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BUG: KCSAN: data-race in __filemap_add_folio / sync_bdevs

read-write to 0xffff888100492b08 of 8 bytes by task 2963 on cpu 0:
 __filemap_add_folio+0x671/0x8b0 mm/filemap.c:919
 filemap_add_folio+0x1d3/0x350 mm/filemap.c:966
 __filemap_get_folio_mpol+0x326/0x680 mm/filemap.c:2021
 __filemap_get_folio include/linux/pagemap.h:763 [inline]
 grow_dev_folio fs/buffer.c:1047 [inline]
 grow_buffers fs/buffer.c:1113 [inline]
 __getblk_slow fs/buffer.c:1131 [inline]
 bdev_getblk+0x173/0x3f0 fs/buffer.c:1458
 __getblk include/linux/buffer_head.h:380 [inline]
 jbd2_journal_get_descriptor_buffer+0xce/0x210 fs/jbd2/journal.c:976
 jbd2_journal_commit_transaction+0xcc8/0x3420 fs/jbd2/commit.c:610
 kjournald2+0x22e/0x3e0 fs/jbd2/journal.c:201
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888100492b08 of 8 bytes by task 19578 on cpu 1:
 sync_bdevs+0xd3/0x260 block/bdev.c:1285
 ksys_sync fs/sync.c:105 [inline]
 __ia32_sys_sync+0x81/0xb0 fs/sync.c:111
 x64_sys_call+0x2f3a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000033d -> 0x000000000000033e

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19578 Comm: syz.0.4667 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================
loop0: detected capacity change from 0 to 256
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