+ userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded.patch added to mm-hotfixes-unstable branch

+ userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: userfaultfd: reset err to be 0 when move_pages_ptes succeeded
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Bryan Lim <foxieflakey@gmail.com>
Subject: userfaultfd: reset err to be 0 when move_pages_ptes succeeded
Date: Wed, 19 Aug 2026 10:08:24 +0700 (WIB)

During move_pages() operation, when move_pages_ptes() returns EAGAIN, the
error code is not cleared even after we processed it.  This leads to a
successful retry but then the same pages are retried again due to the
stale error code.  This time move fails because pages are already moved,
loop is terminated and move_pages() reports a failure.  Clear the error
code once we processes EAGAIN.

Link: https://lore.kernel.org/e1e0b5f8-c3c6-0537-670b-4397f822f980@gmail.com
Fixes: 50944692052b ("userfaultfd: opportunistic TLB-flush batching for present pages in MOVE")
Assisted-by: ChatGPT:GPT-5.6-Luna
Signed-off-by: Bryan Lim <foxieflakey@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/userfaultfd.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/userfaultfd.c~userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded
+++ a/mm/userfaultfd.c
@@ -2085,8 +2085,10 @@ static ssize_t move_pages(struct userfau
 		}
 
 		if (err) {
-			if (err == -EAGAIN)
+			if (err == -EAGAIN) {
+				err = 0;
 				continue;
+			}
 			break;
 		}
 
_

Patches currently in -mm which might be from foxieflakey@gmail.com are

userfaultfd-reset-err-to-be-0-when-move_pages_ptes-succeeded.patch