kernel/linux.git/drivers/md/md.c, branch linux-4.4.y

md: md_open returns -EBUSY when entering racing area

2021-05-22T08:38:21+00:00

commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream. commit d3374825ce57 ("md: make devices disappear when they are no longer needed.") introduced protection between mddev creating & removing. The md_open shouldn't create mddev when all_mddevs list doesn't contain mddev. With currently code logic, there will be very easy to trigger soft lockup in non-preempt env. This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which will break the infinitely retry when md_open enter racing area. This patch is partly fix soft lockup issue, full fix needs mddev_find is split into two functions: mddev_find & mddev_find_or_alloc. And md_open should call new mddev_find (it only does searching job). For more detail, please refer with Christoph's "split mddev_find" patch in later commits. *** env *** kvm-qemu VM 2C1G with 2 iscsi luns kernel should be non-preempt *** script *** about trigger every time with below script ``` 1 node1="mdcluster1" 2 node2="mdcluster2" 3 4 mdadm -Ss 5 ssh ${node2} "mdadm -Ss" 6 wipefs -a /dev/sda /dev/sdb 7 mdadm -CR /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda \ /dev/sdb --assume-clean 8 9 for i in {1..10}; do 10 echo ==== $i ====; 11 12 echo "test ...." 13 ssh ${node2} "mdadm -A /dev/md0 /dev/sda /dev/sdb" 14 sleep 1 15 16 echo "clean ....." 17 ssh ${node2} "mdadm -Ss" 18 done ``` I use mdcluster env to trigger soft lockup, but it isn't mdcluster speical bug. To stop md array in mdcluster env will do more jobs than non-cluster array, which will leave enough time/gap to allow kernel to run md_open. *** stack *** ``` [ 884.226509] mddev_put+0x1c/0xe0 [md_mod] [ 884.226515] md_open+0x3c/0xe0 [md_mod] [ 884.226518] __blkdev_get+0x30d/0x710 [ 884.226520] ? bd_acquire+0xd0/0xd0 [ 884.226522] blkdev_get+0x14/0x30 [ 884.226524] do_dentry_open+0x204/0x3a0 [ 884.226531] path_openat+0x2fc/0x1520 [ 884.226534] ? seq_printf+0x4e/0x70 [ 884.226536] do_filp_open+0x9b/0x110 [ 884.226542] ? md_release+0x20/0x20 [md_mod] [ 884.226543] ? seq_read+0x1d8/0x3e0 [ 884.226545] ? kmem_cache_alloc+0x18a/0x270 [ 884.226547] ? do_sys_open+0x1bd/0x260 [ 884.226548] do_sys_open+0x1bd/0x260 [ 884.226551] do_syscall_64+0x5b/0x1e0 [ 884.226554] entry_SYSCALL_64_after_hwframe+0x44/0xa9 ``` *** rootcause *** "mdadm -A" (or other array assemble commands) will start a daemon "mdadm --monitor" by default. When "mdadm -Ss" is running, the stop action will wakeup "mdadm --monitor". The "--monitor" daemon will immediately get info from /proc/mdstat. This time mddev in kernel still exist, so /proc/mdstat still show md device, which makes "mdadm --monitor" to open /dev/md0. The previously "mdadm -Ss" is removing action, the "mdadm --monitor" open action will trigger md_open which is creating action. Racing is happening. ``` : "mdadm -Ss" md_release mddev_put deletes mddev from all_mddevs queue_work for mddev_delayed_delete at this time, "/dev/md0" is still available for opening : "mdadm --monitor ..." md_open + mddev_find can't find mddev of /dev/md0, and create a new mddev and | return. + trigger "if (mddev->gendisk != bdev->bd_disk)" and return -ERESTARTSYS. ``` In non-preempt kernel, is occupying on current CPU. and mddev_delayed_delete which was created in also can't be schedule. In preempt kernel, it can also trigger above racing. But kernel doesn't allow one thread running on a CPU all the time. after running some time, the later "mdadm -A" (refer above script line 13) will call md_alloc to alloc a new gendisk for mddev. it will break md_open statement "if (mddev->gendisk != bdev->bd_disk)" and return 0 to caller, the soft lockup is broken. Cc: stable@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Zhao Heming Signed-off-by: Song Liu Signed-off-by: Greg Kroah-Hartman

md: factor out a mddev_find_locked helper from mddev_find

2021-05-22T08:38:21+00:00

commit 8b57251f9a91f5e5a599de7549915d2d226cc3af upstream. Factor out a self-contained helper to just lookup a mddev by the dev_t "unit". Cc: stable@vger.kernel.org Reviewed-by: Heming Zhao Signed-off-by: Christoph Hellwig Signed-off-by: Song Liu Signed-off-by: Greg Kroah-Hartman

md: don't flush workqueue unconditionally in md_open

2020-06-20T08:23:21+00:00

[ Upstream commit f6766ff6afff70e2aaf39e1511e16d471de7c3ae ] We need to check mddev->del_work before flush workqueu since the purpose of flush is to ensure the previous md is disappeared. Otherwise the similar deadlock appeared if LOCKDEP is enabled, it is due to md_open holds the bdev->bd_mutex before flush workqueue. kernel: [ 154.522645] ====================================================== kernel: [ 154.522647] WARNING: possible circular locking dependency detected kernel: [ 154.522650] 5.6.0-rc7-lp151.27-default #25 Tainted: G O kernel: [ 154.522651] ------------------------------------------------------ kernel: [ 154.522653] mdadm/2482 is trying to acquire lock: kernel: [ 154.522655] ffff888078529128 ((wq_completion)md_misc){+.+.}, at: flush_workqueue+0x84/0x4b0 kernel: [ 154.522673] kernel: [ 154.522673] but task is already holding lock: kernel: [ 154.522675] ffff88804efa9338 (&bdev->bd_mutex){+.+.}, at: __blkdev_get+0x79/0x590 kernel: [ 154.522691] kernel: [ 154.522691] which lock already depends on the new lock. kernel: [ 154.522691] kernel: [ 154.522694] kernel: [ 154.522694] the existing dependency chain (in reverse order) is: kernel: [ 154.522696] kernel: [ 154.522696] -> #4 (&bdev->bd_mutex){+.+.}: kernel: [ 154.522704] __mutex_lock+0x87/0x950 kernel: [ 154.522706] __blkdev_get+0x79/0x590 kernel: [ 154.522708] blkdev_get+0x65/0x140 kernel: [ 154.522709] blkdev_get_by_dev+0x2f/0x40 kernel: [ 154.522716] lock_rdev+0x3d/0x90 [md_mod] kernel: [ 154.522719] md_import_device+0xd6/0x1b0 [md_mod] kernel: [ 154.522723] new_dev_store+0x15e/0x210 [md_mod] kernel: [ 154.522728] md_attr_store+0x7a/0xc0 [md_mod] kernel: [ 154.522732] kernfs_fop_write+0x117/0x1b0 kernel: [ 154.522735] vfs_write+0xad/0x1a0 kernel: [ 154.522737] ksys_write+0xa4/0xe0 kernel: [ 154.522745] do_syscall_64+0x64/0x2b0 kernel: [ 154.522748] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522749] kernel: [ 154.522749] -> #3 (&mddev->reconfig_mutex){+.+.}: kernel: [ 154.522752] __mutex_lock+0x87/0x950 kernel: [ 154.522756] new_dev_store+0xc9/0x210 [md_mod] kernel: [ 154.522759] md_attr_store+0x7a/0xc0 [md_mod] kernel: [ 154.522761] kernfs_fop_write+0x117/0x1b0 kernel: [ 154.522763] vfs_write+0xad/0x1a0 kernel: [ 154.522765] ksys_write+0xa4/0xe0 kernel: [ 154.522767] do_syscall_64+0x64/0x2b0 kernel: [ 154.522769] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522770] kernel: [ 154.522770] -> #2 (kn->count#253){++++}: kernel: [ 154.522775] __kernfs_remove+0x253/0x2c0 kernel: [ 154.522778] kernfs_remove+0x1f/0x30 kernel: [ 154.522780] kobject_del+0x28/0x60 kernel: [ 154.522783] mddev_delayed_delete+0x24/0x30 [md_mod] kernel: [ 154.522786] process_one_work+0x2a7/0x5f0 kernel: [ 154.522788] worker_thread+0x2d/0x3d0 kernel: [ 154.522793] kthread+0x117/0x130 kernel: [ 154.522795] ret_from_fork+0x3a/0x50 kernel: [ 154.522796] kernel: [ 154.522796] -> #1 ((work_completion)(&mddev->del_work)){+.+.}: kernel: [ 154.522800] process_one_work+0x27e/0x5f0 kernel: [ 154.522802] worker_thread+0x2d/0x3d0 kernel: [ 154.522804] kthread+0x117/0x130 kernel: [ 154.522806] ret_from_fork+0x3a/0x50 kernel: [ 154.522807] kernel: [ 154.522807] -> #0 ((wq_completion)md_misc){+.+.}: kernel: [ 154.522813] __lock_acquire+0x1392/0x1690 kernel: [ 154.522816] lock_acquire+0xb4/0x1a0 kernel: [ 154.522818] flush_workqueue+0xab/0x4b0 kernel: [ 154.522821] md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522823] __blkdev_get+0xea/0x590 kernel: [ 154.522825] blkdev_get+0x65/0x140 kernel: [ 154.522828] do_dentry_open+0x1d1/0x380 kernel: [ 154.522831] path_openat+0x567/0xcc0 kernel: [ 154.522834] do_filp_open+0x9b/0x110 kernel: [ 154.522836] do_sys_openat2+0x201/0x2a0 kernel: [ 154.522838] do_sys_open+0x57/0x80 kernel: [ 154.522840] do_syscall_64+0x64/0x2b0 kernel: [ 154.522842] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522844] kernel: [ 154.522844] other info that might help us debug this: kernel: [ 154.522844] kernel: [ 154.522846] Chain exists of: kernel: [ 154.522846] (wq_completion)md_misc --> &mddev->reconfig_mutex --> &bdev->bd_mutex kernel: [ 154.522846] kernel: [ 154.522850] Possible unsafe locking scenario: kernel: [ 154.522850] kernel: [ 154.522852] CPU0 CPU1 kernel: [ 154.522853] ---- ---- kernel: [ 154.522854] lock(&bdev->bd_mutex); kernel: [ 154.522856] lock(&mddev->reconfig_mutex); kernel: [ 154.522858] lock(&bdev->bd_mutex); kernel: [ 154.522860] lock((wq_completion)md_misc); kernel: [ 154.522861] kernel: [ 154.522861] *** DEADLOCK *** kernel: [ 154.522861] kernel: [ 154.522864] 1 lock held by mdadm/2482: kernel: [ 154.522865] #0: ffff88804efa9338 (&bdev->bd_mutex){+.+.}, at: __blkdev_get+0x79/0x590 kernel: [ 154.522868] kernel: [ 154.522868] stack backtrace: kernel: [ 154.522873] CPU: 1 PID: 2482 Comm: mdadm Tainted: G O 5.6.0-rc7-lp151.27-default #25 kernel: [ 154.522875] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 kernel: [ 154.522878] Call Trace: kernel: [ 154.522881] dump_stack+0x8f/0xcb kernel: [ 154.522884] check_noncircular+0x194/0x1b0 kernel: [ 154.522888] ? __lock_acquire+0x1392/0x1690 kernel: [ 154.522890] __lock_acquire+0x1392/0x1690 kernel: [ 154.522893] lock_acquire+0xb4/0x1a0 kernel: [ 154.522895] ? flush_workqueue+0x84/0x4b0 kernel: [ 154.522898] flush_workqueue+0xab/0x4b0 kernel: [ 154.522900] ? flush_workqueue+0x84/0x4b0 kernel: [ 154.522905] ? md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522908] md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522910] __blkdev_get+0xea/0x590 kernel: [ 154.522912] ? bd_acquire+0xc0/0xc0 kernel: [ 154.522914] blkdev_get+0x65/0x140 kernel: [ 154.522916] ? bd_acquire+0xc0/0xc0 kernel: [ 154.522918] do_dentry_open+0x1d1/0x380 kernel: [ 154.522921] path_openat+0x567/0xcc0 kernel: [ 154.522923] ? __lock_acquire+0x380/0x1690 kernel: [ 154.522926] do_filp_open+0x9b/0x110 kernel: [ 154.522929] ? __alloc_fd+0xe5/0x1f0 kernel: [ 154.522935] ? kmem_cache_alloc+0x28c/0x630 kernel: [ 154.522939] ? do_sys_openat2+0x201/0x2a0 kernel: [ 154.522941] do_sys_openat2+0x201/0x2a0 kernel: [ 154.522944] do_sys_open+0x57/0x80 kernel: [ 154.522946] do_syscall_64+0x64/0x2b0 kernel: [ 154.522948] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522951] RIP: 0033:0x7f98d279d9ae And md_alloc also flushed the same workqueue, but the thing is different here. Because all the paths call md_alloc don't hold bdev->bd_mutex, and the flush is necessary to avoid race condition, so leave it as it is. Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu Signed-off-by: Sasha Levin

md: don't set In_sync if array is frozen

2019-10-05T10:27:47+00:00

[ Upstream commit 062f5b2ae12a153644c765e7ba3b0f825427be1d ] When a disk is added to array, the following path is called in mdadm. Manage_subdevs -> sysfs_freeze_array -> Manage_add -> sysfs_set_str(&info, NULL, "sync_action","idle") Then from kernel side, Manage_add invokes the path (add_new_disk -> validate_super = super_1_validate) to set In_sync flag. Since In_sync means "device is in_sync with rest of array", and the new added disk need to resync thread to help the synchronization of data. And md_reap_sync_thread would call spare_active to set In_sync for the new added disk finally. So don't set In_sync if array is in frozen. Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu Signed-off-by: Sasha Levin

md: don't call spare_active in md_reap_sync_thread if all member devices can't work

2019-10-05T10:27:47+00:00

[ Upstream commit 0d8ed0e9bf9643f27f4816dca61081784dedb38d ] When add one disk to array, the md_reap_sync_thread is responsible to activate the spare and set In_sync flag for the new member in spare_active(). But if raid1 has one member disk A, and disk B is added to the array. Then we offline A before all the datas are synchronized from A to B, obviously B doesn't have the latest data as A, but B is still marked with In_sync flag. So let's not call spare_active under the condition, otherwise B is still showed with 'U' state which is not correct. Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu Signed-off-by: Sasha Levin

md: fix for divide error in status_resync

2019-07-21T07:07:08+00:00

[ Upstream commit 9642fa73d073527b0cbc337cc17a47d545d82cd2 ] Stopping external metadata arrays during resync/recovery causes retries, loop of interrupting and starting reconstruction, until it hit at good moment to stop completely. While these retries curr_mark_cnt can be small- especially on HDD drives, so subtraction result can be smaller than 0. However it is casted to uint without checking. As a result of it the status bar in /proc/mdstat while stopping is strange (it jumps between 0% and 99%). The real problem occurs here after commit 72deb455b5ec ("block: remove CONFIG_LBDAF"). Sector_div() macro has been changed, now the divisor is casted to uint32. For db = -8 the divisior(db/32-1) becomes 0. Check if db value can be really counted and replace these macro by div64_u64() inline. Signed-off-by: Mariusz Tkaczyk Signed-off-by: Song Liu Signed-off-by: Sasha Levin

md: add mddev->pers to avoid potential NULL pointer dereference

2019-06-11T10:23:44+00:00

commit ee37e62191a59d253fc916b9fc763deb777211e2 upstream. When doing re-add, we need to ensure rdev->mddev->pers is not NULL, which can avoid potential NULL pointer derefence in fallowing add_bound_rdev(). Fixes: a6da4ef85cef ("md: re-add a failed disk") Cc: Xiao Ni Cc: NeilBrown Cc: # 4.4+ Reviewed-by: NeilBrown Signed-off-by: Yufen Yu Signed-off-by: Song Liu Signed-off-by: Greg Kroah-Hartman

MD: fix invalid stored role for a disk - try2

2018-11-21T08:27:38+00:00

commit 9e753ba9b9b405e3902d9f08aec5f2ea58a0c317 upstream. Commit d595567dc4f0 (MD: fix invalid stored role for a disk) broke linear hotadd. Let's only fix the role for disks in raid1/10. Based on Guoqing's original patch. Reported-by: kernel test robot Cc: Gioh Kim Cc: Guoqing Jiang Signed-off-by: Shaohua Li Signed-off-by: Greg Kroah-Hartman

MD: fix invalid stored role for a disk

2018-11-21T08:27:33+00:00

[ Upstream commit d595567dc4f0c1d90685ec1e2e296e2cad2643ac ] If we change the number of array's device after device is removed from array, then add the device back to array, we can see that device is added as active role instead of spare which we expected. Please see the below link for details: https://marc.info/?l=linux-raid&m=153736982015076&w=2 This is caused by that we prefer to use device's previous role which is recorded by saved_raid_disk, but we should respect the new number of conf->raid_disks since it could be changed after device is removed. Reported-by: Gioh Kim Tested-by: Gioh Kim Acked-by: Guoqing Jiang Signed-off-by: Shaohua Li Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

md: fix NULL dereference of mddev->pers in remove_and_add_spares()

2018-08-06T14:24:35+00:00

[ Upstream commit c42a0e2675721e1444f56e6132a07b7b1ec169ac ] We met NULL pointer BUG as follow: [ 151.760358] BUG: unable to handle kernel NULL pointer dereference at 0000000000000060 [ 151.761340] PGD 80000001011eb067 P4D 80000001011eb067 PUD 1011ea067 PMD 0 [ 151.762039] Oops: 0000 [#1] SMP PTI [ 151.762406] Modules linked in: [ 151.762723] CPU: 2 PID: 3561 Comm: mdadm-test Kdump: loaded Not tainted 4.17.0-rc1+ #238 [ 151.763542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014 [ 151.764432] RIP: 0010:remove_and_add_spares.part.56+0x13c/0x3a0 [ 151.765061] RSP: 0018:ffffc90001d7fcd8 EFLAGS: 00010246 [ 151.765590] RAX: 0000000000000000 RBX: ffff88013601d600 RCX: 0000000000000000 [ 151.766306] RDX: 0000000000000000 RSI: ffff88013601d600 RDI: ffff880136187000 [ 151.767014] RBP: ffff880136187018 R08: 0000000000000003 R09: 0000000000000051 [ 151.767728] R10: ffffc90001d7fed8 R11: 0000000000000000 R12: ffff88013601d600 [ 151.768447] R13: ffff8801298b1300 R14: ffff880136187000 R15: 0000000000000000 [ 151.769160] FS: 00007f2624276700(0000) GS:ffff88013ae80000(0000) knlGS:0000000000000000 [ 151.769971] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 151.770554] CR2: 0000000000000060 CR3: 0000000111aac000 CR4: 00000000000006e0 [ 151.771272] Call Trace: [ 151.771542] md_ioctl+0x1df2/0x1e10 [ 151.771906] ? __switch_to+0x129/0x440 [ 151.772295] ? __schedule+0x244/0x850 [ 151.772672] blkdev_ioctl+0x4bd/0x970 [ 151.773048] block_ioctl+0x39/0x40 [ 151.773402] do_vfs_ioctl+0xa4/0x610 [ 151.773770] ? dput.part.23+0x87/0x100 [ 151.774151] ksys_ioctl+0x70/0x80 [ 151.774493] __x64_sys_ioctl+0x16/0x20 [ 151.774877] do_syscall_64+0x5b/0x180 [ 151.775258] entry_SYSCALL_64_after_hwframe+0x44/0xa9 For raid6, when two disk of the array are offline, two spare disks can be added into the array. Before spare disks recovery completing, system reboot and mdadm thinks it is ok to restart the degraded array by md_ioctl(). Since disks in raid6 is not only_parity(), raid5_run() will abort, when there is no PPL feature or not setting 'start_dirty_degraded' parameter. Therefore, mddev->pers is NULL. But, mddev->raid_disks has been set and it will not be cleared when raid5_run abort. md_ioctl() can execute cmd 'HOT_REMOVE_DISK' to remove a disk by mdadm, which will cause NULL pointer dereference in remove_and_add_spares() finally. Signed-off-by: Yufen Yu Signed-off-by: Shaohua Li Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman