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BUG: KCSAN: data-race in ext4_write_end / mpage_submit_page

read to 0xffff8880b59f8628 of 8 bytes by task 8145 on cpu 1:
 mpage_submit_page+0x81/0x170 fs/ext4/inode.c:2216
 mpage_map_and_submit_buffers+0x331/0x520 fs/ext4/inode.c:2422
 mpage_map_and_submit_extent fs/ext4/inode.c:2556 [inline]
 ext4_writepages+0x1458/0x2300 fs/ext4/inode.c:2869
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaf/0x8e0 fs/fs-writeback.c:1449
 writeback_sb_inodes+0x4ba/0xa50 fs/fs-writeback.c:1713
 wb_writeback+0x1f9/0x6a0 fs/fs-writeback.c:1889
 wb_do_writeback fs/fs-writeback.c:2034 [inline]
 wb_workfn+0x22e/0x970 fs/fs-writeback.c:2075
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff8880b59f8628 of 8 bytes by task 26545 on cpu 0:
 i_size_write include/linux/fs.h:888 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:2979 [inline]
 ext4_write_end+0x5ae/0x760 fs/ext4/inode.c:1435
 ext4_da_write_end+0x2e4/0x620 fs/ext4/inode.c:3158
 generic_perform_write+0x1d3/0x320 mm/filemap.c:3316
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3434
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [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/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26545 Comm: syz-executor.4 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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