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BUG: KCSAN: data-race in ext4_write_end / mpage_submit_page

write to 0xffff888128e9ebb8 of 8 bytes by task 558 on cpu 0:
 i_size_write include/linux/fs.h:888 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:2982 [inline]
 ext4_write_end+0x304/0x800 fs/ext4/inode.c:1288
 ext4_da_write_end+0x2e4/0x620 fs/ext4/inode.c:3060
 generic_perform_write+0x1d3/0x320 mm/filemap.c:3320
 ext4_buffered_write_iter+0x143/0x290 fs/ext4/file.c:252
 ext4_file_write_iter+0xf4/0xd40 fs/ext4/file.c:547
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888128e9ebb8 of 8 bytes by task 351 on cpu 1:
 mpage_submit_page+0x81/0x1a0 fs/ext4/inode.c:2069
 mpage_map_and_submit_buffers+0x3c4/0x6c0 fs/ext4/inode.c:2319
 mpage_map_and_submit_extent fs/ext4/inode.c:2458 [inline]
 ext4_writepages+0x1449/0x2500 fs/ext4/inode.c:2771
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1452
 writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1716
 wb_writeback+0x1f9/0x6a0 fs/fs-writeback.c:1892
 wb_do_writeback fs/fs-writeback.c:2037 [inline]
 wb_workfn+0x22e/0x970 fs/fs-writeback.c:2078
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 351 Comm: kworker/u4:0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
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