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BUG: KCSAN: data-race in ext4_ind_map_blocks / ext4_mark_iloc_dirty

write to 0xffff88811e99e28c of 4 bytes by task 21444 on cpu 1:
 ext4_splice_branch fs/ext4/indirect.c:447 [inline]
 ext4_ind_map_blocks+0x119f/0x1680 fs/ext4/indirect.c:636
 ext4_map_blocks+0x683/0xf60 fs/ext4/inode.c:628
 mpage_map_one_extent+0x10d/0x3c0 fs/ext4/inode.c:2377
 mpage_map_and_submit_extent fs/ext4/inode.c:2430 [inline]
 ext4_writepages+0xa4c/0x1ef0 fs/ext4/inode.c:2782
 do_writepages+0x7b/0x150 mm/page-writeback.c:2354
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:421
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:760
 ext4_sync_file+0xfc/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2882 [inline]
 ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:277
 ext4_file_write_iter+0x76f/0x1010 include/linux/fs.h:805
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x607/0x690 fs/read_write.c:578
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811e99e28c of 4 bytes by task 21456 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:5042 [inline]
 ext4_mark_iloc_dirty+0xce7/0x1660 fs/ext4/inode.c:5624
 __ext4_mark_inode_dirty+0x448/0x630 fs/ext4/inode.c:5818
 ext4_punch_hole+0x7f6/0xa20 fs/ext4/inode.c:4081
 ext4_fallocate+0xe5/0x560 fs/ext4/extents.c:4659
 vfs_fallocate+0x431/0x580 fs/open.c:309
 file_ioctl fs/ioctl.c:494 [inline]
 do_vfs_ioctl+0xde0/0xec0 fs/ioctl.c:732
 ksys_ioctl fs/ioctl.c:751 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0x81/0x130 fs/ioctl.c:760
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21456 Comm: syz-executor.2 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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