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BUG: KCSAN: data-race in __filemap_add_folio / file_write_and_wait_range

read-write to 0xffff88810864ddb0 of 8 bytes by task 19247 on cpu 1:
 __filemap_add_folio+0x492/0x700 mm/filemap.c:912
 filemap_add_folio+0x70/0x160 mm/filemap.c:947
 __filemap_get_folio+0x2f1/0x5b0 mm/filemap.c:1934
 pagecache_get_page+0x2a/0xa0 mm/folio-compat.c:93
 grab_cache_page_write_begin+0x2e/0x40 mm/folio-compat.c:103
 block_write_begin+0x31/0x170 fs/buffer.c:2209
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2567
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1d5/0x410 mm/filemap.c:3974
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4069
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4095
 call_write_iter include/linux/fs.h:2110 [inline]
 iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x970 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 x64_sys_call+0x2c67/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810864ddb0 of 8 bytes by task 19250 on cpu 0:
 mapping_needs_writeback mm/filemap.c:635 [inline]
 file_write_and_wait_range+0x6d/0x170 mm/filemap.c:787
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1473
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x122/0x140 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2795 [inline]
 generic_file_write_iter+0x191/0x1d0 mm/filemap.c:4099
 call_write_iter include/linux/fs.h:2110 [inline]
 iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x970 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
 x64_sys_call+0x2c67/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000001 -> 0x0000000000000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19250 Comm: syz-executor.4 Not tainted 6.9.0-rc4-syzkaller-00173-g3cdb45594619 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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