syzbot

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BUG: KCSAN: data-race in ext4_write_end / mpage_submit_page

write to 0xffff888120fde9b8 of 8 bytes by task 11723 on cpu 0:
 i_size_write include/linux/fs.h:894 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:3083 [inline]
 ext4_write_end+0x30d/0x920 fs/ext4/inode.c:1286
 generic_perform_write+0x1d7/0x320 mm/filemap.c:3313
 ext4_buffered_write_iter+0x14e/0x280 fs/ext4/file.c:270
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write+0x303/0x400 fs/read_write.c:484
 __vfs_write+0x9e/0xb0 fs/read_write.c:497
 vfs_write fs/read_write.c:559 [inline]
 vfs_write+0x189/0x380 fs/read_write.c:543
 ksys_write+0xc5/0x1a0 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x49/0x60 fs/read_write.c:621
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888120fde9b8 of 8 bytes by task 29 on cpu 1:
 mpage_submit_page+0x78/0x190 fs/ext4/inode.c:2067
 mpage_process_page_bufs+0x3df/0x400 fs/ext4/inode.c:2187
 mpage_prepare_extent_to_map+0x43b/0x6e0 fs/ext4/inode.c:2595
 ext4_writepages+0x5a1/0x1e10 fs/ext4/inode.c:2723
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __writeback_single_inode+0xaa/0x910 fs/fs-writeback.c:1452
 writeback_sb_inodes+0x4c8/0xa10 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+0x215/0x970 fs/fs-writeback.c:2078
 process_one_work+0x424/0x930 kernel/workqueue.c:2268
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2414
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29 Comm: kworker/u4:2 Not tainted 5.7.0-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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