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BUG: KCSAN: data-race in ext4_alloc_da_blocks / ext4_da_reserve_space

write to 0xffff888135f9cdc8 of 4 bytes by task 11135 on cpu 0:
 ext4_da_reserve_space+0x147/0x200 fs/ext4/inode.c:1494
 ext4_insert_delayed_block fs/ext4/inode.c:1660 [inline]
 ext4_da_map_blocks fs/ext4/inode.c:1774 [inline]
 ext4_da_get_block_prep+0x512/0x9b0 fs/ext4/inode.c:1838
 __block_write_begin_int+0x4a2/0x1060 fs/buffer.c:2006
 __block_write_begin+0x2b/0x40 fs/buffer.c:2056
 ext4_da_write_begin+0x4a8/0x7f0 fs/ext4/inode.c:3024
 generic_perform_write+0x1a6/0x3d0 mm/filemap.c:3770
 ext4_buffered_write_iter+0x305/0x400 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x11a0
 call_write_iter include/linux/fs.h:2163 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x77d/0x8c0 fs/read_write.c:594
 ksys_write+0xce/0x180 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:656
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888135f9cdc8 of 4 bytes by task 11149 on cpu 1:
 ext4_alloc_da_blocks+0x1a/0xd0 fs/ext4/inode.c:3136
 __ext4_ioctl fs/ext4/ioctl.c:1041 [inline]
 ext4_ioctl+0xb8c/0x2110 fs/ext4/ioctl.c:1279
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:860
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000017 -> 0x0000001a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 11149 Comm: syz-executor.1 Tainted: G        W         5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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