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Tue, 18 Aug 2026 20:08:28 -0700 (PDT) Received: from 192.168.1.6 ([140.213.202.182]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-327c2a92406sm127304eec.11.2026.08.18.20.08.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2026 20:08:27 -0700 (PDT) From: Foxie Flakey X-Google-Original-From: Foxie Flakey Date: Wed, 19 Aug 2026 10:08:24 +0700 (WIB) To: Andrew Morton , Mike Rapoport , Peter Xu , Suren Baghdasaryan cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] userfaultfd: reset err to be 0 when move_pages_ptes succeeded Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Queue-Id: 4D7DE80002 X-Rspamd-Server: rspam07 X-Stat-Signature: 9g5nj3kiahjunks8rhrddpdqes4izxs5 X-HE-Tag: 1787108909-633400 X-HE-Meta: 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 LXjDrkRG 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: Bryan Lim --- Changes in v3: - Updated to use proper sign off. 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; } -- 2.55.0