kernel/linux.git/fs/btrfs/relocation.c, branch v6.12.102

btrfs: free mapping node on duplicate reloc root insert

2026-08-03T09:17:08+00:00

[ Upstream commit 6a8269b6459ed870a8156c106a0f597383907872 ] __add_reloc_root() allocates a mapping_node before inserting it into rc->reloc_root_tree. If rb_simple_insert() finds an existing entry, it returns the existing rb_node and leaves the newly allocated node unlinked. The error path then returns -EEXIST without freeing the new node. Since the node was never inserted into reloc_root_tree, the later cleanup in put_reloc_control() cannot find it either. Free the newly allocated node before returning -EEXIST. The callers currently assert that -EEXIST should not happen, so this is a defensive cleanup for an unexpected duplicate insert path. If the path is ever reached, the local allocation should still be released. Fixes: 57a304cfd43b ("btrfs: do not panic in __add_reloc_root") Reviewed-by: Qu Wenruo Signed-off-by: Guanghui Yang <3497809730@qq.com> Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots()

2026-08-03T09:17:01+00:00

[ Upstream commit ce6050bafb4e33377dc17fcc357736bfc351180c ] If we have an unexpected reloc_root for our root, we jump to the out label but never drop the reference we obtained for root, resulting in a leak. Add a missing btrfs_put_root() call. Fixes: 24213fa46c70 ("btrfs: do proper error handling in merge_reloc_roots") Reviewed-by: Qu Wenruo Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: prevent use-after-free on folio private data in btrfs_subpage_clear_uptodate()

2026-02-06T15:55:50+00:00

This is a stable-only patch. The issue was inadvertently fixed in 6.17 [0] as part of a refactoring, but this patch serves as a minimal targeted fix for prior kernels. Users of filemap_lock_folio() need to guard against the situation where release_folio() has been invoked during reclaim but the folio was ultimately not removed from the page cache. This patch covers one location that was overlooked. After acquiring the folio, use set_folio_extent_mapped() to ensure the folio private state is valid. This is especially important in the subpage case, where the private field is an allocated struct containing bitmap and lock data. Without this protection, the race below is possible: [mm] page cache reclaim path [fs] relocation in subpage mode shrink_folio_list() folio_trylock() /* lock acquired */ filemap_release_folio() mapping->a_ops->release_folio() btrfs_release_folio() __btrfs_release_folio() clear_folio_extent_mapped() btrfs_detach_subpage() subpage = folio_detach_private(folio) btrfs_free_subpage(subpage) kfree(subpage) /* point A */ prealloc_file_extent_cluster() filemap_lock_folio() folio_try_get() /* inc refcount */ folio_lock() /* wait for lock */ if (...) ... else if (!mapping || !__remove_mapping(..)) /* * __remove_mapping() returns zero when * folio_ref_freeze(folio, refcount) fails /* point B */ */ goto keep_locked /* folio remains in cache */ keep_locked: folio_unlock(folio) /* lock released */ /* lock acquired */ btrfs_subpage_clear_uptodate() /* use-after-free */ subpage = folio_get_private(folio) [0] 4e346baee95f ("btrfs: reloc: unconditionally invalidate the page cache for each cluster") Fixes: 9d9ea1e68a05 ("btrfs: subpage: fix relocation potentially overwriting last page data") Cc: stable@vger.kernel.org # 6.10-6.16 Signed-off-by: JP Kobryn Reviewed-by: Qu Wenruo Signed-off-by: Greg Kroah-Hartman

btrfs: fix clearing of BTRFS_FS_RELOC_RUNNING if relocation already running

2025-10-23T14:20:19+00:00

commit 7e5a5983edda664e8e4bb20af17b80f5135c655c upstream. When starting relocation, at reloc_chunk_start(), if we happen to find the flag BTRFS_FS_RELOC_RUNNING is already set we return an error (-EINPROGRESS) to the callers, however the callers call reloc_chunk_end() which will clear the flag BTRFS_FS_RELOC_RUNNING, which is wrong since relocation was started by another task and still running. Finding the BTRFS_FS_RELOC_RUNNING flag already set is an unexpected scenario, but still our current behaviour is not correct. Fix this by never calling reloc_chunk_end() if reloc_chunk_start() has returned an error, which is what logically makes sense, since the general widespread pattern is to have end functions called only if the counterpart start functions succeeded. This requires changing reloc_chunk_start() to clear BTRFS_FS_RELOC_RUNNING if there's a pending cancel request. Fixes: 907d2710d727 ("btrfs: add cancellable chunk relocation support") CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Boris Burkov Reviewed-by: Johannes Thumshirn Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: do not allow relocation of partially dropped subvolumes

2025-08-20T16:30:54+00:00

commit 4289b494ac553e74e86fed1c66b2bf9530bc1082 upstream. [BUG] There is an internal report that balance triggered transaction abort, with the following call trace: item 85 key (594509824 169 0) itemoff 12599 itemsize 33 extent refs 1 gen 197740 flags 2 ref#0: tree block backref root 7 item 86 key (594558976 169 0) itemoff 12566 itemsize 33 extent refs 1 gen 197522 flags 2 ref#0: tree block backref root 7 ... BTRFS error (device loop0): extent item not found for insert, bytenr 594526208 num_bytes 16384 parent 449921024 root_objectid 934 owner 1 offset 0 BTRFS error (device loop0): failed to run delayed ref for logical 594526208 num_bytes 16384 type 182 action 1 ref_mod 1: -117 ------------[ cut here ]------------ BTRFS: Transaction aborted (error -117) WARNING: CPU: 1 PID: 6963 at ../fs/btrfs/extent-tree.c:2168 btrfs_run_delayed_refs+0xfa/0x110 [btrfs] And btrfs check doesn't report anything wrong related to the extent tree. [CAUSE] The cause is a little complex, firstly the extent tree indeed doesn't have the backref for 594526208. The extent tree only have the following two backrefs around that bytenr on-disk: item 65 key (594509824 METADATA_ITEM 0) itemoff 13880 itemsize 33 refs 1 gen 197740 flags TREE_BLOCK tree block skinny level 0 (176 0x7) tree block backref root CSUM_TREE item 66 key (594558976 METADATA_ITEM 0) itemoff 13847 itemsize 33 refs 1 gen 197522 flags TREE_BLOCK tree block skinny level 0 (176 0x7) tree block backref root CSUM_TREE But the such missing backref item is not an corruption on disk, as the offending delayed ref belongs to subvolume 934, and that subvolume is being dropped: item 0 key (934 ROOT_ITEM 198229) itemoff 15844 itemsize 439 generation 198229 root_dirid 256 bytenr 10741039104 byte_limit 0 bytes_used 345571328 last_snapshot 198229 flags 0x1000000000001(RDONLY) refs 0 drop_progress key (206324 EXTENT_DATA 2711650304) drop_level 2 level 2 generation_v2 198229 And that offending tree block 594526208 is inside the dropped range of that subvolume. That explains why there is no backref item for that bytenr and why btrfs check is not reporting anything wrong. But this also shows another problem, as btrfs will do all the orphan subvolume cleanup at a read-write mount. So half-dropped subvolume should not exist after an RW mount, and balance itself is also exclusive to subvolume cleanup, meaning we shouldn't hit a subvolume half-dropped during relocation. The root cause is, there is no orphan item for this subvolume. In fact there are 5 subvolumes from around 2021 that have the same problem. It looks like the original report has some older kernels running, and caused those zombie subvolumes. Thankfully upstream commit 8d488a8c7ba2 ("btrfs: fix subvolume/snapshot deletion not triggered on mount") has long fixed the bug. [ENHANCEMENT] For repairing such old fs, btrfs-progs will be enhanced. Considering how delayed the problem will show up (at run delayed ref time) and at that time we have to abort transaction already, it is too late. Instead here we reject any half-dropped subvolume for reloc tree at the earliest time, preventing confusion and extra time wasted on debugging similar bugs. CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: convert BUG_ON in btrfs_reloc_cow_block() to proper error handling

2025-02-17T09:04:43+00:00

[ Upstream commit 6a4730b325aaa48f7a5d5ba97aff0a955e2d9cec ] This BUG_ON is meant to catch backref cache problems, but these can arise from either bugs in the backref cache or corruption in the extent tree. Fix it to be a proper error. Reviewed-by: Boris Burkov Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: check folio mapping after unlock in relocate_one_folio()

2025-01-02T09:34:25+00:00

commit 3e74859ee35edc33a022c3f3971df066ea0ca6b9 upstream. When we call btrfs_read_folio() to bring a folio uptodate, we unlock the folio. The result of that is that a different thread can modify the mapping (like remove it with invalidate) before we call folio_lock(). This results in an invalid page and we need to try again. In particular, if we are relocating concurrently with aborting a transaction, this can result in a crash like the following: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: 0000 [#1] SMP CPU: 76 PID: 1411631 Comm: kworker/u322:5 Workqueue: events_unbound btrfs_reclaim_bgs_work RIP: 0010:set_page_extent_mapped+0x20/0xb0 RSP: 0018:ffffc900516a7be8 EFLAGS: 00010246 RAX: ffffea009e851d08 RBX: ffffea009e0b1880 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffc900516a7b90 RDI: ffffea009e0b1880 RBP: 0000000003573000 R08: 0000000000000001 R09: ffff88c07fd2f3f0 R10: 0000000000000000 R11: 0000194754b575be R12: 0000000003572000 R13: 0000000003572fff R14: 0000000000100cca R15: 0000000005582fff FS: 0000000000000000(0000) GS:ffff88c07fd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000407d00f002 CR4: 00000000007706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: ? __die+0x78/0xc0 ? page_fault_oops+0x2a8/0x3a0 ? __switch_to+0x133/0x530 ? wq_worker_running+0xa/0x40 ? exc_page_fault+0x63/0x130 ? asm_exc_page_fault+0x22/0x30 ? set_page_extent_mapped+0x20/0xb0 relocate_file_extent_cluster+0x1a7/0x940 relocate_data_extent+0xaf/0x120 relocate_block_group+0x20f/0x480 btrfs_relocate_block_group+0x152/0x320 btrfs_relocate_chunk+0x3d/0x120 btrfs_reclaim_bgs_work+0x2ae/0x4e0 process_scheduled_works+0x184/0x370 worker_thread+0xc6/0x3e0 ? blk_add_timer+0xb0/0xb0 kthread+0xae/0xe0 ? flush_tlb_kernel_range+0x90/0x90 ret_from_fork+0x2f/0x40 ? flush_tlb_kernel_range+0x90/0x90 ret_from_fork_asm+0x11/0x20 This occurs because cleanup_one_transaction() calls destroy_delalloc_inodes() which calls invalidate_inode_pages2() which takes the folio_lock before setting mapping to NULL. We fail to check this, and subsequently call set_extent_mapping(), which assumes that mapping != NULL (in fact it asserts that in debug mode) Note that the "fixes" patch here is not the one that introduced the race (the very first iteration of this code from 2009) but a more recent change that made this particular crash happen in practice. Fixes: e7f1326cc24e ("btrfs: set page extent mapped after read_folio in relocate_one_page") CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Qu Wenruo Signed-off-by: Boris Burkov Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: fix a NULL pointer dereference when failed to start a new trasacntion

2024-10-01T17:22:37+00:00

[BUG] Syzbot reported a NULL pointer dereference with the following crash: FAULT_INJECTION: forcing a failure. start_transaction+0x830/0x1670 fs/btrfs/transaction.c:676 prepare_to_relocate+0x31f/0x4c0 fs/btrfs/relocation.c:3642 relocate_block_group+0x169/0xd20 fs/btrfs/relocation.c:3678 ... BTRFS info (device loop0): balance: ended with status: -12 Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cc: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000660-0x0000000000000667] RIP: 0010:btrfs_update_reloc_root+0x362/0xa80 fs/btrfs/relocation.c:926 Call Trace: commit_fs_roots+0x2ee/0x720 fs/btrfs/transaction.c:1496 btrfs_commit_transaction+0xfaf/0x3740 fs/btrfs/transaction.c:2430 del_balance_item fs/btrfs/volumes.c:3678 [inline] reset_balance_state+0x25e/0x3c0 fs/btrfs/volumes.c:3742 btrfs_balance+0xead/0x10c0 fs/btrfs/volumes.c:4574 btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3673 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f [CAUSE] The allocation failure happens at the start_transaction() inside prepare_to_relocate(), and during the error handling we call unset_reloc_control(), which makes fs_info->balance_ctl to be NULL. Then we continue the error path cleanup in btrfs_balance() by calling reset_balance_state() which will call del_balance_item() to fully delete the balance item in the root tree. However during the small window between set_reloc_contrl() and unset_reloc_control(), we can have a subvolume tree update and created a reloc_root for that subvolume. Then we go into the final btrfs_commit_transaction() of del_balance_item(), and into btrfs_update_reloc_root() inside commit_fs_roots(). That function checks if fs_info->reloc_ctl is in the merge_reloc_tree stage, but since fs_info->reloc_ctl is NULL, it results a NULL pointer dereference. [FIX] Just add extra check on fs_info->reloc_ctl inside btrfs_update_reloc_root(), before checking fs_info->reloc_ctl->merge_reloc_tree. That DEAD_RELOC_TREE handling is to prevent further modification to the reloc tree during merge stage, but since there is no reloc_ctl at all, we do not need to bother that. Reported-by: syzbot+283673dbc38527ef9f3d@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/66f6bfa7.050a0220.38ace9.0019.GAE@google.com/ CC: stable@vger.kernel.org # 4.19+ Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: drop the backref cache during relocation if we commit

2024-10-01T17:10:26+00:00

Since the inception of relocation we have maintained the backref cache across transaction commits, updating the backref cache with the new bytenr whenever we COWed blocks that were in the cache, and then updating their bytenr once we detected a transaction id change. This works as long as we're only ever modifying blocks, not changing the structure of the tree. However relocation does in fact change the structure of the tree. For example, if we are relocating a data extent, we will look up all the leaves that point to this data extent. We will then call do_relocation() on each of these leaves, which will COW down to the leaf and then update the file extent location. But, a key feature of do_relocation() is the pending list. This is all the pending nodes that we modified when we updated the file extent item. We will then process all of these blocks via finish_pending_nodes, which calls do_relocation() on all of the nodes that led up to that leaf. The purpose of this is to make sure we don't break sharing unless we absolutely have to. Consider the case that we have 3 snapshots that all point to this leaf through the same nodes, the initial COW would have created a whole new path. If we did this for all 3 snapshots we would end up with 3x the number of nodes we had originally. To avoid this we will cycle through each of the snapshots that point to each of these nodes and update their pointers to point at the new nodes. Once we update the pointer to the new node we will drop the node we removed the link for and all of its children via btrfs_drop_subtree(). This is essentially just btrfs_drop_snapshot(), but for an arbitrary point in the snapshot. The problem with this is that we will never reflect this in the backref cache. If we do this btrfs_drop_snapshot() for a node that is in the backref tree, we will leave the node in the backref tree. This becomes a problem when we change the transid, as now the backref cache has entire subtrees that no longer exist, but exist as if they still are pointed to by the same roots. In the best case scenario you end up with "adding refs to an existing tree ref" errors from insert_inline_extent_backref(), where we attempt to link in nodes on roots that are no longer valid. Worst case you will double free some random block and re-use it when there's still references to the block. This is extremely subtle, and the consequences are quite bad. There isn't a way to make sure our backref cache is consistent between transid's. In order to fix this we need to simply evict the entire backref cache anytime we cross transid's. This reduces performance in that we have to rebuild this backref cache every time we change transid's, but fixes the bug. This has existed since relocation was added, and is a pretty critical bug. There's a lot more cleanup that can be done now that this functionality is going away, but this patch is as small as possible in order to fix the problem and make it easy for us to backport it to all the kernels it needs to be backported to. Followup series will dismantle more of this code and simplify relocation drastically to remove this functionality. We have a reproducer that reproduced the corruption within a few minutes of running. With this patch it survives several iterations/hours of running the reproducer. Fixes: 3fd0a5585eb9 ("Btrfs: Metadata ENOSPC handling for balance") CC: stable@vger.kernel.org Reviewed-by: Boris Burkov Signed-off-by: Josef Bacik Signed-off-by: David Sterba

btrfs: don't readahead the relocation inode on RST

2024-09-10T14:51:17+00:00

On relocation we're doing readahead on the relocation inode, but if the filesystem is backed by a RAID stripe tree we can get ENOENT (e.g. due to preallocated extents not being mapped in the RST) from the lookup. But readahead doesn't handle the error and submits invalid reads to the device, causing an assertion in the scatter-gather list code: BTRFS info (device nvme1n1): balance: start -d -m -s BTRFS info (device nvme1n1): relocating block group 6480920576 flags data|raid0 BTRFS error (device nvme1n1): cannot find raid-stripe for logical [6481928192, 6481969152] devid 2, profile raid0 ------------[ cut here ]------------ kernel BUG at include/linux/scatterlist.h:115! Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 1012 Comm: btrfs Not tainted 6.10.0-rc7+ #567 RIP: 0010:__blk_rq_map_sg+0x339/0x4a0 RSP: 0018:ffffc90001a43820 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffea00045d4802 RDX: 0000000117520000 RSI: 0000000000000000 RDI: ffff8881027d1000 RBP: 0000000000003000 R08: ffffea00045d4902 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000001000 R12: ffff8881003d10b8 R13: ffffc90001a438f0 R14: 0000000000000000 R15: 0000000000003000 FS: 00007fcc048a6900(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000002cd11000 CR3: 00000001109ea001 CR4: 0000000000370eb0 Call Trace: ? __die_body.cold+0x14/0x25 ? die+0x2e/0x50 ? do_trap+0xca/0x110 ? do_error_trap+0x65/0x80 ? __blk_rq_map_sg+0x339/0x4a0 ? exc_invalid_op+0x50/0x70 ? __blk_rq_map_sg+0x339/0x4a0 ? asm_exc_invalid_op+0x1a/0x20 ? __blk_rq_map_sg+0x339/0x4a0 nvme_prep_rq.part.0+0x9d/0x770 nvme_queue_rq+0x7d/0x1e0 __blk_mq_issue_directly+0x2a/0x90 ? blk_mq_get_budget_and_tag+0x61/0x90 blk_mq_try_issue_list_directly+0x56/0xf0 blk_mq_flush_plug_list.part.0+0x52b/0x5d0 __blk_flush_plug+0xc6/0x110 blk_finish_plug+0x28/0x40 read_pages+0x160/0x1c0 page_cache_ra_unbounded+0x109/0x180 relocate_file_extent_cluster+0x611/0x6a0 ? btrfs_search_slot+0xba4/0xd20 ? balance_dirty_pages_ratelimited_flags+0x26/0xb00 relocate_data_extent.constprop.0+0x134/0x160 relocate_block_group+0x3f2/0x500 btrfs_relocate_block_group+0x250/0x430 btrfs_relocate_chunk+0x3f/0x130 btrfs_balance+0x71b/0xef0 ? kmalloc_trace_noprof+0x13b/0x280 btrfs_ioctl+0x2c2e/0x3030 ? kvfree_call_rcu+0x1e6/0x340 ? list_lru_add_obj+0x66/0x80 ? mntput_no_expire+0x3a/0x220 __x64_sys_ioctl+0x96/0xc0 do_syscall_64+0x54/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fcc04514f9b Code: Unable to access opcode bytes at 0x7fcc04514f71. RSP: 002b:00007ffeba923370 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fcc04514f9b RDX: 00007ffeba923460 RSI: 00000000c4009420 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000013 R09: 0000000000000001 R10: 00007fcc043fbba8 R11: 0000000000000246 R12: 00007ffeba924fc5 R13: 00007ffeba923460 R14: 0000000000000002 R15: 00000000004d4bb0 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:__blk_rq_map_sg+0x339/0x4a0 RSP: 0018:ffffc90001a43820 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffea00045d4802 RDX: 0000000117520000 RSI: 0000000000000000 RDI: ffff8881027d1000 RBP: 0000000000003000 R08: ffffea00045d4902 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000001000 R12: ffff8881003d10b8 R13: ffffc90001a438f0 R14: 0000000000000000 R15: 0000000000003000 FS: 00007fcc048a6900(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fcc04514f71 CR3: 00000001109ea001 CR4: 0000000000370eb0 Kernel panic - not syncing: Fatal exception Kernel Offset: disabled ---[ end Kernel panic - not syncing: Fatal exception ]--- So in case of a relocation on a RAID stripe-tree based file system, skip the readahead. Reviewed-by: Josef Bacik Reviewed-by: Qu Wenruo Signed-off-by: Johannes Thumshirn Reviewed-by: David Sterba Signed-off-by: David Sterba