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BUG: KCSAN: data-race in __add_to_page_cache_locked / ext4_writepages

write to 0xffff888128e3f438 of 8 bytes by task 23653 on cpu 0:
 __add_to_page_cache_locked+0x28a/0x770 mm/filemap.c:868
 add_to_page_cache_lru+0xc7/0x260 mm/filemap.c:921
 ext4_mpage_readpages+0x310/0x1400 fs/ext4/readpage.c:259
 ext4_readpages+0x8e/0xb0 fs/ext4/inode.c:3245
 read_pages+0xa2/0x2d0 mm/readahead.c:126
 __do_page_cache_readahead+0x358/0x380 mm/readahead.c:212
 ra_submit mm/internal.h:62 [inline]
 ondemand_readahead+0x369/0x730 mm/readahead.c:492
 page_cache_async_readahead+0x237/0x260 mm/readahead.c:574
 generic_file_buffered_read mm/filemap.c:2037 [inline]
 generic_file_read_iter+0xff2/0x1490 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x103/0x360 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 new_sync_read+0x306/0x450 fs/read_write.c:414
 __vfs_read+0x9e/0xb0 fs/read_write.c:427
 integrity_kernel_read+0x97/0xe0 security/integrity/iint.c:200
 ima_calc_file_hash_tfm+0x18f/0x240 security/integrity/ima/ima_crypto.c:360
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:391 [inline]
 ima_calc_file_hash+0x147/0xeb0 security/integrity/ima/ima_crypto.c:456
 ima_collect_measurement+0x385/0x3b0 security/integrity/ima/ima_api.c:249
 process_measurement+0x91a/0x1000 security/integrity/ima/ima_main.c:326
 ima_file_check+0x7e/0xb0 security/integrity/ima/ima_main.c:442
 do_last fs/namei.c:3494 [inline]
 path_openat+0xdef/0x2f70 fs/namei.c:3607
 do_filp_open+0x11e/0x1b0 fs/namei.c:3637
 do_sys_openat2+0x4f5/0x620 fs/open.c:1149
 do_sys_open+0xa2/0x110 fs/open.c:1165
 ksys_open include/linux/syscalls.h:1386 [inline]
 __do_sys_open fs/open.c:1171 [inline]
 __se_sys_open fs/open.c:1169 [inline]
 __x64_sys_open+0x50/0x60 fs/open.c:1169
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888128e3f438 of 8 bytes by task 23549 on cpu 1:
 ext4_writepages+0x181/0x1d40 fs/ext4/inode.c:2639
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1bb/0x220 mm/filemap.c:421
 filemap_write_and_wait_range mm/filemap.c:654 [inline]
 filemap_write_and_wait_range+0xad/0x140 mm/filemap.c:648
 iomap_dio_rw+0x3a2/0x9a0 fs/iomap/direct-io.c:471
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter fs/ext4/file.c:129 [inline]
 ext4_file_read_iter+0x2b4/0x360 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x2df/0x470 fs/splice.c:313
 do_splice_to+0xc7/0x100 fs/splice.c:892
 splice_direct_to_actor+0x1b9/0x540 fs/splice.c:971
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23549 Comm: syz-executor.0 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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