mm/page_alloc: correct return value of populated elements if bulk array is populated

mainline inclusion
from mainline-5.14-rc1
commit ff4b2b40
category: bugfix
bugzilla: https://gitee.com/src-openeuler/nfs-utils/issues/I46NSS
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff4b2b4014cbffb3d32b22629252f4dc8616b0fe

-------------------------------------------------

Dave Jones reported the following

	This made it into 5.13 final, and completely breaks NFSD for me
	(Serving tcp v3 mounts).  Existing mounts on clients hang, as do
	new mounts from new clients.  Rebooting the server back to rc7
	everything recovers.

The commit b3b64ebd ("mm/page_alloc: do bulk array bounds check after
checking populated elements") returns the wrong value if the array is
already populated which is interpreted as an allocation failure.  Dave
reported this fixes his problem and it also passed a test running dbench
over NFS.

Link: https://lkml.kernel.org/r/20210628150219.GC3840@techsingularity.net
Fixes: b3b64ebd ("mm/page_alloc: do bulk array bounds check after checking populated elements")
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Reported-by: NDave Jones <davej@codemonkey.org.uk>
Tested-by: NDave Jones <davej@codemonkey.org.uk>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org> [5.13+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit ff4b2b40)
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>
Reviewed-by: Ntong tiangen <tongtiangen@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/page_alloc.c

@@ -4965,7 +4965,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 
 	/* Already populated array? */
 	if (unlikely(page_array && nr_pages - nr_populated == 0))
-		return 0;
+		return nr_populated;
 
 	/* Use the single page allocator for one page. */
 	if (nr_pages - nr_populated == 1)