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BUG: KCSAN: data-race in __filemap_add_folio / file_write_and_wait_range

read-write to 0xffff88812f922c10 of 8 bytes by task 3846 on cpu 0:
 __filemap_add_folio+0x2d9/0x7f0 mm/filemap.c:904
 filemap_add_folio+0x6b/0x150 mm/filemap.c:959
 __filemap_get_folio+0x4bd/0x680 mm/filemap.c:2003
 pagecache_get_page+0x26/0x190 mm/folio-compat.c:126
 grab_cache_page_write_begin+0x2a/0x30 mm/folio-compat.c:138
 block_write_begin+0x2e/0x170 fs/buffer.c:2113
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2468
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3779
 __generic_file_write_iter+0x172/0x280 mm/filemap.c:3875
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3939
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:868
 vfs_iter_write+0x4c/0x70 fs/read_write.c:909
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1262
 __do_sys_sendfile64 fs/read_write.c:1327 [inline]
 __se_sys_sendfile64 fs/read_write.c:1313 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1313
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

read to 0xffff88812f922c10 of 8 bytes by task 3841 on cpu 1:
 mapping_needs_writeback mm/filemap.c:627 [inline]
 file_write_and_wait_range+0x4b/0x170 mm/filemap.c:778
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1115
 fat_file_fsync+0x48/0x100 fs/fat/file.c:190
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2731 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3943
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:868
 vfs_iter_write+0x4c/0x70 fs/read_write.c:909
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1262
 __do_sys_sendfile64 fs/read_write.c:1327 [inline]
 __se_sys_sendfile64 fs/read_write.c:1313 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1313
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

value changed: 0x00000000000000e1 -> 0x00000000000000e2

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3841 Comm: syz-executor.3 Not tainted 5.19.0-rc3-syzkaller-00390-g82708bb1eb9e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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