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BUG: KCSAN: data-race in __filemap_fdatawrite_range / xas_clear_mark

write to 0xffff88812064c77c of 4 bytes by task 6737 on cpu 0:
 xa_mark_clear lib/xarray.c:75 [inline]
 xas_clear_mark+0x16c/0x180 lib/xarray.c:918
 __test_set_page_writeback+0x3ae/0x480 mm/page-writeback.c:2808
 set_page_writeback include/linux/page-flags.h:567 [inline]
 __block_write_full_page+0x5a2/0x9d0 fs/buffer.c:1805
 block_write_full_page+0x172/0x1b0 fs/buffer.c:2980
 blkdev_writepage+0x20/0x30 fs/block_dev.c:627
 __writepage+0x32/0xc0 mm/page-writeback.c:2311
 write_cache_pages+0x4cb/0x820 mm/page-writeback.c:2246
 generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
 blkdev_writepages+0x19/0x20 fs/block_dev.c:1946
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 blkdev_fsync+0x42/0xa0 fs/block_dev.c:683
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2741 [inline]
 blkdev_write_iter+0x264/0x2a0 fs/block_dev.c:1907
 call_write_iter include/linux/fs.h:1877 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:721
 do_iter_write+0x112/0x4b0 fs/read_write.c:847
 vfs_iter_write+0x4c/0x70 fs/read_write.c:888
 iter_file_splice_write+0x41a/0x770 fs/splice.c:769
 do_splice_from fs/splice.c:865 [inline]
 direct_splice_actor+0x95/0x160 fs/splice.c:1035
 splice_direct_to_actor+0x365/0x660 fs/splice.c:990
 do_splice_direct+0xf2/0x170 fs/splice.c:1078
 do_sendfile+0x56a/0xba0 fs/read_write.c:1238
 __do_sys_sendfile64 fs/read_write.c:1299 [inline]
 __se_sys_sendfile64 fs/read_write.c:1285 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1285
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812064c77c of 4 bytes by task 6736 on cpu 1:
 xa_marked include/linux/xarray.h:416 [inline]
 mapping_tagged include/linux/fs.h:488 [inline]
 __filemap_fdatawrite_range+0x11c/0x1d0 mm/filemap.c:418
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 blkdev_fsync+0x42/0xa0 fs/block_dev.c:683
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2741 [inline]
 blkdev_write_iter+0x264/0x2a0 fs/block_dev.c:1907
 call_write_iter include/linux/fs.h:1877 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:721
 do_iter_write+0x112/0x4b0 fs/read_write.c:847
 vfs_iter_write+0x4c/0x70 fs/read_write.c:888
 iter_file_splice_write+0x41a/0x770 fs/splice.c:769
 do_splice_from fs/splice.c:865 [inline]
 direct_splice_actor+0x95/0x160 fs/splice.c:1035
 splice_direct_to_actor+0x365/0x660 fs/splice.c:990
 do_splice_direct+0xf2/0x170 fs/splice.c:1078
 do_sendfile+0x56a/0xba0 fs/read_write.c:1238
 __do_sys_sendfile64 fs/read_write.c:1299 [inline]
 __se_sys_sendfile64 fs/read_write.c:1285 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1285
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6736 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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