kernel/git/stable/linux.git/fs/btrfs/backref.c, branch linux-5.9.y

btrfs: add a helper to read the tree_root commit root for backref lookup

2020-11-10T11:39:05+00:00

[ Upstream commit 49d11bead7d596e031fbd34051d8765587cd645b ] I got the following lockdep splat with tree locks converted to rwsem patches on btrfs/104: ====================================================== WARNING: possible circular locking dependency detected 5.9.0+ #102 Not tainted ------------------------------------------------------ btrfs-cleaner/903 is trying to acquire lock: ffff8e7fab6ffe30 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x170 but task is already holding lock: ffff8e7fab628a88 (&fs_info->commit_root_sem){++++}-{3:3}, at: btrfs_find_all_roots+0x41/0x80 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&fs_info->commit_root_sem){++++}-{3:3}: down_read+0x40/0x130 caching_thread+0x53/0x5a0 btrfs_work_helper+0xfa/0x520 process_one_work+0x238/0x540 worker_thread+0x55/0x3c0 kthread+0x13a/0x150 ret_from_fork+0x1f/0x30 -> #2 (&caching_ctl->mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7b0 btrfs_cache_block_group+0x1e0/0x510 find_free_extent+0xb6e/0x12f0 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb1/0x330 alloc_tree_block_no_bg_flush+0x4f/0x60 __btrfs_cow_block+0x11d/0x580 btrfs_cow_block+0x10c/0x220 commit_cowonly_roots+0x47/0x2e0 btrfs_commit_transaction+0x595/0xbd0 sync_filesystem+0x74/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0x14/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x36/0xa0 cleanup_mnt+0x12d/0x190 task_work_run+0x5c/0xa0 exit_to_user_mode_prepare+0x1df/0x200 syscall_exit_to_user_mode+0x54/0x280 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&space_info->groups_sem){++++}-{3:3}: down_read+0x40/0x130 find_free_extent+0x2ed/0x12f0 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb1/0x330 alloc_tree_block_no_bg_flush+0x4f/0x60 __btrfs_cow_block+0x11d/0x580 btrfs_cow_block+0x10c/0x220 commit_cowonly_roots+0x47/0x2e0 btrfs_commit_transaction+0x595/0xbd0 sync_filesystem+0x74/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0x14/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x36/0xa0 cleanup_mnt+0x12d/0x190 task_work_run+0x5c/0xa0 exit_to_user_mode_prepare+0x1df/0x200 syscall_exit_to_user_mode+0x54/0x280 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (btrfs-root-00){++++}-{3:3}: __lock_acquire+0x1167/0x2150 lock_acquire+0xb9/0x3d0 down_read_nested+0x43/0x130 __btrfs_tree_read_lock+0x32/0x170 __btrfs_read_lock_root_node+0x3a/0x50 btrfs_search_slot+0x614/0x9d0 btrfs_find_root+0x35/0x1b0 btrfs_read_tree_root+0x61/0x120 btrfs_get_root_ref+0x14b/0x600 find_parent_nodes+0x3e6/0x1b30 btrfs_find_all_roots_safe+0xb4/0x130 btrfs_find_all_roots+0x60/0x80 btrfs_qgroup_trace_extent_post+0x27/0x40 btrfs_add_delayed_data_ref+0x3fd/0x460 btrfs_free_extent+0x42/0x100 __btrfs_mod_ref+0x1d7/0x2f0 walk_up_proc+0x11c/0x400 walk_up_tree+0xf0/0x180 btrfs_drop_snapshot+0x1c7/0x780 btrfs_clean_one_deleted_snapshot+0xfb/0x110 cleaner_kthread+0xd4/0x140 kthread+0x13a/0x150 ret_from_fork+0x1f/0x30 other info that might help us debug this: Chain exists of: btrfs-root-00 --> &caching_ctl->mutex --> &fs_info->commit_root_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->commit_root_sem); lock(&caching_ctl->mutex); lock(&fs_info->commit_root_sem); lock(btrfs-root-00); *** DEADLOCK *** 3 locks held by btrfs-cleaner/903: #0: ffff8e7fab628838 (&fs_info->cleaner_mutex){+.+.}-{3:3}, at: cleaner_kthread+0x6e/0x140 #1: ffff8e7faadac640 (sb_internal){.+.+}-{0:0}, at: start_transaction+0x40b/0x5c0 #2: ffff8e7fab628a88 (&fs_info->commit_root_sem){++++}-{3:3}, at: btrfs_find_all_roots+0x41/0x80 stack backtrace: CPU: 0 PID: 903 Comm: btrfs-cleaner Not tainted 5.9.0+ #102 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x8b/0xb0 check_noncircular+0xcf/0xf0 __lock_acquire+0x1167/0x2150 ? __bfs+0x42/0x210 lock_acquire+0xb9/0x3d0 ? __btrfs_tree_read_lock+0x32/0x170 down_read_nested+0x43/0x130 ? __btrfs_tree_read_lock+0x32/0x170 __btrfs_tree_read_lock+0x32/0x170 __btrfs_read_lock_root_node+0x3a/0x50 btrfs_search_slot+0x614/0x9d0 ? find_held_lock+0x2b/0x80 btrfs_find_root+0x35/0x1b0 ? do_raw_spin_unlock+0x4b/0xa0 btrfs_read_tree_root+0x61/0x120 btrfs_get_root_ref+0x14b/0x600 find_parent_nodes+0x3e6/0x1b30 btrfs_find_all_roots_safe+0xb4/0x130 btrfs_find_all_roots+0x60/0x80 btrfs_qgroup_trace_extent_post+0x27/0x40 btrfs_add_delayed_data_ref+0x3fd/0x460 btrfs_free_extent+0x42/0x100 __btrfs_mod_ref+0x1d7/0x2f0 walk_up_proc+0x11c/0x400 walk_up_tree+0xf0/0x180 btrfs_drop_snapshot+0x1c7/0x780 ? btrfs_clean_one_deleted_snapshot+0x73/0x110 btrfs_clean_one_deleted_snapshot+0xfb/0x110 cleaner_kthread+0xd4/0x140 ? btrfs_alloc_root+0x50/0x50 kthread+0x13a/0x150 ? kthread_create_worker_on_cpu+0x40/0x40 ret_from_fork+0x1f/0x30 BTRFS info (device sdb): disk space caching is enabled BTRFS info (device sdb): has skinny extents This happens because qgroups does a backref lookup when we create a delayed ref. From here it may have to look up a root from an indirect ref, which does a normal lookup on the tree_root, which takes the read lock on the tree_root nodes. To fix this we need to add a variant for looking up roots that searches the commit root of the tree_root. Then when we do the backref search using the commit root we are sure to not take any locks on the tree_root nodes. This gets rid of the lockdep splat when running btrfs/104. Reviewed-by: Filipe Manana Signed-off-by: Josef Bacik Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: check correct variable after allocation in btrfs_backref_iter_alloc

2020-08-10T17:50:54+00:00

The `if (!ret)` check will always be false and it may result in ret->path being dereferenced while it is a NULL pointer. Fixes: a37f232b7b65 ("btrfs: backref: introduce the skeleton of btrfs_backref_iter") CC: stable@vger.kernel.org # 5.8+ Reviewed-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: Boleyn Su Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: fix double free on ulist after backref resolution failure

2020-07-21T19:59:15+00:00

At btrfs_find_all_roots_safe() we allocate a ulist and set the **roots argument to point to it. However if later we fail due to an error returned by find_parent_nodes(), we free that ulist but leave a dangling pointer in the **roots argument. Upon receiving the error, a caller of this function can attempt to free the same ulist again, resulting in an invalid memory access. One such scenario is during qgroup accounting: btrfs_qgroup_account_extents() --> calls btrfs_find_all_roots() passes &new_roots (a stack allocated pointer) to btrfs_find_all_roots() --> btrfs_find_all_roots() just calls btrfs_find_all_roots_safe() passing &new_roots to it --> allocates ulist and assigns its address to **roots (which points to new_roots from btrfs_qgroup_account_extents()) --> find_parent_nodes() returns an error, so we free the ulist and leave **roots pointing to it after returning --> btrfs_qgroup_account_extents() sees btrfs_find_all_roots() returned an error and jumps to the label 'cleanup', which just tries to free again the same ulist Stack trace example: ------------[ cut here ]------------ BTRFS: tree first key check failed WARNING: CPU: 1 PID: 1763215 at fs/btrfs/disk-io.c:422 btrfs_verify_level_key+0xe0/0x180 [btrfs] Modules linked in: dm_snapshot dm_thin_pool (...) CPU: 1 PID: 1763215 Comm: fsstress Tainted: G W 5.8.0-rc3-btrfs-next-64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:btrfs_verify_level_key+0xe0/0x180 [btrfs] Code: 28 5b 5d (...) RSP: 0018:ffffb89b473779a0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff90397759bf08 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000027 RDI: 00000000ffffffff RBP: ffff9039a419c000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: ffffb89b43301000 R12: 000000000000005e R13: ffffb89b47377a2e R14: ffffb89b473779af R15: 0000000000000000 FS: 00007fc47e1e1000(0000) GS:ffff9039ac200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc47e1df000 CR3: 00000003d9e4e001 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: read_block_for_search+0xf6/0x350 [btrfs] btrfs_next_old_leaf+0x242/0x650 [btrfs] resolve_indirect_refs+0x7cf/0x9e0 [btrfs] find_parent_nodes+0x4ea/0x12c0 [btrfs] btrfs_find_all_roots_safe+0xbf/0x130 [btrfs] btrfs_qgroup_account_extents+0x9d/0x390 [btrfs] btrfs_commit_transaction+0x4f7/0xb20 [btrfs] btrfs_sync_file+0x3d4/0x4d0 [btrfs] do_fsync+0x38/0x70 __x64_sys_fdatasync+0x13/0x20 do_syscall_64+0x5c/0xe0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fc47e2d72e3 Code: Bad RIP value. RSP: 002b:00007fffa32098c8 EFLAGS: 00000246 ORIG_RAX: 000000000000004b RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fc47e2d72e3 RDX: 00007fffa3209830 RSI: 00007fffa3209830 RDI: 0000000000000003 RBP: 000000000000072e R08: 0000000000000001 R09: 0000000000000003 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000003e8 R13: 0000000051eb851f R14: 00007fffa3209970 R15: 00005607c4ac8b50 irq event stamp: 0 hardirqs last enabled at (0): [<0000000000000000>] 0x0 hardirqs last disabled at (0): [] copy_process+0x755/0x1eb0 softirqs last enabled at (0): [] copy_process+0x755/0x1eb0 softirqs last disabled at (0): [<0000000000000000>] 0x0 ---[ end trace 8639237550317b48 ]--- BTRFS error (device sdc): tree first key mismatch detected, bytenr=62324736 parent_transid=94 key expected=(262,108,1351680) has=(259,108,1921024) general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI CPU: 2 PID: 1763215 Comm: fsstress Tainted: G W 5.8.0-rc3-btrfs-next-64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:ulist_release+0x14/0x60 [btrfs] Code: c7 07 00 (...) RSP: 0018:ffffb89b47377d60 EFLAGS: 00010282 RAX: 6b6b6b6b6b6b6b6b RBX: ffff903959b56b90 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000270024 RDI: ffff9036e2adc840 RBP: ffff9036e2adc848 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9036e2adc840 R13: 0000000000000015 R14: ffff9039a419ccf8 R15: ffff90395d605840 FS: 00007fc47e1e1000(0000) GS:ffff9039ac600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8c1c0a51c8 CR3: 00000003d9e4e004 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ulist_free+0x13/0x20 [btrfs] btrfs_qgroup_account_extents+0xf3/0x390 [btrfs] btrfs_commit_transaction+0x4f7/0xb20 [btrfs] btrfs_sync_file+0x3d4/0x4d0 [btrfs] do_fsync+0x38/0x70 __x64_sys_fdatasync+0x13/0x20 do_syscall_64+0x5c/0xe0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fc47e2d72e3 Code: Bad RIP value. RSP: 002b:00007fffa32098c8 EFLAGS: 00000246 ORIG_RAX: 000000000000004b RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fc47e2d72e3 RDX: 00007fffa3209830 RSI: 00007fffa3209830 RDI: 0000000000000003 RBP: 000000000000072e R08: 0000000000000001 R09: 0000000000000003 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000003e8 R13: 0000000051eb851f R14: 00007fffa3209970 R15: 00005607c4ac8b50 Modules linked in: dm_snapshot dm_thin_pool (...) ---[ end trace 8639237550317b49 ]--- RIP: 0010:ulist_release+0x14/0x60 [btrfs] Code: c7 07 00 (...) RSP: 0018:ffffb89b47377d60 EFLAGS: 00010282 RAX: 6b6b6b6b6b6b6b6b RBX: ffff903959b56b90 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000270024 RDI: ffff9036e2adc840 RBP: ffff9036e2adc848 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9036e2adc840 R13: 0000000000000015 R14: ffff9039a419ccf8 R15: ffff90395d605840 FS: 00007fc47e1e1000(0000) GS:ffff9039ad200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6a776f7d40 CR3: 00000003d9e4e002 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Fix this by making btrfs_find_all_roots_safe() set *roots to NULL after it frees the ulist. Fixes: 8da6d5815c592b ("Btrfs: added btrfs_find_all_roots()") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: simplify root lookup by id

2020-05-25T09:25:36+00:00

The main function to lookup a root by its id btrfs_get_fs_root takes the whole key, while only using the objectid. The value of offset is preset to (u64)-1 but not actually used until btrfs_find_root that does the actual search. Switch btrfs_get_fs_root to use only objectid and remove all local variables that existed just for the lookup. The actual key for search is set up in btrfs_get_fs_root, reusing another key variable. Signed-off-by: David Sterba

btrfs: rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE

2020-05-25T09:25:35+00:00

The name BTRFS_ROOT_REF_COWS is not very clear about the meaning. In fact, that bit can only be set to those trees: - Subvolume roots - Data reloc root - Reloc roots for above roots All other trees won't get this bit set. So just by the result, it is obvious that, roots with this bit set can have tree blocks shared with other trees. Either shared by snapshots, or by reloc roots (an special snapshot created by relocation). This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to make it easier to understand, and update all comment mentioning "reference counted" to follow the rename. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: distinguish reloc and non-reloc use of indirect resolution

2020-05-25T09:25:22+00:00

For relocation tree detection, relocation backref cache uses btrfs_should_ignore_reloc_root() which uses relocation-specific checks like checking the DEAD_RELOC_ROOT bit. However for general purpose backref cache, we can rely on that check, as it's possible that relocation is also running. For generic purposed backref cache, we detect reloc root by SHARED_BLOCK_REF item. Only reloc root node has its parent bytenr pointing back to itself. And in that case, backref cache will mark the reloc root node useless, dropping any child orphan nodes. So only call btrfs_should_ignore_reloc_root() if the backref cache is for relocation. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: reloc: move error handling of build_backref_tree() to backref.c

2020-05-25T09:25:21+00:00

The error cleanup will be extracted as a new function, btrfs_backref_error_cleanup(), and moved to backref.c and exported for later usage. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move finish_upper_links()

2020-05-25T09:25:21+00:00

This the the 2nd major part of generic backref cache. Move it to backref.c so we can reuse it. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move handle_one_tree_block()

2020-05-25T09:25:21+00:00

This function is the major part of backref cache build process, move it to backref.c so we can reuse it later. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move backref_cache_cleanup()

2020-05-25T09:25:20+00:00

Since we're releasing all existing nodes/edges, other than cleanup the mess after error, "release" is a more proper naming here. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba