==================================================================
BUG: KCSAN: data-race in ext4_ext_insert_extent / ext4_mark_iloc_dirty

write to 0xffff88812c07195c of 4 bytes by task 32550 on cpu 1:
 ext4_ext_store_pblock fs/ext4/ext4_extents.h:255 [inline]
 ext4_ext_insert_extent+0x1235/0x2bc0 fs/ext4/extents.c:2116
 ext4_ext_map_blocks+0x167d/0x1f00 fs/ext4/extents.c:4259
 ext4_map_blocks+0x70d/0xef0 fs/ext4/inode.c:638
 mpage_map_one_extent+0x10d/0x360 fs/ext4/inode.c:2397
 mpage_map_and_submit_extent fs/ext4/inode.c:2450 [inline]
 ext4_writepages+0xc1a/0x1d10 fs/ext4/inode.c:2802
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __writeback_single_inode+0x80/0x450 fs/fs-writeback.c:1467
 writeback_sb_inodes+0x564/0xf10 fs/fs-writeback.c:1732
 wb_writeback+0x28e/0x700 fs/fs-writeback.c:1905
 wb_do_writeback+0x101/0x510 fs/fs-writeback.c:2050
 wb_workfn+0xc8/0x520 fs/fs-writeback.c:2091
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 worker_thread+0x636/0xae0 kernel/workqueue.c:2421
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88812c07195c of 4 bytes by task 8 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:5111 [inline]
 ext4_mark_iloc_dirty+0xe02/0x1750 fs/ext4/inode.c:5726
 __ext4_mark_inode_dirty+0x4db/0x5b0 fs/ext4/inode.c:5920
 ext4_convert_unwritten_extents+0x1f9/0x2c0 fs/ext4/extents.c:4768
 ext4_convert_unwritten_io_end_vec+0xa4/0x130 fs/ext4/extents.c:4799
 ext4_end_io_end fs/ext4/page-io.c:184 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
 ext4_end_io_rsv_work+0x198/0x360 fs/ext4/page-io.c:271
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 worker_thread+0x636/0xae0 kernel/workqueue.c:2421
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
==================================================================
EXT4-fs: 318 callbacks suppressed
EXT4-fs (sda1): Delayed block allocation failed for inode 15945 at logical offset 0 with max blocks 1 with error 28
EXT4-fs (sda1): This should not happen!! Data will be lost

EXT4-fs (sda1): Total free blocks count 0
EXT4-fs (sda1): Free/Dirty block details
EXT4-fs (sda1): free_blocks=13639
EXT4-fs (sda1): dirty_blocks=8929
EXT4-fs (sda1): Block reservation details
EXT4-fs (sda1): i_reserved_data_blocks=1
EXT4-fs (sda1): Delayed block allocation failed for inode 13847 at logical offset 135 with max blocks 1 with error 28
EXT4-fs (sda1): This should not happen!! Data will be lost