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BUG: KCSAN: data-race in __add_to_page_cache_locked / file_write_and_wait_range

write to 0xffff888105fcede0 of 8 bytes by task 26791 on cpu 0:
 __add_to_page_cache_locked+0x276/0x4f0 mm/filemap.c:931
 add_to_page_cache_lru+0xa0/0x1b0 mm/filemap.c:984
 page_cache_ra_unbounded+0x274/0x430 mm/readahead.c:222
 ondemand_readahead+0x58c/0x7c0
 page_cache_async_ra+0x17e/0x1a0 mm/readahead.c:609
 page_cache_async_readahead include/linux/pagemap.h:906 [inline]
 filemap_readahead mm/filemap.c:2520 [inline]
 filemap_get_pages mm/filemap.c:2561 [inline]
 filemap_read+0x4c0/0x1220 mm/filemap.c:2628
 generic_file_read_iter+0x75/0x2c0 mm/filemap.c:2779
 ext4_file_read_iter+0x1db/0x290
 call_read_iter include/linux/fs.h:2157 [inline]
 generic_file_splice_read+0x24f/0x330 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888105fcede0 of 8 bytes by task 26804 on cpu 1:
 mapping_needs_writeback mm/filemap.c:639 [inline]
 file_write_and_wait_range+0x4b/0x240 mm/filemap.c:809
 ext4_sync_file+0x105/0x670 fs/ext4/fsync.c:151
 vfs_fsync_range fs/sync.c:200 [inline]
 vfs_fsync fs/sync.c:214 [inline]
 do_fsync fs/sync.c:224 [inline]
 __do_sys_fdatasync fs/sync.c:237 [inline]
 __se_sys_fdatasync fs/sync.c:235 [inline]
 __x64_sys_fdatasync+0x7a/0xd0 fs/sync.c:235
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000000000026d -> 0x000000000000027c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26804 Comm: syz-executor.0 Not tainted 5.15.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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