[syzbot] [bcachefs?] WARNING in bch2_btree_node_mem_alloc (2)

[syzbot <syzbot+6f91a1a3e34f980bb72c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    c435a4f487e8 Merge tag 'riscv-for-linus-6.16-rc5' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13c4cf70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b29b1a0d7330d4a8
dashboard link: https://syzkaller.appspot.com/bug?extid=6f91a1a3e34f980bb72c
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c435a4f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3a184d1ad283/vmlinux-c435a4f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/db5931917c56/bzImage-c435a4f4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6f91a1a3e34f980bb72c@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
bcachefs (loop0): starting version 1.519: (unknown version) opts=metadata_checksum=none,data_checksum=none,checksum_err_retry_nr=0,compression=lz4,nopromote_whole_extents,fsck,norecovery,nojournal_transaction_names,allocator_stuck_timeout=3,version_upgrade=incompatible
  allowing incompatible features above 0.0: (unknown version)
  features: lz4,new_siphash,inline_data,new_extent_overwrite,btree_ptr_v2,new_varint,journal_no_flush,alloc_v2,extents_across_btree_nodes
bcachefs (loop0): Using encoding defined by superblock: utf8-12.1.0
bcachefs (loop0): invalid bkey in superblock btree=extents level=1: u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq c6c25c03258c59c5 written 16 min_key 360287970189639680:0:0 durability: 0 (invalid extent entry 000000000001b000)
  invalid extent entry type (got 12, max 7), deleting
bcachefs (loop0): recovering from clean shutdown, journal seq 10
bcachefs (loop0): Version downgrade required:
bcachefs (loop0): Version upgrade required:
Version upgrade from 0.24: unwritten_extents to 1.519: (unknown version) incomplete
Doing incompatible version upgrade from 0.24: unwritten_extents to 1.28: inode_has_case_insensitive
  running recovery passes: check_allocations,check_alloc_info,check_lrus,check_btree_backpointers,check_backpointers_to_extents,check_extents_to_backpointers,check_alloc_to_lru_refs,bucket_gens_init,check_snapshot_trees,check_snapshots,check_subvols,check_subvol_children,delete_dead_snapshots,check_inodes,check_extents,check_indirect_extents,check_dirents,check_xattrs,check_root,check_unreachable_inodes,check_subvolume_structure,check_directory_structure,check_nlinks,check_rebalance_work,set_fs_needs_rebalance
bcachefs (loop0): Now allowing incompatible features up to 1.28: inode_has_case_insensitive, previously allowed up to 0.0: (unknown version)
bcachefs (loop0): error reading btree root btree=dirents level=0: btree_node_read_error, fixing
bcachefs (loop0): invalid bkey in btree_node btree=alloc level=0: u64s 11 type xattr POS_MIN len 0 ver 0: (type 1): 
  invalid key type for btree alloc (xattr), deleting
bcachefs (loop0): error reading btree root btree=alloc level=0: btree_node_read_error, fixing
bcachefs (loop0): btree node read error at btree snapshots level 0/0
  u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq ebb8d5a9e3463bdb written 16 min_key 0:262144:0 durability: 1 ptr: 0:32:0 gen 0
  loop0 node offset 0/16: incorrect min_key: got POS_MIN should be 0:262144:0
  flagging btree snapshots lost data
  running recovery pass reconstruct_snapshots (21), currently at recovery_pass_empty (0)
  ret btree_node_read_validate_error
bcachefs (loop0): error reading btree root btree=snapshots level=0: btree_node_read_error, fixing
bcachefs (loop0): error reading btree root btree=freespace level=0: btree_node_read_error, fixing
bcachefs (loop0): check_topology...
bcachefs (loop0): btree root dirents unreadable, must recover from scan
bcachefs (loop0): running recovery pass scan_for_btree_nodes (1), currently at check_topology (2) - rewinding
bcachefs (loop0): bch2_check_root(): error restart_recovery
bcachefs (loop0): scan_for_btree_nodes...
bcachefs (loop0): btree node scan found 7 nodes after overwrites
 done
bcachefs (loop0): check_topology...
bcachefs (loop0): btree root dirents unreadable, must recover from scan
bcachefs (loop0): bch2_get_scanned_nodes(): recovery btree=dirents level=0 POS_MIN - SPOS_MAX
bcachefs (loop0): bch2_get_scanned_nodes(): recovering u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 9aa2895aefce4bdf written 24 min_key POS_MIN durability: 1 ptr: 0:41:0 gen 0
bcachefs (loop0): empty interior btree node at btree=dirents level=1
  u64s 5 type btree_ptr SPOS_MAX len 0 ver 0, fixing
bcachefs (loop0): bch2_btree_repair_topology_recurse(): error ECHILD
bcachefs (loop0): empty btree root dirents
bcachefs (loop0): btree root snapshots unreadable, must recover from scan
------------[ cut here ]------------
btree cache cannibalize failed
WARNING: CPU: 0 PID: 5351 at fs/bcachefs/btree_cache.c:771 btree_node_cannibalize fs/bcachefs/btree_cache.c:771 [inline]
WARNING: CPU: 0 PID: 5351 at fs/bcachefs/btree_cache.c:771 bch2_btree_node_mem_alloc+0x1015/0x1820 fs/bcachefs/btree_cache.c:871
Modules linked in:
CPU: 0 UID: 0 PID: 5351 Comm: syz.0.0 Not tainted 6.16.0-rc4-syzkaller-00286-gc435a4f487e8 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:btree_node_cannibalize fs/bcachefs/btree_cache.c:771 [inline]
RIP: 0010:bch2_btree_node_mem_alloc+0x1015/0x1820 fs/bcachefs/btree_cache.c:871
Code: d2 e8 8f ca 74 fd 2e 2e 2e 31 c0 e9 a6 fe ff ff e8 c0 ae a2 fd c6 05 4d 27 6e 0b 01 90 48 c7 c7 c0 24 d3 8b e8 3c 57 66 fd 90 <0f> 0b 90 90 eb c3 e8 a0 ae a2 fd eb 05 e8 99 ae a2 fd 49 8d bf b0
RSP: 0018:ffffc9000d4b6d40 EFLAGS: 00010246
RAX: 35dc07f7034c9600 RBX: ffff888059d80000 RCX: 0000000000100000
RDX: ffffc9000f7e1000 RSI: 00000000000fffff RDI: 0000000000100000
RBP: ffff888059d81ce8 R08: ffff88801fc24293 R09: 1ffff11003f84852
R10: dffffc0000000000 R11: ffffed1003f84853 R12: ffff888059cfc800
R13: ffff888059cfca28 R14: ffff888059d81cf0 R15: dffffc0000000000
FS:  00007f3575bd46c0(0000) GS:ffff88808d21c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558c3af5f8 CR3: 0000000011c4d000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bch2_btree_root_alloc_fake_trans+0x141/0xb00 fs/bcachefs/btree_update_interior.c:2655
 bch2_check_root fs/bcachefs/btree_gc.c:566 [inline]
 bch2_check_topology+0x390/0xe00 fs/bcachefs/btree_gc.c:594
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x395/0x1010 fs/bcachefs/recovery_passes.c:539
 bch2_run_recovery_passes+0x184/0x210 fs/bcachefs/recovery_passes.c:610
 bch2_fs_recovery+0x2690/0x3a50 fs/bcachefs/recovery.c:1005
 bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1213
 bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902
 do_mount fs/namespace.c:4239 [inline]
 __do_sys_mount fs/namespace.c:4450 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35797900ca
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3575bd3e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f3575bd3ef0 RCX: 00007f35797900ca
RDX: 00002000000000c0 RSI: 0000200000000100 RDI: 00007f3575bd3eb0
RBP: 00002000000000c0 R08: 00007f3575bd3ef0 R09: 000000000000001e
R10: 000000000000001e R11: 0000000000000246 R12: 0000200000000100
R13: 00007f3575bd3eb0 R14: 0000000000005aa7 R15: 00002000000001c0
 </TASK>


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