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BUG: KCSAN: data-race in __filemap_add_folio / file_write_and_wait_range

read-write to 0xffff88810ae6ced0 of 8 bytes by task 492 on cpu 1:
 __filemap_add_folio+0x379/0x6e0 mm/filemap.c:900
 filemap_add_folio+0x6b/0x150 mm/filemap.c:935
 __filemap_get_folio+0x50a/0x6d0 mm/filemap.c:1977
 pagecache_get_page+0x26/0xd0 mm/folio-compat.c:98
 grab_cache_page_write_begin+0x2a/0x30 mm/folio-compat.c:110
 block_write_begin+0x2e/0x170 fs/buffer.c:2098
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2456
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:230
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3772
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3900
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3932
 call_write_iter include/linux/fs.h:2189 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:646
 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+0x63/0xcd

read to 0xffff88810ae6ced0 of 8 bytes by task 529 on cpu 0:
 mapping_needs_writeback mm/filemap.c:624 [inline]
 file_write_and_wait_range+0x66/0x190 mm/filemap.c:776
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1132
 fat_file_fsync+0x48/0x100 fs/fat/file.c:191
 vfs_fsync_range fs/sync.c:188 [inline]
 vfs_fsync fs/sync.c:202 [inline]
 do_fsync fs/sync.c:212 [inline]
 __do_sys_fdatasync fs/sync.c:225 [inline]
 __se_sys_fdatasync fs/sync.c:223 [inline]
 __x64_sys_fdatasync+0x7a/0xd0 fs/sync.c:223
 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+0x63/0xcd

value changed: 0x0000000000000c69 -> 0x0000000000000c6a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 529 Comm: syz-executor.1 Tainted: G        W          6.2.0-rc3-syzkaller-00008-g1fe4fd6f5cad-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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