LinuxLists.cc - [bdi_unregister] 165a5e22fa INFO: task swapper:1 blocked for more than 120 seconds.

2017-03-05 02:21:22

Subject: [bdi_unregister] 165a5e22fa INFO: task swapper:1 blocked for more than 120 seconds.

Hi Jan,

FYI next-20170303 is good while mainline is bad with this error.
The attached reproduce-* may help reproduce the issue.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

commit 165a5e22fafb127ecb5914e12e8c32a1f0d3f820
Author: Jan Kara <[email protected]>
AuthorDate: Wed Feb 8 08:05:56 2017 +0100
Commit: Jens Axboe <[email protected]>
CommitDate: Thu Mar 2 16:08:35 2017 -0700

block: Move bdi_unregister() to del_gendisk()

Commit 6cd18e711dd8 "block: destroy bdi before blockdev is
unregistered." moved bdi unregistration (at that time through
bdi_destroy()) from blk_release_queue() to blk_cleanup_queue() because
it needs to happen before blk_unregister_region() call in del_gendisk()
for MD. SCSI though will free up the device number from sd_remove()
called through a maze of callbacks from device_del() in
__scsi_remove_device() before blk_cleanup_queue() and thus similar races
as described in 6cd18e711dd8 can happen for SCSI as well as reported by
Omar [1].

Moving bdi_unregister() to del_gendisk() works for MD and fixes the
problem for SCSI since del_gendisk() gets called from sd_remove() before
freeing the device number.

This also makes device_add_disk() (calling bdi_register_owner()) more
symmetric with del_gendisk().

[1] http://marc.info/?l=linux-block&m=148554717109098&w=2

Tested-by: Lekshmi Pillai <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Tested-by: Omar Sandoval <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

113285b473 blk-mq: ensure that bd->last is always set correctly
165a5e22fa block: Move bdi_unregister() to del_gendisk()
+--------------------------------------------------+------------+------------+
| | 113285b473 | 165a5e22fa |
+--------------------------------------------------+------------+------------+
| boot_successes | 35 | 0 |
| boot_failures | 0 | 15 |
| INFO:task_blocked_for_more_than#seconds | 0 | 15 |
| Kernel_panic-not_syncing:hung_task:blocked_tasks | 0 | 15 |
+--------------------------------------------------+------------+------------+

[ 187.365491] rcu_preempt: wait state: 1 ->state: 0x1
[ 187.366039] rcu_sched: wait state: 1 ->state: 0x1
[ 187.366039] rcu_sched: wait state: 1 ->state: 0x1
[ 187.366564] rcu_bh: wait state: 1 ->state: 0x1
[ 187.366564] rcu_bh: wait state: 1 ->state: 0x1
[ 243.680303] INFO: task swapper:1 blocked for more than 120 seconds.
[ 243.680303] INFO: task swapper:1 blocked for more than 120 seconds.
[ 243.682035] Not tainted 4.10.0-11089-g165a5e2 #2
[ 243.682035] Not tainted 4.10.0-11089-g165a5e2 #2
[ 243.683000] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 243.683000] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 243.684306] swapper D 0 1 0 0x00000000
[ 243.684306] swapper D 0 1 0 0x00000000
[ 243.685246] Call Trace:
[ 243.685246] Call Trace:
[ 243.685650] __schedule+0x31a/0xc00
[ 243.685650] __schedule+0x31a/0xc00
[ 243.686236] schedule+0x7b/0x170
[ 243.686236] schedule+0x7b/0x170
[ 243.686803] bdi_unregister+0x3a3/0x430
[ 243.686803] bdi_unregister+0x3a3/0x430
[ 243.687447] ? woken_wake_function+0x40/0x40
[ 243.687447] ? woken_wake_function+0x40/0x40
[ 243.688150] del_gendisk+0x232/0x370
[ 243.688150] del_gendisk+0x232/0x370
[ 243.688721] sd_remove+0x97/0x140
[ 243.688721] sd_remove+0x97/0x140
[ 243.689260] device_release_driver_internal+0x4b8/0x4d0
[ 243.689260] device_release_driver_internal+0x4b8/0x4d0
[ 243.690065] device_release_driver+0x1a/0x30
[ 243.690065] device_release_driver+0x1a/0x30
[ 243.690928] bus_remove_device+0x15a/0x1f0
[ 243.690928] bus_remove_device+0x15a/0x1f0
[ 243.691558] device_del+0x34d/0x5a0
[ 243.691558] device_del+0x34d/0x5a0
[ 243.692155] ? kobject_put+0xf6/0x1d0
[ 243.692155] ? kobject_put+0xf6/0x1d0
[ 243.692700] __scsi_remove_device+0x1a3/0x1c0
[ 243.692700] __scsi_remove_device+0x1a3/0x1c0
[ 243.693665] scsi_forget_host+0xb7/0x120
[ 243.693665] scsi_forget_host+0xb7/0x120
[ 243.694301] scsi_remove_host+0xf1/0x300
[ 243.694301] scsi_remove_host+0xf1/0x300
[ 243.694973] sdebug_driver_remove+0x34/0x120
[ 243.694973] sdebug_driver_remove+0x34/0x120
[ 243.695621] ? devices_kset_move_last+0x9d/0x100
[ 243.695621] ? devices_kset_move_last+0x9d/0x100
[ 243.696430] driver_probe_device+0x172/0x6b0
[ 243.696430] driver_probe_device+0x172/0x6b0
[ 243.697413] __device_attach_driver+0x15d/0x1d0
[ 243.697413] __device_attach_driver+0x15d/0x1d0
[ 243.698460] ? __driver_attach+0x1b0/0x1b0
[ 243.698460] ? __driver_attach+0x1b0/0x1b0
[ 243.699111] bus_for_each_drv+0xb1/0x110
[ 243.699111] bus_for_each_drv+0xb1/0x110
[ 243.699856] __device_attach+0x14d/0x210
[ 243.699856] __device_attach+0x14d/0x210
[ 243.700643] ? __driver_attach+0x1b0/0x1b0
[ 243.700643] ? __driver_attach+0x1b0/0x1b0
[ 243.701362] device_initial_probe+0x1b/0x30
[ 243.701362] device_initial_probe+0x1b/0x30
[ 243.701886] bus_probe_device+0xe5/0x100
[ 243.701886] bus_probe_device+0xe5/0x100
[ 243.702447] device_add+0x822/0xc20
[ 243.702447] device_add+0x822/0xc20
[ 243.702879] ? pm_runtime_init+0x125/0x140
[ 243.702879] ? pm_runtime_init+0x125/0x140
[ 243.703366] device_register+0x2e/0x40
[ 243.703366] device_register+0x2e/0x40
[ 243.703823] sdebug_add_adapter+0x144/0x2e0
[ 243.703823] sdebug_add_adapter+0x144/0x2e0
[ 243.704381] ? kobject_uevent+0x18/0x30
[ 243.704381] ? kobject_uevent+0x18/0x30
[ 243.704881] scsi_debug_init+0x955/0xb9d
[ 243.704881] scsi_debug_init+0x955/0xb9d
[ 243.705372] ? init_sg+0x1a9/0x212
[ 243.705372] ? init_sg+0x1a9/0x212
[ 243.705763] ? init_sg+0x212/0x212
[ 243.705763] ? init_sg+0x212/0x212
[ 243.706166] do_one_initcall+0x5d/0x2b0
[ 243.706166] do_one_initcall+0x5d/0x2b0
[ 243.706634] ? parse_args+0x44e/0x710
[ 243.706634] ? parse_args+0x44e/0x710
[ 243.707059] ? kernel_init_freeable+0x20b/0x3ab
[ 243.707059] ? kernel_init_freeable+0x20b/0x3ab
[ 243.707569] kernel_init_freeable+0x23c/0x3ab
[ 243.707569] kernel_init_freeable+0x23c/0x3ab
[ 243.708076] ? rest_init+0x270/0x270
[ 243.708076] ? rest_init+0x270/0x270
[ 243.708543] kernel_init+0x16/0x250
[ 243.708543] kernel_init+0x16/0x250
[ 243.708978] ret_from_fork+0x21/0x30
[ 243.708978] ret_from_fork+0x21/0x30
[ 243.709399]
[ 243.709399] Showing all locks held in the system:
[ 243.709399]
[ 243.709399] Showing all locks held in the system:
[ 243.710265] 3 locks held by swapper/1:
[ 243.710265] 3 locks held by swapper/1:
[ 243.710785] #0: (&dev->mutex){......}, at: [<987efeb8>] __device_attach+0x28/0x210
[ 243.710785] #0: (&dev->mutex){......}, at: [<987efeb8>] __device_attach+0x28/0x210
[ 243.711670] #1: (&shost->scan_mutex){+.+.+.}, at: [<9883cac1>] scsi_remove_host+0x21/0x300
[ 243.711670] #1: (&shost->scan_mutex){+.+.+.}, at: [<9883cac1>] scsi_remove_host+0x21/0x300
[ 243.712674] #2: (&dev->mutex){......}, at: [<987f0d94>] device_release_driver_internal+0x54/0x4d0
[ 243.712674] #2: (&dev->mutex){......}, at: [<987f0d94>] device_release_driver_internal+0x54/0x4d0
[ 243.713807] 2 locks held by khungtaskd/13:
[ 243.713807] 2 locks held by khungtaskd/13:
[ 243.714297] #0: (rcu_read_lock){......}, at: [<97f5f626>] watchdog+0x126/0x8c0
[ 243.714297] #0: (rcu_read_lock){......}, at: [<97f5f626>] watchdog+0x126/0x8c0
[ 243.715168] #1: (tasklist_lock){.+.+..}, at: [<97ee6d62>] debug_show_all_locks+0x52/0x320
[ 243.715168] #1: (tasklist_lock){.+.+..}, at: [<97ee6d62>] debug_show_all_locks+0x52/0x320
[ 243.716128]
[ 243.716128]
[ 243.716372] =============================================
[ 243.716372]
[ 243.716372] =============================================
[ 243.716372]
[ 243.717191] Kernel panic - not syncing: hung_task: blocked tasks
[ 243.717191] Kernel panic - not syncing: hung_task: blocked tasks
[ 243.717889] CPU: 0 PID: 13 Comm: khungtaskd Not tainted 4.10.0-11089-g165a5e2 #2
[ 243.717889] CPU: 0 PID: 13 Comm: khungtaskd Not tainted 4.10.0-11089-g165a5e2 #2
[ 243.718742] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[ 243.718742] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[ 243.719871] Call Trace:
[ 243.719871] Call Trace:
[ 243.720185] dump_stack+0x32/0x43
[ 243.720185] dump_stack+0x32/0x43
[ 243.720185] panic+0x135/0x408
[ 243.720185] panic+0x135/0x408
[ 243.720185] watchdog+0x6d3/0x8c0
[ 243.720185] watchdog+0x6d3/0x8c0
[ 243.720185] kthread+0x151/0x1d0
[ 243.720185] kthread+0x151/0x1d0
[ 243.720185] ? hung_task_panic+0x20/0x20
[ 243.720185] ? hung_task_panic+0x20/0x20
[ 243.720185] ? kthread_worker_fn+0x220/0x220
[ 243.720185] ? kthread_worker_fn+0x220/0x220
[ 243.720185] ret_from_fork+0x21/0x30
[ 243.720185] ret_from_fork+0x21/0x30
[ 243.720185] Kernel Offset: 0x16e00000 from 0x81000000 (relocation range: 0x80000000-0xa07dffff)
[ 243.720185] Kernel Offset: 0x16e00000 from 0x81000000 (relocation range: 0x80000000-0xa07dffff)

# HH:MM RESULT GOOD BAD GOOD_BUT_DIRTY DIRTY_NOT_BAD
git bisect start 0724f5d8ca3a89134a8c248aa4c311ce43d53512 c470abd4fde40ea6a0846a2beab642a578c0b8cd --
git bisect bad 304f9c7ff9aabc9a3cec12bf88f29d24139ac370 # 14:12 B 0 4 15 0 Merge 'linux-review/Roger-Quadros/Revert-usb-gadget-uvc-Add-missing-call-for-additional-setup-data/20170303-232925' into devel-spot-201703040603
git bisect bad a28ca518ffc36daf89550978066ad20094c19e51 # 14:33 B 0 8 22 3 Merge 'linux-review/Arushi-Singhal/staging-speakup-Alignment-match-open-parenthesis/20170304-030809' into devel-spot-201703040603
git bisect bad 93354ede964ded2791d3b573635d538b14590545 # 14:55 B 0 4 15 0 Merge 'linux-review/Georgios-Emmanouil/Staging-wilc1000-wilc_sdio-Modified-comment-style-to-preferred-kernel-comment-style/20170304-050826' into devel-spot-201703040603
git bisect bad 402decdec94a2e4e2635ef662e57f6217a305d81 # 15:36 B 0 11 22 0 Merge 'linux-review/Heiner-Kallweit/staging-fbtft-improve-a-syslog-message-in-fbtft_register_framebuffer/20170304-054107' into devel-spot-201703040603
git bisect bad 1735b51c4dda1ca7f2c239c4b790c3c638281f54 # 15:53 B 0 6 17 0 Merge 'block/for-linus' into devel-spot-201703040603
git bisect good cf5f16969d36dfa64e92cf19594b94de0c381519 # 16:05 G 11 0 0 0 0day base guard for 'devel-spot-201703040603'
git bisect good caa59428971d5ad81d19512365c9ba580d83268c # 16:23 G 11 0 0 0 Merge tag 'staging-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
git bisect good d5500a074741b78b7f778b4ab3415d5ecdcda0a7 # 16:48 G 11 0 0 0 Merge tag 'usercopy-v4.11-rc1.fix' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
git bisect good 7067739df23ffd641ca99c967830e0ed2ba39eab # 17:13 G 11 0 0 0 Merge branch 'i2c/for-4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
git bisect good b2deee2dc06db7cdf99b84346e69bdb9db9baa85 # 17:47 G 11 0 0 0 Merge tag 'ceph-for-4.11-rc1' of git://github.com/ceph/ceph-client
git bisect good 010426079ec1228a7f980d2eef766a84c0f9241a # 18:03 G 11 0 0 0 sched/headers: Prepare for new header dependencies before moving more code to <linux/sched/mm.h>
git bisect good 3f80dd67c367878aaad16e458eebc3c8980bb841 # 18:28 G 11 0 0 0 Merge tag 'acpi-extra-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
git bisect good e26512fea5bcd6602dbf02a551ed073cd4529449 # 18:42 G 10 0 0 0 sched/headers: Remove <linux/cred.h> inclusion from <linux/sched.h>
git bisect good 78769912f680fc0a79a67e798a0ae76f07e63a7b # 19:08 G 11 0 0 0 Merge tag 'linux-kselftest-4.11-rc1-urgent_fix' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest
git bisect good 1827adb11ad26b2290dc9fe2aaf54976b2439865 # 19:21 G 11 0 0 0 Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect bad 165a5e22fafb127ecb5914e12e8c32a1f0d3f820 # 19:39 B 0 11 22 0 block: Move bdi_unregister() to del_gendisk()
git bisect good 6a8a21546507a3ec88e81c2ec927a3fb63efa8ff # 19:55 G 11 0 0 0 nbd: stop leaking sockets
git bisect good e02898b423802b1f3a3aaa7f16e896da069ba8f7 # 20:36 G 11 0 0 0 loop: fix LO_FLAGS_PARTSCAN hang
git bisect good 7b36a7189fc320f0b783dd51bd1f541db56cfbdd # 20:53 G 11 0 0 0 block: don't call ioc_exit_icq() with the queue lock held for blk-mq
git bisect good 113285b473824922498d07d7f82459507b9792eb # 21:37 G 11 0 0 0 blk-mq: ensure that bd->last is always set correctly
# first bad commit: [165a5e22fafb127ecb5914e12e8c32a1f0d3f820] block: Move bdi_unregister() to del_gendisk()
git bisect good 113285b473824922498d07d7f82459507b9792eb # 21:41 G 31 0 0 0 blk-mq: ensure that bd->last is always set correctly
# extra tests with CONFIG_DEBUG_INFO_REDUCED
git bisect bad 165a5e22fafb127ecb5914e12e8c32a1f0d3f820 # 22:16 B 0 10 22 1 block: Move bdi_unregister() to del_gendisk()
# extra tests on HEAD of linux-devel/devel-spot-201703040603
git bisect bad 0724f5d8ca3a89134a8c248aa4c311ce43d53512 # 22:16 B 0 39 55 2 0day head guard for 'devel-spot-201703040603'
# extra tests on tree/branch linus/master
git bisect bad 0710f3ff91ecc4a715db6e4d0690472b13c4dac6 # 22:42 B 0 7 18 0 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
# extra tests with first bad commit reverted
git bisect good 8b222187187cd9372d0d1ee036f1966e142bbd42 # 23:09 G 10 0 0 0 Revert "block: Move bdi_unregister() to del_gendisk()"
# extra tests on tree/branch linux-next/master
git bisect good c0b7b2b33bd17f7155956d0338ce92615da686c9 # 23:28 G 11 0 0 0 Add linux-next specific files for 20170303

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2017-03-05 02:24:10

On Tue 07-03-17 17:26:56, Jan Kara wrote:
> On Tue 07-03-17 08:10:29, James Bottomley wrote:
> > On Tue, 2017-03-07 at 15:41 +0100, Jan Kara wrote:
> > > On Mon 06-03-17 09:25:42, James Bottomley wrote:
> > > > On Mon, 2017-03-06 at 17:13 +0100, Jan Kara wrote:
> > > > > On Mon 06-03-17 07:44:55, James Bottomley wrote:
> > > ...
> > > > > > > Sure. The call trace is:
> > > > > > >
> > > > > > > [ 41.919244] ------------[ cut here ]------------
> > > > > > > [ 41.919263] WARNING: CPU: 4 PID: 2335 at
> > > > > > > drivers/scsi/sd.c:3332
> > > > > > > sd_shutdown+0x2f/0x100
> > > > > > > [ 41.919268] Modules linked in: scsi_debug(+) netconsole
> > > > > > > loop btrfs raid6_pq zlib_deflate lzo_compress xor
> > > > > > > [ 41.919319] CPU: 4 PID: 2335 Comm: modprobe Not tainted
> > > > > > > 4.11.0-rc1-xen+ #49
> > > > > > > [ 41.919325] Hardware name: Bochs Bochs, BIOS Bochs
> > > > > > > 01/01/2011
> > > > > > > [ 41.919331] Call Trace:
> > > > > > > [ 41.919343] dump_stack+0x8e/0xf0
> > > > > > > [ 41.919354] __warn+0x116/0x120
> > > > > > > [ 41.919361] warn_slowpath_null+0x1d/0x20
> > > > > > > [ 41.919368] sd_shutdown+0x2f/0x100
> > > > > > > [ 41.919374] sd_remove+0x70/0xd0
> > > > > > >
> > > > > > > *** Here is the unexpected step I guess...
> > > > > > >
> > > > > > > [ 41.919383] driver_probe_device+0xe0/0x4c0
> > > > > >
> > > > > > Exactly. It's this, I think
> > > > > >
> > > > > > bool test_remove =
> > > > > > IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE)
> > > > > > &&
> > > > > > !drv->suppress_bind_attrs;
> > > > > >
> > > > > > You have that config option set.
> > > > >
> > > > > Yes - or better said 0-day testing has it set. Maybe that is not
> > > > > a sane default for 0-day tests? The option is explicitely marked
> > > > > as "unstable"... Fengguang?
> > > > >
> > > > > > So the drivers base layer is calling ->remove after probe and
> > > > > > triggering the destruction of the queue.
> > > > > >
> > > > > > What to do about this (apart from nuke such a stupid option) is
> > > > > > somewhat more problematic.
> > > > >
> > > > > I guess this is between you and Greg :).
> > > >
> > > > Nice try, sport ... you qualify just behind Dan in the "not my
> > > > problem" olympic hurdles event. I'm annoyed because there's no
> > > > indication in the log that the driver add behaviour is radically
> > > > altered, so I've been staring at the wrong code for weeks.
> > > > However, the unbind/rebind should work, so the real issue is that
> > > > your bdi changes (or perhaps something else in block) have induced
> > > > a regression in the unbinding of upper layer drivers. If you're
> > > > going to release the bdi in del_gendisk, you have to have some
> > > > mechanism for re-acquiring it on re-probe (likely with the same
> > > > name) otherwise rebind is broken for every block driver.
> > >
> > > So my patch does not release bdi in del_gendisk(). Bdi has two
> > > initialization / destruction phases (similarly to request queue). You
> > > allocate and initialize bdi through bdi_init(), then you call
> > > bdi_register() to register it (which happens in device_add_disk()).
> > > On shutdown you have to first call bdi_unregister() (used to be
> > > called from blk_cleanup_queue(), my patch moved it to del_gendisk()).
> > > After that the last reference to bdi may be dropped which does final
> > > bdi destruction.
> > >
> > > So do I understand correctly that SCSI may call device_add_disk(),
> > > del_gendisk() repeatedly for the same request queue?
> >
> > Yes. The upper drivers (sd, sr, st and sg) follow a device model.
> > They can thus be bound and unbound many times during the lifetime of a
> > SCSI device.
> >
> > > If yes, then indeed I have a bug to fix... But gendisk seems to get
> > > allocated from scratch on each probe so we don't call
> > > device_add_disk(), del_gendisk() more times on the same disk, right?
> >
> > Right, gendisk, being a generic representation of a disk is a property
> > of the upper layer drivers. We actually cheat and use it in all of
> > them (including the apparent character ones, they use alloc_disk,
> > put_disk but not add_disk). So it has to be freed when the driver is
> > unbound and reallocated when it is bound. It's the fundamental entity
> > which embeds the SCSI upper layer driver lifetime.
> >
> > > > The fact that the second rebind tried with a different name
> > > > indicates that sd_devt_release wasn't called, so some vestige of
> > > > the devt remains on the subsequent rebind.
> > >
> > > Yep, I guess that's caused by Dan's patch (commit 0dba1314d4f8 now)
> > > which calls put_disk_devt() only in blk_cleanup_queue() which, if I
> > > understood you correctly, does not get called during unbind-bind
> > > cycle? In fact Dan's patch would end up leaking devt's because of
> > > repeated device_add_disk() calls for the same request queue...
> >
> > That's a bit unfortunate.
> >
> > > > Here's the problem: the queue belongs to SCSI (the lower layer), so
> > > > it's not going to change because it doesn't see the release. The
> > > > gendisk and its allied stuff belongs to sd so it gets freed and re
> > > > -created for the same queue. Something in block is very confused
> > > > when this happens.
> > >
> > > Yep, I think the binding of request queue to different gendisks is
> > > something I or Dan did not expect.
> >
> > OK, so I think we now understand why this is happening ... the question
> > is what we do about it? Is it fixable or do we need to go back to
> > basics? The fundamental property which got broken by these patches is
> > the idea of the separation of the lifecycles of the queue and the
> > gendisk. The only requirement is that the queue must exist before the
> > gendisk is created and must be destroyed after it. This doesn't forbid
> > there being many gendisk lifetimes over one queue lifetime and this is
> > what we rely on for the SCSI driver model. We rarely get called on it
> > because unbind/rebind of a ULD is rarely done in production (it's
> > mostly a devtest thing).
>
> For now I think it's fixable. Let's see what I'll be able to come up with.
> Let me also note that before my patch moving bdi_unregister() to
> del_gendisk() (commit 165a5e22fafb), the SCSI driver model was buggy in a
> different way - because bdi_unregister() was called only from
> blk_cleanup_queue(), we were leaking bdi->owner reference to gendisk by
> repeated calls to bdi_register_owner() from device_add_disk() and
> thus gendisks were never freed after unbind/bind (I've actually verified
> this bug exists with debug messages). Also as a result request queue use
> count was steadily increasing with each new gendisk and request queue could
> never get freed after unbind / rebind.
>
> My patch silently fixed this leakage but introduced a different set of
> problems which I'll try to fix.

Attached patch fixes the problem for me. If I also revert commit
0dba1314d4f81115dce711292ec7981d17231064 "scsi, block: fix duplicate bdi
name registration crashes" which is not needed with my
165a5e22fafb127ecb5914e12e8c32a1f0d3f820 "block: Move bdi_unregister() to
del_gendisk()", the device names also do not get incremented and I end up
with 'sda' device (otherwise I end up with sdc).

Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR

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