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Message-ID: <20240815181739.GE25962@twin.jikos.cz>
Date: Thu, 15 Aug 2024 20:17:39 +0200
From: David Sterba <dsterba@...e.cz>
To: Johannes Thumshirn <jth@...nel.org>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
David Sterba <dsterba@...e.com>,
"open list:BTRFS FILE SYSTEM" <linux-btrfs@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>,
Johannes Thumshirn <johannes.thumshirn@....com>,
Filipe Manana <fdmanana@...e.com>
Subject: Re: [PATCH] btrfs: don't take dev_replace rwsem on task already
holding it
On Thu, Aug 15, 2024 at 02:57:05PM +0200, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <johannes.thumshirn@....com>
>
> Running fstests btrfs/011 with MKFS_OPTIONS="-O rst" to force the usage of
> the RAID stripe-tree, we get the following splat from lockdep:
>
> BTRFS info (device sdd): dev_replace from /dev/sdd (devid 1) to /dev/sdb started
>
> ============================================
> WARNING: possible recursive locking detected
> 6.11.0-rc3-btrfs-for-next #599 Not tainted
> --------------------------------------------
> btrfs/2326 is trying to acquire lock:
> ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250
>
> but task is already holding lock:
> ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&fs_info->dev_replace.rwsem);
> lock(&fs_info->dev_replace.rwsem);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 1 lock held by btrfs/2326:
> #0: ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 2326 Comm: btrfs Not tainted 6.11.0-rc3-btrfs-for-next #599
> Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> Call Trace:
> <TASK>
> dump_stack_lvl+0x5b/0x80
> __lock_acquire+0x2798/0x69d0
> ? __pfx___lock_acquire+0x10/0x10
> ? __pfx___lock_acquire+0x10/0x10
> lock_acquire+0x19d/0x4a0
> ? btrfs_map_block+0x39f/0x2250
> ? __pfx_lock_acquire+0x10/0x10
> ? find_held_lock+0x2d/0x110
> ? lock_is_held_type+0x8f/0x100
> down_read+0x8e/0x440
> ? btrfs_map_block+0x39f/0x2250
> ? __pfx_down_read+0x10/0x10
> ? do_raw_read_unlock+0x44/0x70
> ? _raw_read_unlock+0x23/0x40
> btrfs_map_block+0x39f/0x2250
> ? btrfs_dev_replace_by_ioctl+0xd69/0x1d00
> ? btrfs_bio_counter_inc_blocked+0xd9/0x2e0
> ? __kasan_slab_alloc+0x6e/0x70
> ? __pfx_btrfs_map_block+0x10/0x10
> ? __pfx_btrfs_bio_counter_inc_blocked+0x10/0x10
> ? kmem_cache_alloc_noprof+0x1f2/0x300
> ? mempool_alloc_noprof+0xed/0x2b0
> btrfs_submit_chunk+0x28d/0x17e0
> ? __pfx_btrfs_submit_chunk+0x10/0x10
> ? bvec_alloc+0xd7/0x1b0
> ? bio_add_folio+0x171/0x270
> ? __pfx_bio_add_folio+0x10/0x10
> ? __kasan_check_read+0x20/0x20
> btrfs_submit_bio+0x37/0x80
> read_extent_buffer_pages+0x3df/0x6c0
> btrfs_read_extent_buffer+0x13e/0x5f0
> read_tree_block+0x81/0xe0
> read_block_for_search+0x4bd/0x7a0
> ? __pfx_read_block_for_search+0x10/0x10
> btrfs_search_slot+0x78d/0x2720
> ? __pfx_btrfs_search_slot+0x10/0x10
> ? lock_is_held_type+0x8f/0x100
> ? kasan_save_track+0x14/0x30
> ? __kasan_slab_alloc+0x6e/0x70
> ? kmem_cache_alloc_noprof+0x1f2/0x300
> btrfs_get_raid_extent_offset+0x181/0x820
> ? __pfx_lock_acquire+0x10/0x10
> ? __pfx_btrfs_get_raid_extent_offset+0x10/0x10
> ? down_read+0x194/0x440
> ? __pfx_down_read+0x10/0x10
> ? do_raw_read_unlock+0x44/0x70
> ? _raw_read_unlock+0x23/0x40
> btrfs_map_block+0x5b5/0x2250
> ? __pfx_btrfs_map_block+0x10/0x10
> scrub_submit_initial_read+0x8fe/0x11b0
> ? __pfx_scrub_submit_initial_read+0x10/0x10
> submit_initial_group_read+0x161/0x3a0
> ? lock_release+0x20e/0x710
> ? __pfx_submit_initial_group_read+0x10/0x10
> ? __pfx_lock_release+0x10/0x10
> scrub_simple_mirror.isra.0+0x3eb/0x580
> scrub_stripe+0xe4d/0x1440
> ? lock_release+0x20e/0x710
> ? __pfx_scrub_stripe+0x10/0x10
> ? __pfx_lock_release+0x10/0x10
> ? do_raw_read_unlock+0x44/0x70
> ? _raw_read_unlock+0x23/0x40
> scrub_chunk+0x257/0x4a0
> scrub_enumerate_chunks+0x64c/0xf70
> ? __mutex_unlock_slowpath+0x147/0x5f0
> ? __pfx_scrub_enumerate_chunks+0x10/0x10
> ? bit_wait_timeout+0xb0/0x170
> ? __up_read+0x189/0x700
> ? scrub_workers_get+0x231/0x300
> ? up_write+0x490/0x4f0
> btrfs_scrub_dev+0x52e/0xcd0
> ? create_pending_snapshots+0x230/0x250
> ? __pfx_btrfs_scrub_dev+0x10/0x10
> btrfs_dev_replace_by_ioctl+0xd69/0x1d00
> ? lock_acquire+0x19d/0x4a0
> ? __pfx_btrfs_dev_replace_by_ioctl+0x10/0x10
> ? lock_release+0x20e/0x710
> ? btrfs_ioctl+0xa09/0x74f0
> ? __pfx_lock_release+0x10/0x10
> ? do_raw_spin_lock+0x11e/0x240
> ? __pfx_do_raw_spin_lock+0x10/0x10
> btrfs_ioctl+0xa14/0x74f0
> ? lock_acquire+0x19d/0x4a0
> ? find_held_lock+0x2d/0x110
> ? __pfx_btrfs_ioctl+0x10/0x10
> ? lock_release+0x20e/0x710
> ? do_sigaction+0x3f0/0x860
> ? __pfx_do_vfs_ioctl+0x10/0x10
> ? do_raw_spin_lock+0x11e/0x240
> ? lockdep_hardirqs_on_prepare+0x270/0x3e0
> ? _raw_spin_unlock_irq+0x28/0x50
> ? do_sigaction+0x3f0/0x860
> ? __pfx_do_sigaction+0x10/0x10
> ? __x64_sys_rt_sigaction+0x18e/0x1e0
> ? __pfx___x64_sys_rt_sigaction+0x10/0x10
> ? __x64_sys_close+0x7c/0xd0
> __x64_sys_ioctl+0x137/0x190
> do_syscall_64+0x71/0x140
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
> RIP: 0033:0x7f0bd1114f9b
> Code: Unable to access opcode bytes at 0x7f0bd1114f71.
> RSP: 002b:00007ffc8a8c3130 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f0bd1114f9b
> RDX: 00007ffc8a8c35e0 RSI: 00000000ca289435 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000007
> R10: 0000000000000008 R11: 0000000000000246 R12: 00007ffc8a8c6c85
> R13: 00000000398e72a0 R14: 0000000000004361 R15: 0000000000000004
> </TASK>
>
> This happens because on RAID stripe-tree filesystems we recurse back into
> btrfs_map_block() on scrub to perform the logical to device physical
> mapping.
>
> But as the device replace task is already holding the dev_replace::rwsem
> we deadlock.
>
> So don't take the dev_replace::rwsem in case our task is the task performing
> the device replace.
>
> Suggested-by: Filipe Manana <fdmanana@...e.com>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
> fs/btrfs/dev-replace.c | 2 ++
> fs/btrfs/fs.h | 2 ++
> fs/btrfs/volumes.c | 4 +++-
> 3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> index 83d5cdd77f29..604399e59a3d 100644
> --- a/fs/btrfs/dev-replace.c
> +++ b/fs/btrfs/dev-replace.c
> @@ -641,6 +641,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
> return ret;
>
> down_write(&dev_replace->rwsem);
> + dev_replace->replace_task = current;
> switch (dev_replace->replace_state) {
> case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
> case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
> @@ -994,6 +995,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
> list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
> fs_devices->rw_devices++;
>
> + dev_replace->replace_task = NULL;
> up_write(&dev_replace->rwsem);
> btrfs_rm_dev_replace_blocked(fs_info);
>
> diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
> index 3d6d4b503220..53824da92cc3 100644
> --- a/fs/btrfs/fs.h
> +++ b/fs/btrfs/fs.h
> @@ -317,6 +317,8 @@ struct btrfs_dev_replace {
>
> struct percpu_counter bio_counter;
> wait_queue_head_t replace_wait;
> +
> + struct task_struct *replace_task;
Wasn't the idea to use pid for that, and not a raw pointer?
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