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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

write to 0xffff8881066e6014 of 4 bytes by task 16209 on cpu 0:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark lib/xarray.c:900 [inline]
 __xa_set_mark+0x192/0x1c0 lib/xarray.c:2076
 __folio_mark_dirty+0x3b8/0x4e0 mm/page-writeback.c:2767
 mark_buffer_dirty+0x134/0x230 fs/buffer.c:1196
 block_commit_write fs/buffer.c:2189 [inline]
 block_write_end+0x123/0x210 fs/buffer.c:2266
 generic_write_end+0x5c/0x160 fs/buffer.c:2280
 fat_write_end+0x4e/0x160 fs/fat/inode.c:242
 generic_perform_write+0x31e/0x4b0 mm/filemap.c:4124
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4220
 generic_file_write_iter+0x92/0x310 mm/filemap.c:4246
 iter_file_splice_write+0x5f2/0x980 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1158
 splice_direct_to_actor+0x305/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xd9/0x150 fs/splice.c:1227
 do_sendfile+0x40a/0x690 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x113/0x160 fs/read_write.c:1415
 x64_sys_call+0xfc3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881066e6014 of 4 bytes by task 16191 on cpu 1:
 xa_marked include/linux/xarray.h:424 [inline]
 xas_find_marked+0x614/0x660 lib/xarray.c:1483
 find_get_entry+0x5d/0x370 mm/filemap.c:2027
 filemap_get_folios_tag+0xa0/0x220 mm/filemap.c:2295
 __filemap_fdatawait_range mm/filemap.c:530 [inline]
 file_write_and_wait_range+0x206/0x2f0 mm/filemap.c:798
 __generic_file_fsync+0x46/0x140 fs/libfs.c:1525
 fat_file_fsync+0x46/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x116/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:2976 [inline]
 generic_file_write_iter+0x1cc/0x310 mm/filemap.c:4250
 iter_file_splice_write+0x5f2/0x980 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1158
 splice_direct_to_actor+0x305/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xd9/0x150 fs/splice.c:1227
 do_sendfile+0x40a/0x690 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x113/0x160 fs/read_write.c:1415
 x64_sys_call+0xfc3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 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: 1 UID: 0 PID: 16191 Comm: syz.6.4866 Not tainted 6.15.0-rc3-syzkaller-00019-gbc3372351d0c #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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