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Filipe Manana 3fdcfd91b9 btrfs: do not assert we found block group item when creating free space tree 
commit a5a51bf4e9 upstream.

Currently, when building a free space tree at populate_free_space_tree(),
if we are not using the block group tree feature, we always expect to find
block group items (either extent items or a block group item with key type
BTRFS_BLOCK_GROUP_ITEM_KEY) when we search the extent tree with
btrfs_search_slot_for_read(), so we assert that we found an item. However
this expectation is wrong since we can have a new block group created in
the current transaction which is still empty and for which we still have
not added the block group's item to the extent tree, in which case we do
not have any items in the extent tree associated to the block group.

The insertion of a new block group's block group item in the extent tree
happens at btrfs_create_pending_block_groups() when it calls the helper
insert_block_group_item(). This typically is done when a transaction
handle is released, committed or when running delayed refs (either as
part of a transaction commit or when serving tickets for space reservation
if we are low on free space).

So remove the assertion at populate_free_space_tree() even when the block
group tree feature is not enabled and update the comment to mention this
case.

Syzbot reported this with the following stack trace:

  BTRFS info (device loop3 state M): rebuilding free space tree
  assertion failed: ret == 0 :: 0, in fs/btrfs/free-space-tree.c:1115
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/free-space-tree.c:1115!
  Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
  CPU: 1 UID: 0 PID: 6352 Comm: syz.3.25 Not tainted syzkaller #0 PREEMPT(full)
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
  RIP: 0010:populate_free_space_tree+0x700/0x710 fs/btrfs/free-space-tree.c:1115
  Code: ff ff e8 d3 (...)
  RSP: 0018:ffffc9000430f780 EFLAGS: 00010246
  RAX: 0000000000000043 RBX: ffff88805b709630 RCX: fea61d0e2e79d000
  RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
  RBP: ffffc9000430f8b0 R08: ffffc9000430f4a7 R09: 1ffff92000861e94
  R10: dffffc0000000000 R11: fffff52000861e95 R12: 0000000000000001
  R13: 1ffff92000861f00 R14: dffffc0000000000 R15: 0000000000000000
  FS:  00007f424d9fe6c0(0000) GS:ffff888125afc000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fd78ad212c0 CR3: 0000000076d68000 CR4: 00000000003526f0
  Call Trace:
   <TASK>
   btrfs_rebuild_free_space_tree+0x1ba/0x6d0 fs/btrfs/free-space-tree.c:1364
   btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3062
   btrfs_remount_rw fs/btrfs/super.c:1334 [inline]
   btrfs_reconfigure+0xaed/0x2160 fs/btrfs/super.c:1559
   reconfigure_super+0x227/0x890 fs/super.c:1076
   do_remount fs/namespace.c:3279 [inline]
   path_mount+0xd1a/0xfe0 fs/namespace.c:4027
   do_mount fs/namespace.c:4048 [inline]
   __do_sys_mount fs/namespace.c:4236 [inline]
   __se_sys_mount+0x313/0x410 fs/namespace.c:4213
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   RIP: 0033:0x7f424e39066a
  Code: d8 64 89 02 (...)
  RSP: 002b:00007f424d9fde68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
  RAX: ffffffffffffffda RBX: 00007f424d9fdef0 RCX: 00007f424e39066a
  RDX: 0000200000000180 RSI: 0000200000000380 RDI: 0000000000000000
  RBP: 0000200000000180 R08: 00007f424d9fdef0 R09: 0000000000000020
  R10: 0000000000000020 R11: 0000000000000246 R12: 0000200000000380
  R13: 00007f424d9fdeb0 R14: 0000000000000000 R15: 00002000000002c0
   </TASK>
  Modules linked in:
  ---[ end trace 0000000000000000 ]---

Reported-by: syzbot+884dc4621377ba579a6f@syzkaller.appspotmail.com
Link: https://lore.kernel.org/linux-btrfs/68dc3dab.a00a0220.102ee.004e.GAE@google.com/
Fixes: a5ed918285 ("Btrfs: implement the free space B-tree")
CC: <stable@vger.kernel.org> # 6.1.x: 1961d20f6f: btrfs: fix assertion when building free space tree
CC: <stable@vger.kernel.org> # 6.1.x
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-23 16:20:20 +02:00
arch rust: cfi: only 64-bit arm and x86 support CFI_CLANG 2025-10-23 16:20:18 +02:00
block blk-crypto: fix missing blktrace bio split events 2025-10-19 16:33:48 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:33:42 +02:00
Documentation fs: Add 'initramfs_options' to set initramfs mount options 2025-10-19 16:34:06 +02:00
drivers r8152: add error handling in rtl8152_driver_init 2025-10-23 16:20:18 +02:00
fs btrfs: do not assert we found block group item when creating free space tree 2025-10-23 16:20:20 +02:00
include nfsd: unregister with rpcbind when deleting a transport 2025-10-19 16:34:03 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/waitid: always prune wait queue entry in io_waitid_wait() 2025-10-15 12:00:20 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel sched/fair: Block delayed tasks on throttled hierarchy during dequeue 2025-10-19 16:34:06 +02:00
lib lib/crypto/curve25519-hacl64: Disable KASAN with clang-17 and older 2025-10-19 16:34:00 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm slab: reset slab->obj_ext when freeing and it is OBJEXTS_ALLOC_FAIL 2025-10-23 16:20:18 +02:00
net mptcp: pm: in-kernel: usable client side with C-flag 2025-10-19 16:34:04 +02:00
rust rust: block: fix srctree/ links 2025-10-12 12:57:16 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:33:51 +02:00
sound ASoC: SOF: ipc4-pcm: fix start offset calculation for chain DMA 2025-10-19 16:34:07 +02:00
tools perf test stat: Avoid hybrid assumption when virtualized 2025-10-19 16:34:06 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.54 2025-10-19 16:34:07 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.