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BUG: KCSAN: data-race in find_get_pages_range_tag / xas_set_mark

write to 0xffff8880b3aac8e8 of 8 bytes by task 20483 on cpu 1:
 instrument_write include/linux/instrumented.h:42 [inline]
 __test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:71 [inline]
 node_set_mark lib/xarray.c:93 [inline]
 xas_set_mark+0xc0/0x150 lib/xarray.c:879
 __xa_set_mark+0xdd/0x110 lib/xarray.c:1708
 __set_page_dirty+0x151/0x270 fs/buffer.c:618
 mark_buffer_dirty+0x26e/0x2b0 fs/buffer.c:1146
 __block_commit_write.isra.0+0x11d/0x170 fs/buffer.c:2075
 block_write_end+0x6d/0x140 fs/buffer.c:2153
 generic_write_end+0x8c/0x1f0 fs/buffer.c:2167
 fat_write_end+0x57/0x120 fs/fat/inode.c:250
 generic_perform_write+0x1d7/0x320 mm/filemap.c:3313
 __generic_file_write_iter+0x240/0x370 mm/filemap.c:3431
 generic_file_write_iter+0x294/0x38e mm/filemap.c:3463
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write+0x303/0x400 fs/read_write.c:484
 __vfs_write+0x9e/0xb0 fs/read_write.c:497
 vfs_write fs/read_write.c:559 [inline]
 vfs_write+0x189/0x380 fs/read_write.c:543
 ksys_write+0xc5/0x1a0 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x49/0x60 fs/read_write.c:621
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b3aac8e8 of 8 bytes by task 20504 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1625 [inline]
 xas_next_marked include/linux/xarray.h:1656 [inline]
 find_get_pages_range_tag+0x39a/0x670 mm/filemap.c:1911
 pagevec_lookup_range_tag+0x43/0x70 mm/swap.c:1078
 write_cache_pages+0x173/0xa10 mm/page-writeback.c:2195
 mpage_writepages+0xab/0x180 fs/mpage.c:730
 fat_writepages+0x2a/0x40 fs/fat/inode.c:205
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1bb/0x220 mm/filemap.c:421
 generic_fadvise+0x47b/0x490 mm/fadvise.c:115
 vfs_fadvise+0x8a/0x90 mm/fadvise.c:187
 ksys_fadvise64_64+0x5b/0xa0 mm/fadvise.c:201
 __do_sys_fadvise64 mm/fadvise.c:216 [inline]
 __se_sys_fadvise64 mm/fadvise.c:214 [inline]
 __x64_sys_fadvise64+0x5a/0x70 mm/fadvise.c:214
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20504 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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