SUNRPC: don't pause on incomplete allocation

mainline inclusion
from mainline-v5.15-rc1
commit e38b3f20
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7RRY4
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e38b3f20059426a0adbde014ff71071739ab5226



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alloc_pages_bulk_array() attempts to allocate at least one page based on
the provided pages, and then opportunistically allocates more if that
can be done without dropping the spinlock.

So if it returns fewer than requested, that could just mean that it
needed to drop the lock.  In that case, try again immediately.

Only pause for a time if no progress could be made.

Reported-and-tested-by: Mike Javorski <mike.javorski@gmail.com>
Reported-and-tested-by: Lothar Paltins <lopa@mailbox.org>
Fixes: f6e70aab ("SUNRPC: refresh rq_pages using a bulk page allocator")
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Mel Gorman <mgorman@suse.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>

Conflicts:
    net/sunrpc/svc_xprt.c