syzbot

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BUG: KCSAN: data-race in __filemap_add_folio / filemap_write_and_wait_range

read-write to 0xffff88810048e978 of 8 bytes by task 21597 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:2016
 __filemap_get_folio include/linux/pagemap.h:774 [inline]
 grow_dev_folio fs/buffer.c:1048 [inline]
 grow_buffers fs/buffer.c:1114 [inline]
 __getblk_slow fs/buffer.c:1132 [inline]
 bdev_getblk+0x173/0x3f0 fs/buffer.c:1459
 sb_getblk_gfp include/linux/buffer_head.h:392 [inline]
 __ext4_sb_bread_gfp+0x44/0x170 fs/ext4/super.c:237
 ext4_sb_bread_unmovable fs/ext4/super.c:266 [inline]
 ext4_load_super fs/ext4/super.c:5120 [inline]
 __ext4_fill_super fs/ext4/super.c:5324 [inline]
 ext4_fill_super+0x491/0x37c0 fs/ext4/super.c:5793
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
 get_tree_bdev+0x1f/0x30 fs/super.c:1717
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5825
 vfs_get_tree+0x57/0x1d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3760 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3836
 path_mount+0x4d0/0xbc0 fs/namespace.c:4146
 do_mount fs/namespace.c:4159 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4325
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4325
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 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

read to 0xffff88810048e978 of 8 bytes by task 3002 on cpu 1:
 mapping_needs_writeback mm/filemap.c:634 [inline]
 filemap_write_and_wait_range+0x59/0x370 mm/filemap.c:683
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev block/bdev.c:276 [inline]
 bdev_release+0xeb/0x3d0 block/bdev.c:1142
 blkdev_release+0x15/0x20 block/fops.c:706
 __fput+0x29b/0x650 fs/file_table.c:469
 fput_close_sync+0xad/0x190 fs/file_table.c:574
 __do_sys_close fs/open.c:1509 [inline]
 __se_sys_close fs/open.c:1494 [inline]
 __x64_sys_close+0x55/0xf0 fs/open.c:1494
 x64_sys_call+0x275d/0x3020 arch/x86/include/generated/asm/syscalls_64.h:4
 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: 0x0000000000000000 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3002 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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