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b=pw4B/tZv7K+RDI7ncSfjgc7Xoms5biqKDoIU6JHPsU017gpdwrF1fdqRBvNZ3xhaA 9D53P3RktGoUn1C64cj31m5I+GDEkbCHE5Y49Z6o6U1yellQZkMngVS+R/qhccSKBM 5aHyOgxcnaHBPcBncentvbCUzc8rxjSxGdo8RiC8= Date: Wed, 12 Aug 2026 15:58:29 -0700 From: Andrew Morton To: liuqiangneo@163.com Cc: jgg@ziepe.ca, leon@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qiang Liu Subject: Re: [PATCH v2] lib/test_hmm: fix garbage pfn and wrong direction in devmem fault debug Message-Id: <20260812155829.43ebf2838420b8dcab83f55d@linux-foundation.org> In-Reply-To: <20260812092856.55296-1-liuqiangneo@163.com> References: <20260812092856.55296-1-liuqiangneo@163.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 559C3A0003 X-Rspamd-Server: rspam07 X-Stat-Signature: 3am87fcq5tp1g9h1dgaxzsxnyxtzxz4h X-HE-Tag: 1786575512-575389 X-HE-Meta: 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 YCbl+qMq 4h7bICEg4NHJixhSmHDeUkXxTQbB+EjO2NAUshIsyDP3EoN8MesN8uae5Wkaah2f+LCxq1XeGsifhKcgju1uVOJHRtvduvpukEUOwMn3nW7heKm8G8ojRMkHw/SkDA4c1kWGpeIVXK2eS5x796zpV5Cv25zEomKKzpbsIXbI3HupcpNSfdHLEXLb6Gt3kX3Aq387ARrxsXsFFh3G/Ue643YKS/ChK+Xwl+o0T2ZJ924NWAtItQeKiUgOZbKZipEboKGxWmDAeb1ZGvTtxy8QJ+qPWzaoa1dkAFUoxK0cwxESIw7mb/GrQjzUqm6kVlI+jbOt0pTkVO64P4H2odK70YXEcr1hbGwgRMOw3K/0DeR8fKKKsNiRXlGaRJXNxH2maeo9e Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 12 Aug 2026 17:28:56 +0800 liuqiangneo@163.com wrote: > From: Qiang Liu > > Move pr_debug() inside the `if (dpage)` block to avoid > printing garbage pfn for NULL dpage, and correct the > direction label from "sys to dev" to "dev to sys". > > ... > > --- a/lib/test_hmm.c > +++ b/lib/test_hmm.c > @@ -1151,10 +1151,9 @@ static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args, > if (!dpage && !order) > return VM_FAULT_OOM; > > - pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n", > - page_to_pfn(spage), page_to_pfn(dpage)); > - > if (dpage) { > + pr_debug("migrating from dev to sys pfn src: 0x%lx pfn dst: 0x%lx\n", > + page_to_pfn(spage), page_to_pfn(dpage)); > lock_page(dpage); > *dst |= migrate_pfn(page_to_pfn(dpage)); Looks OK to me, thanks. We could just remove the pr_debug. I suspect it was a development-time thing and nobody uses it any more. Your patch prompted Sashiko to find three possible pre-existing issues in this code: https://sashiko.dev/#/patchset/20260812092856.55296-1-liuqiangneo@163.com