CVE-2026-90265

In the Linux kernel, the following vulnerability has been resolved:

btrfs: defrag: fix deadlock between defrag and delalloc space reservation

While running fsstress with autodefrag and flushoncommit, hit a deadlock
due to the fact that defrag reserves delalloc space while it's holding
dirty and locked folios, besides the extent range lock. The stack traces
are the following:

   [958.624] task:kworker/u50:3   state:D stack:0     pid:20365 tgid:20365 ppid:2      task_flags:0x4208060 flags:0x00080000
   [958.626] Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs]
   [958.627] Call Trace:
   [958.628]  <TASK>
   [958.628]  __schedule+0x4be/0x10f0
   [958.629]  ? preempt_count_add+0x69/0xa0
   [958.630]  schedule+0x26/0xd0
   [958.631]  wait_current_trans+0x102/0x160 [btrfs]
   [958.632]  ? __pfx_autoremove_wake_function+0x10/0x10
   [958.633]  start_transaction+0x374/0x900 [btrfs]
   [958.634]  btrfs_commit_current_transaction+0x1d/0x70 [btrfs]
   [958.635]  flush_space+0xca/0x5e0 [btrfs]
   [958.636]  ? _raw_spin_unlock+0x15/0x30
   [958.637]  ? btrfs_reduce_alloc_profile+0x8c/0x190 [btrfs]
   [958.639]  ? _raw_spin_unlock+0x15/0x30
   [958.640]  ? calc_available_free_space.isra.0+0x6f/0x110 [btrfs]
   [958.641]  do_async_reclaim_metadata_space+0x84/0x190 [btrfs]
   [958.642]  btrfs_async_reclaim_metadata_space+0x64/0x80 [btrfs]
   [958.644]  process_one_work+0x19d/0x3a0
   [958.644]  worker_thread+0x1c4/0x330
   [958.645]  ? __pfx_worker_thread+0x10/0x10
   [958.646]  kthread+0xfc/0x130
   [958.647]  ? __pfx_kthread+0x10/0x10
   [958.648]  ret_from_fork+0x1f7/0x2c0
   [958.648]  ? __pfx_kthread+0x10/0x10
   [958.649]  ret_from_fork_asm+0x1a/0x30
   [958.650]  </TASK>
   [958.651] task:kworker/u49:7   state:D stack:0     pid:52990 tgid:52990 ppid:2      task_flags:0x4208060 flags:0x00080000
   [958.653] Workqueue: writeback wb_workfn (flush-btrfs-334)
   [958.655] Call Trace:
   [958.655]  <TASK>
   [958.656]  __schedule+0x4be/0x10f0
   [958.657]  ? __blk_flush_plug+0xe9/0x140
   [958.658]  schedule+0x26/0xd0
   [958.658]  io_schedule+0x42/0x70
   [958.659]  folio_wait_bit_common+0x12b/0x330
   [958.660]  ? folio_wait_bit_common+0x100/0x330
   [958.662]  ? __pfx_wake_page_function+0x10/0x10
   [958.663]  extent_write_cache_pages+0x599/0x830 [btrfs]
   [958.664]  ? acpi_fwnode_get_reference_args+0x1fa/0x270
   [958.665]  btrfs_writepages+0x77/0x130 [btrfs]
   [958.666]  ? __pfx_end_bbio_data_write+0x10/0x10 [btrfs]
   [958.667]  do_writepages+0xc6/0x160
   [958.668]  __writeback_single_inode+0x42/0x310
   [958.669]  writeback_sb_inodes+0x231/0x570
   [958.670]  wb_writeback+0x8a/0x340
   [958.671]  wb_workfn+0xbf/0x450
   [958.672]  ? finish_task_switch.isra.0+0xc1/0x350
   [958.673]  process_one_work+0x19d/0x3a0
   [958.673]  worker_thread+0x1c4/0x330
   [958.674]  ? __pfx_worker_thread+0x10/0x10
   [958.675]  kthread+0xfc/0x130
   [958.676]  ? __pfx_kthread+0x10/0x10
   [958.676]  ret_from_fork+0x1f7/0x2c0
   [958.677]  ? __pfx_kthread+0x10/0x10
   [958.678]  ret_from_fork_asm+0x1a/0x30
   [958.679]  </TASK>
   [958.679] task:btrfs-cleaner   state:D stack:0     pid:296750 tgid:296750 ppid:2      task_flags:0x208040 flags:0x00080000
   [958.681] Call Trace:
   [958.682]  <TASK>
   [958.682]  __schedule+0x4be/0x10f0
   [958.683]  schedule+0x26/0xd0
   [958.684]  handle_reserve_ticket+0x1b9/0x2c0 [btrfs]
   [958.685]  ? __pfx_autoremove_wake_function+0x10/0x10
   [958.686]  reserve_bytes+0x283/0x4c0 [btrfs]
   [958.687]  btrfs_reserve_metadata_bytes+0x18/0xb0 [btrfs]
   [958.688]  btrfs_delalloc_reserve_metadata+0x121/0x320 [btrfs]
   [958.690]  btrfs_delalloc_reserve_space+0x46/0xb0 [btrfs]
   [958.691]  btrfs_defrag_file+0x903/0x1110 [btrfs]
   [958.692]  btrfs_run_defrag_inodes+0x334/0x430 [btrfs]
   [958.694]  cleaner_kthread+0x97/0x1c0 [btrfs]
   [958.694]  ? __pfx_cleaner_kthread+0x10/0x10 [btrfs]
   [958.696]  kthread+0xfc/0x130
   [958.696]  ? __pfx_kthread+0x10/0x10
   [958.697]  ret_
---truncated---