syzbot

EXT4-fs (loop9): unmounting filesystem 00000000-0000-0000-0000-000000000000.
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BUG: KCSAN: data-race in folios_put_refs / need_mlock_drain

write to 0xffff888237d27248 of 1 bytes by task 25650 on cpu 1:
 folio_batch_reinit include/linux/folio_batch.h:50 [inline]
 folios_put_refs+0x28f/0x2d0 mm/swap.c:1002
 folios_put include/linux/mm.h:2149 [inline]
 mlock_folio_batch+0x1bae/0x1be0 mm/mlock.c:209
 mlock_folio+0x1d1/0x240 mm/mlock.c:259
 mlock_vma_folio mm/internal.h:1199 [inline]
 __folio_add_anon_rmap mm/rmap.c:1576 [inline]
 folio_add_anon_rmap_ptes+0x24e/0x250 mm/rmap.c:1599
 remove_migration_pte+0x7d9/0xbf0 mm/migrate.c:432
 rmap_walk_anon+0x280/0x430 mm/rmap.c:2999
 rmap_walk+0x8b/0xd0 mm/rmap.c:3104
 remove_migration_ptes mm/migrate.c:473 [inline]
 migrate_folio_move mm/migrate.c:1411 [inline]
 migrate_folios_move mm/migrate.c:1740 [inline]
 migrate_pages_batch+0x14cc/0x2010 mm/migrate.c:1996
 migrate_pages_sync mm/migrate.c:2026 [inline]
 migrate_pages+0x102e/0x1860 mm/migrate.c:2135
 do_mbind mm/mempolicy.c:1614 [inline]
 kernel_mbind mm/mempolicy.c:1757 [inline]
 __do_sys_mbind mm/mempolicy.c:1831 [inline]
 __se_sys_mbind+0xc98/0xdd0 mm/mempolicy.c:1827
 __x64_sys_mbind+0x78/0x90 mm/mempolicy.c:1827
 x64_sys_call+0x2b72/0x3020 arch/x86/include/generated/asm/syscalls_64.h:238
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d27248 of 1 bytes by task 25645 on cpu 0:
 folio_batch_count include/linux/folio_batch.h:56 [inline]
 need_mlock_drain+0x30/0x50 mm/mlock.c:235
 cpu_needs_drain mm/swap.c:792 [inline]
 __lru_add_drain_all+0x273/0x450 mm/swap.c:883
 lru_add_drain_all+0x10/0x20 mm/swap.c:899
 invalidate_bdev+0x47/0x70 block/bdev.c:101
 ext4_put_super+0x610/0x7b0 fs/ext4/super.c:1355
 generic_shutdown_super+0xee/0x220 fs/super.c:646
 kill_block_super+0x2a/0x70 fs/super.c:1725
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7492
 deactivate_locked_super+0x75/0x1c0 fs/super.c:476
 deactivate_super+0x97/0xa0 fs/super.c:509
 cleanup_mnt+0x2bb/0x330 fs/namespace.c:1312
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1319
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 25645 Comm: syz.9.5684 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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