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BUG: KCSAN: data-race in ext4_alloc_da_blocks / ext4_da_reserve_space

read to 0xffff8881251c5df0 of 4 bytes by task 9460 on cpu 1:
 ext4_alloc_da_blocks+0x4b/0x180 fs/ext4/inode.c:3111
 ext4_ioctl+0xf0d/0x3290 fs/ext4/ioctl.c:1045
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x84f/0xcf0 fs/ioctl.c:732
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:754
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881251c5df0 of 4 bytes by task 9454 on cpu 0:
 ext4_da_reserve_space+0x13f/0x280 fs/ext4/inode.c:1470
 ext4_insert_delayed_block fs/ext4/inode.c:1633 [inline]
 ext4_da_map_blocks fs/ext4/inode.c:1748 [inline]
 ext4_da_get_block_prep+0x87f/0xa60 fs/ext4/inode.c:1812
 ext4_block_write_begin+0x33e/0xba0 fs/ext4/inode.c:1055
 ext4_da_write_begin+0x208/0x840 fs/ext4/inode.c:2996
 generic_perform_write+0x136/0x320 mm/filemap.c:3309
 ext4_buffered_write_iter+0x143/0x290 fs/ext4/file.c:252
 ext4_file_write_iter+0xf4/0xd40 fs/ext4/file.c:547
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9454 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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