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Mon, 17 Aug 2026 18:44:50 -0700 (PDT) Received: from 192.168.1.6 ([140.213.202.182]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-14153073befsm9804468c88.7.2026.08.17.18.44.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 18:44:50 -0700 (PDT) From: Foxie Flakey X-Google-Original-From: Foxie Flakey Date: Tue, 18 Aug 2026 08:44:46 +0700 (WIB) To: Andrew Morton , Mike Rapoport , Peter Xu , Suren Baghdasaryan cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] userfaultfd: reset err to be 0 when move_pages_ptes succeeded Message-ID: <79cbfe54-41f2-9041-89f3-a96e9fb80066@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII >From 2599b924548175bef41ca6a601de58236a55a998 Mon Sep 17 00:00:00 2001 From: Foxie Flakey Date: Sun, 16 Aug 2026 23:03:46 +0700 Subject: [PATCH] userfaultfd: reset err to be 0 when move_pages_ptes succeeded 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. Fixes: 50944692052b ("userfaultfd: opportunistic TLB-flush batching for present pages in MOVE") Assisted-by: ChatGPT:GPT-5.6-Luna Signed-off-by: Foxie Flakey --- Changes in v2: - Updated on description to be easier to understood - Reset err before retrying, instead of fixing right at the move_pages_ptes branch. - Added Assisted-by, received an answer few days ago from linux-newbies IRC that even I just used AI/LLM as "fast path" of git bisect. I still need to add it following https://docs.kernel.org/process/coding-assistants.html doc. --- mm/userfaultfd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index c3adedaaf7d5..ec5d511bd179 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2085,8 +2085,10 @@ static ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, } if (err) { - if (err == -EAGAIN) + if (err == -EAGAIN) { + err = 0; continue; + } break; } base-commit: 62cc90241548d5570ee68e01aaba6506964e9811 -- 2.55.0