312.1432157-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29 06:38:44 -07:00
Ming Lei
245a489e81 block: avoid to quiesce queue in elevator_init_mq
elevator_init_mq() is only called before adding disk, when there isn't
any FS I/O, only passthrough requests can be queued, so freezing queue
plus canceling dispatch work is enough to drain any dispatch activities,
then we can avoid synchronize_srcu() in blk_mq_quiesce_queue().

Long boot latency issue can be fixed in case of lots of disks added
during booting.

Fixes: 737eb78e82 ("block: Delay default elevator initialization")
Reported-by: yangerkun <yangerkun@huawei.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211117115502.1600950-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-17 07:43:26 -07:00
John Garry
079a2e3e86 blk-mq: Change shared sbitmap naming to shared tags
Now that shared sbitmap support really means shared tags, rename symbols
to match that.

Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1633429419-228500-15-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-10-18 06:17:03 -06:00
Christoph Hellwig
2e9bc3465a block: move elevator.h to block/
Except for the features passed to blk_queue_required_elevator_features,
elevator.h is only needed internally to the block layer.  Move the
ELEVATOR_F_* definitions to blkdev.h, and the move elevator.h to
block/, dropping all the spurious includes outside of that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-13-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-10-18 06:17:01 -06:00
Ming Lei
866663b7b5 block: return ELEVATOR_DISCARD_MERGE if possible
When merging one bio to request, if they are discard IO and the queue
supports multi-range discard, we need to return ELEVATOR_DISCARD_MERGE
because both block core and related drivers(nvme, virtio-blk) doesn't
handle mixed discard io merge(traditional IO merge together with
discard merge) well.

Fix the issue by returning ELEVATOR_DISCARD_MERGE in this situation,
so both blk-mq and drivers just need to handle multi-range discard.

Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Fixes: 2705dfb209 ("block: fix discard request merge")
Link: https://lore.kernel.org/r/20210729034226.1591070-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-09 14:37:47 -06:00
Christoph Hellwig
d1254a8749 block: remove support for delayed queue registrations
Now that device mapper has been changed to register the disk once
it is fully ready all this code is unused.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-09 11:50:43 -06:00
Bart Van Assche
90b7198001 blk-mq: Introduce the BLK_MQ_F_NO_SCHED_BY_DEFAULT flag
elevator_get_default() uses the following algorithm to select an I/O
scheduler from inside add_disk():
- In case of a single hardware queue or if sharing hardware queues across
  multiple request queues (BLK_MQ_F_TAG_HCTX_SHARED), use mq-deadline.
- Otherwise, use 'none'.

This is a good choice for most but not for all block drivers. Make it
possible to override the selection of mq-deadline with a new flag,
namely BLK_MQ_F_NO_SCHED_BY_DEFAULT.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Martijn Coenen <maco@android.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210805174200.3250718-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-05 11:49:21 -06:00
Jan Kara
fd2ef39cc9 blk: Fix lock inversion between ioc lock and bfqd lock
Lockdep complains about lock inversion between ioc->lock and bfqd->lock:

bfqd -> ioc:
 put_io_context+0x33/0x90 -> ioc->lock grabbed
 blk_mq_free_request+0x51/0x140
 blk_put_request+0xe/0x10
 blk_attempt_req_merge+0x1d/0x30
 elv_attempt_insert_merge+0x56/0xa0
 blk_mq_sched_try_insert_merge+0x4b/0x60
 bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed
 blk_mq_sched_insert_requests+0xd6/0x2b0
 blk_mq_flush_plug_list+0x154/0x280
 blk_finish_plug+0x40/0x60
 ext4_writepages+0x696/0x1320
 do_writepages+0x1c/0x80
 __filemap_fdatawrite_range+0xd7/0x120
 sync_file_range+0xac/0xf0

ioc->bfqd:
 bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed
 put_io_context_active+0x78/0xb0 -> ioc->lock grabbed
 exit_io_context+0x48/0x50
 do_exit+0x7e9/0xdd0
 do_group_exit+0x54/0xc0

To avoid this inversion we change blk_mq_sched_try_insert_merge() to not
free the merged request but rather leave that upto the caller similarly
to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure
to free all the merged requests after dropping bfqd->lock.

Fixes: aee69d78de ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210623093634.27879-3-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-06-24 18:43:55 -06:00
Damien Le Moal
e42cfb1da0 block: Remove unnecessary elevator operation checks
The insert_requests and dispatch_request elevator operations are
mandatory for the correct execution of an elevator, and all implemented
elevators (bfq, kyber and mq-deadline) implement them. As a result,
there is no need to check for these operations before calling them when
a queue has an elevator set. This simplifies the code in
__blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request().

To avoid out-of-tree elevators to crash the kernel in case of bad
implementation, add a check in elv_register() to verify that these
operations are implemented.

A small, probably not significant, IOPS improvement of 0.1% is observed
with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio
runs doing 4K random direct reads with psync and 32 jobs).

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210618015922.713999-1-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-06-18 08:51:48 -06:00
Christoph Hellwig
26a9750aa8 blk-mq: improve the blk_mq_init_allocated_queue interface
Don't return the passed in request_queue but a normal error code, and
drop the elevator_init argument in favor of just calling elevator_init_mq
directly from dm-rq.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-06-11 11:53:02 -06:00