raid10: cleanup memleak at raid10_make_request

In the Linux kernel, the following vulnerability has been resolved:

raid10: cleanup memleak at raid10_make_request

If raid10_read_request or raid10_write_request registers a new

request and the REQ_NOWAIT flag is set, the code does not

free the malloc from the mempool.

unreferenced object 0xffff8884802c3200 (size 192):

comm "fio", pid 9197, jiffies 4298078271

hex dump (first 32 bytes):

00 00 00 00 00 00 00 00 88 41 02 00 00 00 00 00 .........A......

08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

backtrace (crc c1a049a2):

__kmalloc+0x2bb/0x450

mempool_alloc+0x11b/0x320

raid10_make_request+0x19e/0x650 [raid10]

md_handle_request+0x3b3/0x9e0

__submit_bio+0x394/0x560

__submit_bio_noacct+0x145/0x530

submit_bio_noacct_nocheck+0x682/0x830

__blkdev_direct_IO_async+0x4dc/0x6b0

blkdev_read_iter+0x1e5/0x3b0

__io_read+0x230/0x1110

io_read+0x13/0x30

io_issue_sqe+0x134/0x1180

io_submit_sqes+0x48c/0xe90

__do_sys_io_uring_enter+0x574/0x8b0

do_syscall_64+0x5c/0xe0

entry_SYSCALL_64_after_hwframe+0x76/0x7e

V4: changing backing tree to see if CKI tests will pass.

The patch code has not changed between any versions.