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BUG: KCSAN: data-race in ext4_ext_insert_extent / ext4_mark_iloc_dirty

write to 0xffff8880bad9046a of 2 bytes by task 14116 on cpu 0:
 ext4_ext_store_pblock fs/ext4/ext4_extents.h:256 [inline]
 ext4_ext_insert_extent+0x124d/0x2b80 fs/ext4/extents.c:2121
 ext4_ext_map_blocks+0x1776/0x20c0 fs/ext4/extents.c:4265
 ext4_map_blocks+0x6d3/0xf60 fs/ext4/inode.c:626
 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
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:654
 filemap_write_and_wait include/linux/fs.h:2765 [inline]
 iomap_bmap+0x68/0x110 fs/iomap/fiemap.c:130
 ext4_bmap+0x20b/0x220 fs/ext4/inode.c:3215
 bmap+0x56/0x80 fs/inode.c:1703
 ioctl_fibmap fs/ioctl.c:74 [inline]
 file_ioctl fs/ioctl.c:531 [inline]
 do_vfs_ioctl+0xd44/0xec0 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:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bad90468 of 4 bytes by task 14113 on cpu 1:
 ext4_do_update_inode fs/ext4/inode.c:5042 [inline]
 ext4_mark_iloc_dirty+0xdcf/0x1660 fs/ext4/inode.c:5624
 __ext4_mark_inode_dirty+0x448/0x630 fs/ext4/inode.c:5818
 ext4_dirty_inode+0xa6/0xc0 fs/ext4/inode.c:5854
 __mark_inode_dirty+0x72/0x7e0 fs/fs-writeback.c:2258
 mark_inode_dirty include/linux/fs.h:2192 [inline]
 generic_write_end+0x166/0x220 fs/buffer.c:2203
 ext4_da_write_end+0x57e/0x760 fs/ext4/inode.c:3092
 generic_perform_write+0x23b/0x390 mm/filemap.c:3310
 ext4_buffered_write_iter+0x2cc/0x3b0 fs/ext4/file.c:270
 ext4_file_write_iter+0x76f/0x1010 include/linux/fs.h:804
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0x2d8/0x340 fs/read_write.c:497
 vfs_write+0x19b/0x350 fs/read_write.c:559
 ksys_write+0xce/0x180 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+0x3e/0x50 fs/read_write.c:621
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14113 Comm: syz-executor.4 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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