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BUG: KCSAN: data-race in __filemap_add_folio / ext4_writepages

write to 0xffff888138395300 of 8 bytes by task 9892 on cpu 0:
 __filemap_add_folio+0x256/0x4d0 mm/filemap.c:931
 filemap_add_folio+0x6b/0x150 mm/filemap.c:984
 __filemap_get_folio+0x4c4/0x690 mm/filemap.c:1946
 pagecache_get_page+0x26/0xe0 mm/folio-compat.c:125
 grab_cache_page_write_begin+0x3f/0x50 mm/folio-compat.c:139
 ext4_da_write_begin+0x323/0x590 fs/ext4/inode.c:2961
 generic_perform_write+0x1c8/0x400 mm/filemap.c:3746
 ext4_buffered_write_iter+0x25b/0x380 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x1200
 call_write_iter include/linux/fs.h:2161 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x7f5/0x950 fs/read_write.c:590
 ksys_write+0xd9/0x190 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:652
 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 0xffff888138395300 of 8 bytes by task 10130 on cpu 1:
 ext4_writepages+0x16d/0x1e80 fs/ext4/inode.c:2666
 do_writepages+0x1cb/0x320 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:399 [inline]
 __filemap_fdatawrite_range+0xdf/0x110 mm/filemap.c:432
 generic_fadvise+0x1dc/0x430 mm/fadvise.c:113
 vfs_fadvise mm/fadvise.c:186 [inline]
 ksys_fadvise64_64 mm/fadvise.c:200 [inline]
 __do_sys_fadvise64 mm/fadvise.c:215 [inline]
 __se_sys_fadvise64 mm/fadvise.c:213 [inline]
 __x64_sys_fadvise64+0xc5/0x100 mm/fadvise.c:213
 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: 0x0000000000000003 -> 0x0000000000000005

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10130 Comm: syz-executor.1 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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