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BUG: KCSAN: data-race in find_get_pages_range_tag / xas_clear_mark

write to 0xffff88810dba6d78 of 8 bytes by task 9884 on cpu 1:
 instrument_write include/linux/instrumented.h:42 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:79 [inline]
 __test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:109 [inline]
 node_clear_mark lib/xarray.c:100 [inline]
 xas_clear_mark+0xa1/0x180 lib/xarray.c:911
 __test_set_page_writeback+0x3db/0x4f0 mm/page-writeback.c:2802
 set_page_writeback include/linux/page-flags.h:562 [inline]
 __mpage_writepage+0xf47/0x1110 fs/mpage.c:644
 write_cache_pages+0x4dc/0x830 mm/page-writeback.c:2246
 mpage_writepages+0x6d/0x120 fs/mpage.c:714
 fat_writepages+0x20/0x30 fs/fat/inode.c:205
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:763
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1078
 fat_file_fsync+0x48/0x100 fs/fat/file.c:190
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2843 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3668
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810dba6d78 of 8 bytes by task 9898 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1660 [inline]
 xas_next_marked include/linux/xarray.h:1691 [inline]
 find_get_pages_range_tag+0x35c/0x600 mm/filemap.c:2109
 pagevec_lookup_range_tag+0x37/0x50 mm/swap.c:1122
 write_cache_pages+0x1f8/0x830 mm/page-writeback.c:2203
 mpage_writepages+0x6d/0x120 fs/mpage.c:714
 fat_writepages+0x20/0x30 fs/fat/inode.c:205
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:424
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:763
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1078
 fat_file_fsync+0x48/0x100 fs/fat/file.c:190
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2843 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3668
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9898 Comm: syz-executor.4 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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