FAILED: patch "[PATCH] s390/uv: Don't return 0 from make_hva_secure() if the" failed to apply to 6.15-stable tree

The patch below does not apply to the 6.15-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-6.15.y
git checkout FETCH_HEAD
git cherry-pick -x 3ec8a8330a1aa846dffbf1d64479213366c55b54
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025062033-retold-crinkly-e6e3@gregkh' --subject-prefix 'PATCH 6.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 3ec8a8330a1aa846dffbf1d64479213366c55b54 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <[email protected]>
Date: Fri, 16 May 2025 14:39:44 +0200
Subject: [PATCH] s390/uv: Don't return 0 from make_hva_secure() if the
operation was not successful

If s390_wiggle_split_folio() returns 0 because splitting a large folio succeeded, we will return 0 from make_hva_secure() even though a retry is required. Return -EAGAIN in that case.

Otherwise, we'll return 0 from gmap_make_secure(), and consequently from unpack_one(). In kvm_s390_pv_unpack(), we assume that unpacking succeeded and skip unpacking this page. Later on, we run into issues and fail booting the VM.

So far, this issue was only observed with follow-up patches where we split large pagecache XFS folios. Maybe it can also be triggered with shmem?

We'll cleanup s390_wiggle_split_folio() a bit next, to also return 0 if no split was required.

Message-ID: <[email protected]>

index 9a5d5be8acf4..2cc3b599c7fe 100644
@@ -393,8 +393,11 @@ int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header
 	folio_walk_end(&fw, vma);
 	mmap_read_unlock(mm);
 
-	if (rc == -E2BIG || rc == -EBUSY)
+	if (rc == -E2BIG || rc == -EBUSY) {
 		rc = s390_wiggle_split_folio(mm, folio, rc == -E2BIG);
+		if (!rc)
+			rc = -EAGAIN;
+	}
 	folio_put(folio);
 
 	return rc;