FAILED: patch "[PATCH] selftests/mm: ksm_tests should only MADV_HUGEPAGE valid" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x d021b442cf312664811783e92b3d5e4548e92a53
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024021805-nuzzle-apricot-89e9@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d021b442cf312664811783e92b3d5e4548e92a53 Mon Sep 17 00:00:00 2001
From: Ryan Roberts <[email protected]>
Date: Mon, 22 Jan 2024 12:05:54 +0000
Subject: [PATCH] selftests/mm: ksm_tests should only MADV_HUGEPAGE valid
memory

ksm_tests was previously mmapping a region of memory, aligning the returned pointer to a PMD boundary, then setting MADV_HUGEPAGE, but was setting it past the end of the mmapped area due to not taking the pointer alignment into consideration. Fix this behaviour.

Up until commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP boundaries"), this buggy behavior was (usually) masked because the alignment difference was always less than PMD-size. But since the mentioned commit, ksm_tests -H -s 100 started failing.

index 380b691d3eb9..b748c48908d9 100644
@@ -566,7 +566,7 @@ static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
 	if (map_ptr_orig == MAP_FAILED)
 		err(2, "initial mmap");
 
-	if (madvise(map_ptr, len + HPAGE_SIZE, MADV_HUGEPAGE))
+	if (madvise(map_ptr, len, MADV_HUGEPAGE))
 		err(2, "MADV_HUGEPAGE");
 
 	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);