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BUG: KCSAN: data-race in ext4_handle_inode_extension / ext4_set_iomap

write to 0xffff888036be4c38 of 8 bytes by task 28686 on cpu 1:
 i_size_write include/linux/fs.h:894 [inline]
 ext4_update_inode_size fs/ext4/ext4.h:3083 [inline]
 ext4_handle_inode_extension+0x3b4/0x580 fs/ext4/file.c:330
 ext4_dio_write_iter fs/ext4/file.c:536 [inline]
 ext4_file_write_iter+0x812/0xd30 fs/ext4/file.c:640
 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 0xffff888036be4c38 of 8 bytes by task 28701 on cpu 0:
 ext4_set_iomap+0x10a/0x470 fs/ext4/inode.c:3323
 ext4_iomap_begin_report+0x3de/0x410 fs/ext4/inode.c:3569
 iomap_apply+0xd4/0x660 fs/iomap/apply.c:46
 iomap_fiemap+0xd1/0x200 fs/iomap/fiemap.c:88
 _ext4_fiemap+0x36a/0x430 fs/ext4/extents.c:4860
 ext4_fiemap+0x36/0x50 fs/ext4/extents.c:4885
 ioctl_fiemap fs/ioctl.c:226 [inline]
 do_vfs_ioctl+0x5e1/0xd00 fs/ioctl.c:715
 ksys_ioctl+0xb2/0x150 fs/ioctl.c:761
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28701 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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