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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

write to 0xffff8881005247f4 of 4 bytes by task 3696 on cpu 1:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark lib/xarray.c:900 [inline]
 __xa_set_mark+0x172/0x1a0 lib/xarray.c:2082
 __folio_mark_dirty+0x42c/0x520 mm/page-writeback.c:2689
 mark_buffer_dirty+0x120/0x1f0 fs/buffer.c:1116
 block_commit_write fs/buffer.c:2196 [inline]
 block_write_end+0x12d/0x210 fs/buffer.c:2272
 generic_write_end+0x56/0x150 fs/buffer.c:2286
 fat_write_end+0x4f/0x160 fs/fat/inode.c:245
 generic_perform_write+0x314/0x490 mm/filemap.c:4385
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4481
 generic_file_write_iter+0x77/0x1f0 mm/filemap.c:4507
 iter_file_splice_write+0x6a0/0xa60 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x156/0x280 fs/splice.c:1159
 splice_direct_to_actor+0x2f9/0x680 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881005247f4 of 4 bytes by task 3697 on cpu 0:
 xa_marked include/linux/xarray.h:424 [inline]
 xas_find_marked+0x602/0x650 lib/xarray.c:1483
 find_get_entry mm/filemap.c:2087 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2354
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 file_write_and_wait_range+0x20c/0x2f0 mm/filemap.c:789
 mmb_fsync_noflush+0x48/0x140 fs/buffer.c:652
 fat_file_fsync+0x98/0x110 fs/fat/file.c:193
 vfs_fsync_range+0xc5/0xe0 fs/sync.c:186
 generic_write_sync include/linux/fs.h:2666 [inline]
 generic_file_write_iter+0x1a3/0x1f0 mm/filemap.c:4511
 iter_file_splice_write+0x6a0/0xa60 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x156/0x280 fs/splice.c:1159
 splice_direct_to_actor+0x2f9/0x680 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x04000021 -> 0x0e000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3697 Comm: syz.3.53 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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