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BUG: KCSAN: data-race in ext4_mpage_readpages / ext4_setattr

write to 0xffff888109fc7238 of 8 bytes by task 24732 on cpu 0:
 i_size_write include/linux/fs.h:896 [inline]
 ext4_setattr+0xd61/0xec0 fs/ext4/inode.c:5386
 notify_change+0x7d4/0xa20 fs/attr.c:336
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x39f/0x3e0 fs/open.c:195
 __do_sys_ftruncate fs/open.c:205 [inline]
 __se_sys_ftruncate fs/open.c:203 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:203
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888109fc7238 of 8 bytes by task 24765 on cpu 1:
 ext4_readpage_limit fs/ext4/readpage.c:219 [inline]
 ext4_mpage_readpages+0x507/0x1380 fs/ext4/readpage.c:263
 ext4_readahead+0x93/0xa0 fs/ext4/inode.c:3242
 read_pages+0xa0/0x6b0 mm/readahead.c:130
 page_cache_readahead_unbounded+0x3ef/0x440 mm/readahead.c:244
 ondemand_readahead+0x4e4/0x6e0 mm/readahead.c:273
 page_cache_sync_readahead+0x178/0x1a0 mm/readahead.c:585
 generic_file_buffered_read+0x2ae/0x1800 mm/filemap.c:2033
 generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2307
 ext4_file_read_iter+0x2d6/0x420 fs/ext4/file.c:74
 call_read_iter include/linux/fs.h:1901 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:312
 do_splice_to fs/splice.c:870 [inline]
 splice_direct_to_actor+0x2a8/0x660 fs/splice.c:950
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x562/0xb10 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1576 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1568
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24765 Comm: syz-executor.1 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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