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Anand Jain fb4c7d2923 btrfs: fix lockdep warning while mounting sprout fs 
[ Upstream commit c124706900c20dee70f921bb3a90492431561a0a ]

Following test case reproduces lockdep warning.

  Test case:

  $ mkfs.btrfs -f <dev1>
  $ btrfstune -S 1 <dev1>
  $ mount <dev1> <mnt>
  $ btrfs device add <dev2> <mnt> -f
  $ umount <mnt>
  $ mount <dev2> <mnt>
  $ umount <mnt>

The warning claims a possible ABBA deadlock between the threads
initiated by [#1] btrfs device add and [#0] the mount.

  [ 540.743122] WARNING: possible circular locking dependency detected
  [ 540.743129] 5.11.0-rc7+ #5 Not tainted
  [ 540.743135] ------------------------------------------------------
  [ 540.743142] mount/2515 is trying to acquire lock:
  [ 540.743149] ffffa0c5544c2ce0 (&fs_devs->device_list_mutex){+.+.}-{4:4}, at: clone_fs_devices+0x6d/0x210 [btrfs]
  [ 540.743458] but task is already holding lock:
  [ 540.743461] ffffa0c54a7932b8 (btrfs-chunk-00){++++}-{4:4}, at: __btrfs_tree_read_lock+0x32/0x200 [btrfs]
  [ 540.743541] which lock already depends on the new lock.
  [ 540.743543] the existing dependency chain (in reverse order) is:

  [ 540.743546] -> #1 (btrfs-chunk-00){++++}-{4:4}:
  [ 540.743566] down_read_nested+0x48/0x2b0
  [ 540.743585] __btrfs_tree_read_lock+0x32/0x200 [btrfs]
  [ 540.743650] btrfs_read_lock_root_node+0x70/0x200 [btrfs]
  [ 540.743733] btrfs_search_slot+0x6c6/0xe00 [btrfs]
  [ 540.743785] btrfs_update_device+0x83/0x260 [btrfs]
  [ 540.743849] btrfs_finish_chunk_alloc+0x13f/0x660 [btrfs] <--- device_list_mutex
  [ 540.743911] btrfs_create_pending_block_groups+0x18d/0x3f0 [btrfs]
  [ 540.743982] btrfs_commit_transaction+0x86/0x1260 [btrfs]
  [ 540.744037] btrfs_init_new_device+0x1600/0x1dd0 [btrfs]
  [ 540.744101] btrfs_ioctl+0x1c77/0x24c0 [btrfs]
  [ 540.744166] __x64_sys_ioctl+0xe4/0x140
  [ 540.744170] do_syscall_64+0x4b/0x80
  [ 540.744174] entry_SYSCALL_64_after_hwframe+0x44/0xa9

  [ 540.744180] -> #0 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
  [ 540.744184] __lock_acquire+0x155f/0x2360
  [ 540.744188] lock_acquire+0x10b/0x5c0
  [ 540.744190] __mutex_lock+0xb1/0xf80
  [ 540.744193] mutex_lock_nested+0x27/0x30
  [ 540.744196] clone_fs_devices+0x6d/0x210 [btrfs]
  [ 540.744270] btrfs_read_chunk_tree+0x3c7/0xbb0 [btrfs]
  [ 540.744336] open_ctree+0xf6e/0x2074 [btrfs]
  [ 540.744406] btrfs_mount_root.cold.72+0x16/0x127 [btrfs]
  [ 540.744472] legacy_get_tree+0x38/0x90
  [ 540.744475] vfs_get_tree+0x30/0x140
  [ 540.744478] fc_mount+0x16/0x60
  [ 540.744482] vfs_kern_mount+0x91/0x100
  [ 540.744484] btrfs_mount+0x1e6/0x670 [btrfs]
  [ 540.744536] legacy_get_tree+0x38/0x90
  [ 540.744537] vfs_get_tree+0x30/0x140
  [ 540.744539] path_mount+0x8d8/0x1070
  [ 540.744541] do_mount+0x8d/0xc0
  [ 540.744543] __x64_sys_mount+0x125/0x160
  [ 540.744545] do_syscall_64+0x4b/0x80
  [ 540.744547] entry_SYSCALL_64_after_hwframe+0x44/0xa9

  [ 540.744551] other info that might help us debug this:
  [ 540.744552] Possible unsafe locking scenario:

  [ 540.744553] CPU0 				CPU1
  [ 540.744554] ---- 				----
  [ 540.744555] lock(btrfs-chunk-00);
  [ 540.744557] 					lock(&fs_devs->device_list_mutex);
  [ 540.744560] 					lock(btrfs-chunk-00);
  [ 540.744562] lock(&fs_devs->device_list_mutex);
  [ 540.744564]
   *** DEADLOCK ***

  [ 540.744565] 3 locks held by mount/2515:
  [ 540.744567] #0: ffffa0c56bf7a0e0 (&type->s_umount_key#42/1){+.+.}-{4:4}, at: alloc_super.isra.16+0xdf/0x450
  [ 540.744574] #1: ffffffffc05a9628 (uuid_mutex){+.+.}-{4:4}, at: btrfs_read_chunk_tree+0x63/0xbb0 [btrfs]
  [ 540.744640] #2: ffffa0c54a7932b8 (btrfs-chunk-00){++++}-{4:4}, at: __btrfs_tree_read_lock+0x32/0x200 [btrfs]
  [ 540.744708]
   stack backtrace:
  [ 540.744712] CPU: 2 PID: 2515 Comm: mount Not tainted 5.11.0-rc7+ #5

But the device_list_mutex in clone_fs_devices() is redundant, as
explained below.  Two threads [1]  and [2] (below) could lead to
clone_fs_device().

  [1]
  open_ctree <== mount sprout fs
   btrfs_read_chunk_tree()
    mutex_lock(&uuid_mutex) <== global lock
    read_one_dev()
     open_seed_devices()
      clone_fs_devices() <== seed fs_devices
       mutex_lock(&orig->device_list_mutex) <== seed fs_devices

  [2]
  btrfs_init_new_device() <== sprouting
   mutex_lock(&uuid_mutex); <== global lock
   btrfs_prepare_sprout()
     lockdep_assert_held(&uuid_mutex)
     clone_fs_devices(seed_fs_device) <== seed fs_devices

Both of these threads hold uuid_mutex which is sufficient to protect
getting the seed device(s) freed while we are trying to clone it for
sprouting [2] or mounting a sprout [1] (as above). A mounted seed device
can not free/write/replace because it is read-only. An unmounted seed
device can be freed by btrfs_free_stale_devices(), but it needs
uuid_mutex.  So this patch removes the unnecessary device_list_mutex in
clone_fs_devices().  And adds a lockdep_assert_held(&uuid_mutex) in
clone_fs_devices().

Reported-by: Su Yue <l@damenly.su>
Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2021-09-26 14:07:12 +02:00
..
tests btrfs: Correctly handle empty trees in find_first_clear_extent_bit 2020-02-11 04:35:34 -08:00
Kconfig btrfs: disable build on platforms having page size 256K 2021-07-14 16:53:14 +02:00
Makefile btrfs: migrate the block group lookup code 2019-09-09 14:59:04 +02:00
acl.c btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
async-thread.c Btrfs: fix crash during unmount due to race with delayed inode workers 2020-04-17 10:50:15 +02:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-04-17 10:50:15 +02:00
backref.c btrfs: backref, use correct count to resolve normal data refs 2021-02-07 15:35:47 +01:00
backref.h btrfs: fiemap: preallocate ulists for btrfs_check_shared 2019-07-01 13:34:53 +02:00
block-group.c btrfs: delete duplicated words + other fixes in comments 2021-08-08 09:04:07 +02:00
block-group.h btrfs: scrub: Don't check free space before marking a block group RO 2021-03-20 10:39:46 +01:00
block-rsv.c btrfs: force chunk allocation if our global rsv is larger than metadata 2020-06-22 09:31:13 +02:00
block-rsv.h btrfs: migrate the global_block_rsv helpers to block-rsv.c 2019-07-02 12:30:55 +02:00
btrfs_inode.h btrfs: fix race between marking inode needs to be logged and log syncing 2021-09-03 10:08:15 +02:00
check-integrity.c btrfs: fix possible NULL-pointer dereference in integrity checks 2020-02-24 08:36:53 +01:00
check-integrity.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
compression.c btrfs: mark compressed range uptodate only if all bio succeed 2021-08-04 12:27:37 +02:00
compression.h btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
ctree.c btrfs: delete duplicated words + other fixes in comments 2021-08-08 09:04:07 +02:00
ctree.h btrfs: fix lockdep splat when enabling and disabling qgroups 2021-08-15 13:08:05 +02:00
delalloc-space.c btrfs: make btrfs_qgroup_reserve_data take btrfs_inode 2021-08-15 13:08:04 +02:00
delalloc-space.h btrfs: migrate the delalloc space stuff to it's own home 2019-07-04 17:26:17 +02:00
delayed-inode.c btrfs: don't flush from btrfs_delayed_inode_reserve_metadata 2021-08-15 13:08:06 +02:00
delayed-inode.h Btrfs: delayed-inode: use rb_first_cached for ins_root and del_root 2018-10-15 17:23:33 +02:00
delayed-ref.c Btrfs: fix race between adding and putting tree mod seq elements and nodes 2020-02-11 04:35:34 -08:00
delayed-ref.h btrfs: migrate the delayed refs rsv code 2019-07-04 17:26:17 +02:00
dev-replace.c btrfs: dev-replace: fail mount if we don't have replace item with target device 2020-11-18 19:20:29 +01:00
dev-replace.h btrfs: get fs_info from trans in btrfs_run_dev_replace 2019-04-29 19:02:43 +02:00
dir-item.c btrfs: remove unused parameter fs_info from btrfs_extend_item 2019-04-29 19:02:50 +02:00
disk-io.c btrfs: fix upper limit for max_inline for page size 64K 2021-09-22 12:26:38 +02:00
disk-io.h btrfs: Make reada_tree_block_flagged private 2019-09-09 14:59:11 +02:00
export.c btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
extent-tree.c btrfs: check for missing device in btrfs_trim_fs 2021-07-28 13:31:00 +02:00
extent_io.c btrfs: delete duplicated words + other fixes in comments 2021-08-08 09:04:07 +02:00
extent_io.h btrfs: trim: fix underflow in trim length to prevent access beyond device boundary 2020-12-30 11:51:37 +01:00
extent_map.c Btrfs: fix race between using extent maps and merging them 2020-02-19 19:53:00 +01:00
extent_map.h btrfs: Remove impossible condition from mergable_maps 2019-02-25 14:13:21 +01:00
file-item.c btrfs: fix error handling in btrfs_del_csums 2021-06-10 13:37:13 +02:00
file.c btrfs: fix race between marking inode needs to be logged and log syncing 2021-09-03 10:08:15 +02:00
free-space-cache.c btrfs: delete duplicated words + other fixes in comments 2021-08-08 09:04:07 +02:00
free-space-cache.h btrfs: move struct io_ctl to free-space-cache.h 2019-09-09 14:59:15 +02:00
free-space-tree.c btrfs: fix possible free space tree corruption with online conversion 2021-02-03 23:25:57 +01:00
free-space-tree.h btrfs: move basic block_group definitions to their own header 2019-09-09 14:59:03 +02:00
inode-item.c btrfs: Make btrfs_find_name_in_ext_backref return struct btrfs_inode_extref 2019-09-09 14:59:16 +02:00
inode-map.c btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents() 2019-10-15 18:50:07 +02:00
inode-map.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
inode.c btrfs: wake up async_delalloc_pages waiters after submit 2021-09-22 12:26:19 +02:00
ioctl.c btrfs: fix metadata extent leak after failure to create subvolume 2021-05-11 14:04:04 +02:00
locking.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
locking.h btrfs: Remove unused locking functions 2019-09-09 14:58:59 +02:00
lzo.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
misc.h btrfs: move math functions to misc.h 2019-09-09 14:59:15 +02:00
ordered-data.c Btrfs: fix btrfs_wait_ordered_range() so that it waits for all ordered extents 2020-02-28 17:22:24 +01:00
ordered-data.h btrfs: don't assume ordered sums to be 4 bytes 2019-07-01 13:35:00 +02:00
orphan.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
print-tree.c btrfs: require only sector size alignment for parent eb bytenr 2020-09-17 13:47:51 +02:00
print-tree.h btrfs: print-tree: debugging output enhancement 2018-04-20 19:18:16 +02:00
props.c btrfs: rename the btrfs_calc_*_metadata_size helpers 2019-09-09 14:59:13 +02:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: export and rename qgroup_reserve_meta 2021-08-15 13:08:06 +02:00
qgroup.h btrfs: export and rename qgroup_reserve_meta 2021-08-15 13:08:06 +02:00
raid56.c btrfs: fix raid6 qstripe kmap 2021-03-09 11:09:37 +01:00
raid56.h btrfs: constify map parameter for nr_parity_stripes and nr_data_stripes 2019-07-01 13:34:58 +02:00
rcu-string.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
reada.c btrfs: fix readahead hang and use-after-free after removing a device 2020-11-05 11:43:27 +01:00
ref-verify.c btrfs: ref-verify: fix memory leak in btrfs_ref_tree_mod 2020-11-18 19:20:28 +01:00
ref-verify.h btrfs: ref-verify: Use btrfs_ref to refactor btrfs_ref_tree_mod() 2019-04-29 19:02:49 +02:00
relocation.c btrfs: convert logic BUG_ON()'s in replace_path to ASSERT()'s 2021-05-11 14:04:07 +02:00
root-tree.c btrfs: do not delete mismatched root refs 2020-01-23 08:22:40 +01:00
scrub.c btrfs: scrub: Don't check free space before marking a block group RO 2021-03-20 10:39:46 +01:00
send.c btrfs: send: fix invalid path for unlink operations after parent orphanization 2021-07-14 16:53:02 +02:00
send.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
space-info.c btrfs: take overcommit into account in inc_block_group_ro 2020-10-17 10:11:21 +02:00
space-info.h btrfs: take overcommit into account in inc_block_group_ro 2020-10-17 10:11:21 +02:00
struct-funcs.c btrfs: tie extent buffer and it's token together 2019-09-09 14:59:16 +02:00
super.c btrfs: fix transaction leak and crash after RO remount caused by qgroup rescan 2021-01-19 18:26:14 +01:00
sysfs.c btrfs: sysfs: use NOFS for device creation 2020-08-21 13:05:22 +02:00
sysfs.h btrfs: sysfs: move helper macros to sysfs.c 2019-09-09 14:59:08 +02:00
transaction.c btrfs: qgroup: remove ASYNC_COMMIT mechanism in favor of reserve retry-after-EDQUOT 2021-08-15 13:08:05 +02:00
transaction.h btrfs: fix race between marking inode needs to be logged and log syncing 2021-09-03 10:08:15 +02:00
tree-checker.c btrfs: tree-checker: do not error out if extent ref hash doesn't match 2021-06-10 13:37:01 +02:00
tree-checker.h btrfs: get fs_info from eb in btrfs_check_chunk_valid 2019-04-29 19:02:39 +02:00
tree-defrag.c btrfs: open code now trivial btrfs_set_lock_blocking 2019-02-25 14:13:27 +01:00
tree-log.c btrfs: tree-log: check btrfs_lookup_data_extent return value 2021-09-22 12:26:34 +02:00
tree-log.h btrfs: do not commit logs and transactions during link and rename operations 2021-08-08 09:04:07 +02:00
ulist.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ulist.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
uuid-tree.c btrfs: handle ENOENT in btrfs_uuid_tree_iterate 2019-12-31 16:42:05 +01:00
volumes.c btrfs: fix lockdep warning while mounting sprout fs 2021-09-26 14:07:12 +02:00
volumes.h btrfs: fix readahead hang and use-after-free after removing a device 2020-11-05 11:43:27 +01:00
xattr.c btrfs: fix warning when creating a directory with smack enabled 2021-03-09 11:09:37 +01:00
xattr.h btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
zlib.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
zstd.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00