btrfs: allocate scrub workqueues outside of locks
I got the following lockdep splat while testing: ====================================================== WARNING: possible circular locking dependency detected 5.8.0-rc7-00172-g021118712e59 #932 Not tainted ------------------------------------------------------ btrfs/229626 is trying to acquire lock: ffffffff828513f0 (cpu_hotplug_lock){++++}-{0:0}, at: alloc_workqueue+0x378/0x450 but task is already holding lock: ffff889dd3889518 (&fs_info->scrub_lock){+.+.}-{3:3}, at: btrfs_scrub_dev+0x11c/0x630 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (&fs_info->scrub_lock){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 btrfs_scrub_dev+0x11c/0x630 btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4 btrfs_ioctl+0x2799/0x30a0 ksys_ioctl+0x83/0xc0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x50/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #6 (&fs_devs->device_list_mutex){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 btrfs_run_dev_stats+0x49/0x480 commit_cowonly_roots+0xb5/0x2a0 btrfs_commit_transaction+0x516/0xa60 sync_filesystem+0x6b/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0xe/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x29/0x60 cleanup_mnt+0xb8/0x140 task_work_run+0x6d/0xb0 __prepare_exit_to_usermode+0x1cc/0x1e0 do_syscall_64+0x5c/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #5 (&fs_info->tree_log_mutex){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 btrfs_commit_transaction+0x4bb/0xa60 sync_filesystem+0x6b/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0xe/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x29/0x60 cleanup_mnt+0xb8/0x140 task_work_run+0x6d/0xb0 __prepare_exit_to_usermode+0x1cc/0x1e0 do_syscall_64+0x5c/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #4 (&fs_info->reloc_mutex){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 btrfs_record_root_in_trans+0x43/0x70 start_transaction+0xd1/0x5d0 btrfs_dirty_inode+0x42/0xd0 touch_atime+0xa1/0xd0 btrfs_file_mmap+0x3f/0x60 mmap_region+0x3a4/0x640 do_mmap+0x376/0x580 vm_mmap_pgoff+0xd5/0x120 ksys_mmap_pgoff+0x193/0x230 do_syscall_64+0x50/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #3 (&mm->mmap_lock#2){++++}-{3:3}: __might_fault+0x68/0x90 _copy_to_user+0x1e/0x80 perf_read+0x141/0x2c0 vfs_read+0xad/0x1b0 ksys_read+0x5f/0xe0 do_syscall_64+0x50/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (&cpuctx_mutex){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 perf_event_init_cpu+0x88/0x150 perf_event_init+0x1db/0x20b start_kernel+0x3ae/0x53c secondary_startup_64+0xa4/0xb0 -> #1 (pmus_lock){+.+.}-{3:3}: __mutex_lock+0x9f/0x930 perf_event_init_cpu+0x4f/0x150 cpuhp_invoke_callback+0xb1/0x900 _cpu_up.constprop.26+0x9f/0x130 cpu_up+0x7b/0xc0 bringup_nonboot_cpus+0x4f/0x60 smp_init+0x26/0x71 kernel_init_freeable+0x110/0x258 kernel_init+0xa/0x103 ret_from_fork+0x1f/0x30 -> #0 (cpu_hotplug_lock){++++}-{0:0}: __lock_acquire+0x1272/0x2310 lock_acquire+0x9e/0x360 cpus_read_lock+0x39/0xb0 alloc_workqueue+0x378/0x450 __btrfs_alloc_workqueue+0x15d/0x200 btrfs_alloc_workqueue+0x51/0x160 scrub_workers_get+0x5a/0x170 btrfs_scrub_dev+0x18c/0x630 btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4 btrfs_ioctl+0x2799/0x30a0 ksys_ioctl+0x83/0xc0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x50/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Chain exists of: cpu_hotplug_lock --> &fs_devs->device_list_mutex --> &fs_info->scrub_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->scrub_lock); lock(&fs_devs->device_list_mutex); lock(&fs_info->scrub_lock); lock(cpu_hotplug_lock); *** DEADLOCK *** 2 locks held by btrfs/229626: #0: ffff88bfe8bb86e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_scrub_dev+0xbd/0x630 #1: ffff889dd3889518 (&fs_info->scrub_lock){+.+.}-{3:3}, at: btrfs_scrub_dev+0x11c/0x630 stack backtrace: CPU: 15 PID: 229626 Comm: btrfs Kdump: loaded Not tainted 5.8.0-rc7-00172-g021118712e59 #932 Hardware name: Quanta Tioga Pass Single Side 01-0030993006/Tioga Pass Single Side, BIOS F08_3A18 12/20/2018 Call Trace: dump_stack+0x78/0xa0 check_noncircular+0x165/0x180 __lock_acquire+0x1272/0x2310 lock_acquire+0x9e/0x360 ? alloc_workqueue+0x378/0x450 cpus_read_lock+0x39/0xb0 ? alloc_workqueue+0x378/0x450 alloc_workqueue+0x378/0x450 ? rcu_read_lock_sched_held+0x52/0x80 __btrfs_alloc_workqueue+0x15d/0x200 btrfs_alloc_workqueue+0x51/0x160 scrub_workers_get+0x5a/0x170 btrfs_scrub_dev+0x18c/0x630 ? start_transaction+0xd1/0x5d0 btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4 btrfs_ioctl+0x2799/0x30a0 ? do_sigaction+0x102/0x250 ? lockdep_hardirqs_on_prepare+0xca/0x160 ? _raw_spin_unlock_irq+0x24/0x30 ? trace_hardirqs_on+0x1c/0xe0 ? _raw_spin_unlock_irq+0x24/0x30 ? do_sigaction+0x102/0x250 ? ksys_ioctl+0x83/0xc0 ksys_ioctl+0x83/0xc0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x50/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This happens because we're allocating the scrub workqueues under the scrub and device list mutex, which brings in a whole host of other dependencies. Because the work queue allocation is done with GFP_KERNEL, it can trigger reclaim, which can lead to a transaction commit, which in turns needs the device_list_mutex, it can lead to a deadlock. A different problem for which this fix is a solution. Fix this by moving the actual allocation outside of the scrub lock, and then only take the lock once we're ready to actually assign them to the fs_info. We'll now have to cleanup the workqueues in a few more places, so I've added a helper to do the refcount dance to safely free the workqueues. CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik
David Sterba
Родитель
a48b73eca4
Коммит
e89c4a9c8e
126
fs/btrfs/scrub.c
126
fs/btrfs/scrub.c
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@ -3716,50 +3716,84 @@ static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
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return 0;
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}
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static void scrub_workers_put(struct btrfs_fs_info *fs_info)
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{
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if (refcount_dec_and_mutex_lock(&fs_info->scrub_workers_refcnt,
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&fs_info->scrub_lock)) {
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struct btrfs_workqueue *scrub_workers = NULL;
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struct btrfs_workqueue *scrub_wr_comp = NULL;
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struct btrfs_workqueue *scrub_parity = NULL;
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scrub_workers = fs_info->scrub_workers;
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scrub_wr_comp = fs_info->scrub_wr_completion_workers;
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scrub_parity = fs_info->scrub_parity_workers;
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fs_info->scrub_workers = NULL;
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fs_info->scrub_wr_completion_workers = NULL;
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fs_info->scrub_parity_workers = NULL;
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mutex_unlock(&fs_info->scrub_lock);
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btrfs_destroy_workqueue(scrub_workers);
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btrfs_destroy_workqueue(scrub_wr_comp);
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btrfs_destroy_workqueue(scrub_parity);
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}
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}
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/*
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* get a reference count on fs_info->scrub_workers. start worker if necessary
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*/
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static noinline_for_stack int scrub_workers_get(struct btrfs_fs_info *fs_info,
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int is_dev_replace)
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{
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struct btrfs_workqueue *scrub_workers = NULL;
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struct btrfs_workqueue *scrub_wr_comp = NULL;
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struct btrfs_workqueue *scrub_parity = NULL;
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unsigned int flags = WQ_FREEZABLE | WQ_UNBOUND;
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int max_active = fs_info->thread_pool_size;
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int ret = -ENOMEM;
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lockdep_assert_held(&fs_info->scrub_lock);
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if (refcount_inc_not_zero(&fs_info->scrub_workers_refcnt))
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return 0;
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scrub_workers = btrfs_alloc_workqueue(fs_info, "scrub", flags,
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is_dev_replace ? 1 : max_active, 4);
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if (!scrub_workers)
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goto fail_scrub_workers;
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scrub_wr_comp = btrfs_alloc_workqueue(fs_info, "scrubwrc", flags,
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max_active, 2);
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if (!scrub_wr_comp)
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goto fail_scrub_wr_completion_workers;
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scrub_parity = btrfs_alloc_workqueue(fs_info, "scrubparity", flags,
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max_active, 2);
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if (!scrub_parity)
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goto fail_scrub_parity_workers;
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mutex_lock(&fs_info->scrub_lock);
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if (refcount_read(&fs_info->scrub_workers_refcnt) == 0) {
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ASSERT(fs_info->scrub_workers == NULL);
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fs_info->scrub_workers = btrfs_alloc_workqueue(fs_info, "scrub",
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flags, is_dev_replace ? 1 : max_active, 4);
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if (!fs_info->scrub_workers)
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goto fail_scrub_workers;
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ASSERT(fs_info->scrub_wr_completion_workers == NULL);
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fs_info->scrub_wr_completion_workers =
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btrfs_alloc_workqueue(fs_info, "scrubwrc", flags,
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max_active, 2);
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if (!fs_info->scrub_wr_completion_workers)
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goto fail_scrub_wr_completion_workers;
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ASSERT(fs_info->scrub_parity_workers == NULL);
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fs_info->scrub_parity_workers =
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btrfs_alloc_workqueue(fs_info, "scrubparity", flags,
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max_active, 2);
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if (!fs_info->scrub_parity_workers)
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goto fail_scrub_parity_workers;
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ASSERT(fs_info->scrub_workers == NULL &&
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fs_info->scrub_wr_completion_workers == NULL &&
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fs_info->scrub_parity_workers == NULL);
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fs_info->scrub_workers = scrub_workers;
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fs_info->scrub_wr_completion_workers = scrub_wr_comp;
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fs_info->scrub_parity_workers = scrub_parity;
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refcount_set(&fs_info->scrub_workers_refcnt, 1);
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} else {
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refcount_inc(&fs_info->scrub_workers_refcnt);
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mutex_unlock(&fs_info->scrub_lock);
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return 0;
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}
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return 0;
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/* Other thread raced in and created the workers for us */
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refcount_inc(&fs_info->scrub_workers_refcnt);
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mutex_unlock(&fs_info->scrub_lock);
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ret = 0;
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btrfs_destroy_workqueue(scrub_parity);
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fail_scrub_parity_workers:
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btrfs_destroy_workqueue(fs_info->scrub_wr_completion_workers);
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btrfs_destroy_workqueue(scrub_wr_comp);
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fail_scrub_wr_completion_workers:
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btrfs_destroy_workqueue(fs_info->scrub_workers);
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btrfs_destroy_workqueue(scrub_workers);
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fail_scrub_workers:
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return -ENOMEM;
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return ret;
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}
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int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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@ -3770,9 +3804,6 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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int ret;
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struct btrfs_device *dev;
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unsigned int nofs_flag;
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struct btrfs_workqueue *scrub_workers = NULL;
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struct btrfs_workqueue *scrub_wr_comp = NULL;
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struct btrfs_workqueue *scrub_parity = NULL;
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if (btrfs_fs_closing(fs_info))
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return -EAGAIN;
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@ -3819,13 +3850,17 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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if (IS_ERR(sctx))
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return PTR_ERR(sctx);
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ret = scrub_workers_get(fs_info, is_dev_replace);
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if (ret)
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goto out_free_ctx;
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mutex_lock(&fs_info->fs_devices->device_list_mutex);
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dev = btrfs_find_device(fs_info->fs_devices, devid, NULL, NULL, true);
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if (!dev || (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) &&
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!is_dev_replace)) {
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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ret = -ENODEV;
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goto out_free_ctx;
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goto out;
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}
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if (!is_dev_replace && !readonly &&
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@ -3834,7 +3869,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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btrfs_err_in_rcu(fs_info, "scrub: device %s is not writable",
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rcu_str_deref(dev->name));
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ret = -EROFS;
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goto out_free_ctx;
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goto out;
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}
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mutex_lock(&fs_info->scrub_lock);
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@ -3843,7 +3878,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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mutex_unlock(&fs_info->scrub_lock);
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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ret = -EIO;
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goto out_free_ctx;
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goto out;
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}
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down_read(&fs_info->dev_replace.rwsem);
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@ -3854,17 +3889,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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mutex_unlock(&fs_info->scrub_lock);
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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ret = -EINPROGRESS;
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goto out_free_ctx;
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goto out;
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}
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up_read(&fs_info->dev_replace.rwsem);
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ret = scrub_workers_get(fs_info, is_dev_replace);
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if (ret) {
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mutex_unlock(&fs_info->scrub_lock);
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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goto out_free_ctx;
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}
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sctx->readonly = readonly;
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dev->scrub_ctx = sctx;
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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@ -3917,24 +3945,14 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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mutex_lock(&fs_info->scrub_lock);
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dev->scrub_ctx = NULL;
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if (refcount_dec_and_test(&fs_info->scrub_workers_refcnt)) {
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scrub_workers = fs_info->scrub_workers;
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scrub_wr_comp = fs_info->scrub_wr_completion_workers;
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scrub_parity = fs_info->scrub_parity_workers;
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fs_info->scrub_workers = NULL;
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fs_info->scrub_wr_completion_workers = NULL;
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fs_info->scrub_parity_workers = NULL;
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}
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mutex_unlock(&fs_info->scrub_lock);
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btrfs_destroy_workqueue(scrub_workers);
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btrfs_destroy_workqueue(scrub_wr_comp);
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btrfs_destroy_workqueue(scrub_parity);
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scrub_workers_put(fs_info);
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scrub_put_ctx(sctx);
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return ret;
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out:
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scrub_workers_put(fs_info);
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out_free_ctx:
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scrub_free_ctx(sctx);
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