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Fri, 11 Sep 2026 15:47:47 +0000 X-Mizu-Trace-ID: bbdea84a56ccda99 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: baolin.wang@linux.alibaba.com Cc: akpm@linux-foundation.org, hughd@google.com, david@kernel.org, ziy@nvidia.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: shmem: ignore sysfs configs for shmem forced collapse Date: Fri, 11 Sep 2026 23:47:32 +0800 Message-Id: <20260911154732.31220-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 8BA03A0011 X-Stat-Signature: diy31584wd1z4fzago3f5cerz7b1b9px X-HE-Tag: 1789141669-934903 X-HE-Meta: U2FsdGVkX19cFigqW3T4EQteXQOz0+Axt2v8II+oRw2/BH/0t2HctmScuN666S4Gjyir0sTUgB4jvuBLDhbI7OFZLfmz/YBOGK9J/UdDkEibZEXk9OK6DzgKwKRqL/CxyYrEmArhfl81WHHpXtvyQKKLayieIdYqe+kJO1Oqfsc6mqONULFJLmt7y4t+U4sanOoeeqtHQ2k4Q3t3TSuAI2Kg84Ze+ajErK+RyPR2JkGIslSpQalusOOjSY8NNR2zb4GblPifAboGJr+t4ogtFhOAAr3TZkoE5Kz5+vdabTxTZf1pwjbLYWG6Qq/q+XtASqUIjdFd78cdfVfwFSfqmv+PUDh7qMugovId+zKGvw50ILMTlZ/NdsLjBgnkyAr5nfF67salBCRnQVD3ek6NTK60NmSNU0Secz7kUmLFvgTPh5HGsoMYX//+/WctVjN10Is0EdSuomdig4f32mcgKycSGHgJIGRvcblbb1IrlSEEt5GCMkQ80Oq/VuLAmaJMgFeiEvx3wvrDy2cWZmMYez5QuCgcEhcfOjC5fXl95oAqijb+bd5CuZLWO5z1DE6mJOpvIvOan4vTcGDFCVnF7uG+Z1bT+D2sT2vV5UxhNj0PgDUEiPiAWFF7ZH+QKHZfHwoEgQQxQUFWvXQahDNlSZ4Qa2elMFxN/5JvAV7DlAv5CBbe1/NvwnVOAWEuFIl8ttUAgdX5qYOWPis2LBDGTTHH0+3F1dDOzfv0FgFmQlkSUkJbPN9o2qLuk4MndO2jg8ZL9gU2jn8IfqfUdtIlce2nIf9nS2SCjnCE1r5Hm1Erqn3YXIWhs4CCVoprR0lz8PEIXDPrSjJpa9gl08f00sDde1hkCRJ+J8wT0XqCQrLcv2U3RTT7IOSJ1ZYJK0072W3M3Q46LMGiYijSSsE2frYYuk1K5W1RokEY2nVNn6/iFh+MESs1zb53yARZZjo8yFK6GtUSif1c29ZyCy1 nMUY1tjK W8E6wtNROl3HMRORkGi8MY4l+U38QQMw9P0Dr0+S5nVkDk6LnyoP1OyvHaKrGRsgsjpJdrWivIwEesKxeqL/LwYJl2zE1tNRl10vs7ErftDzc6v/1ojHv3iLwaPdBvtzVZUVo54DxtI+0JtcgxWbxrZ6FeHHByM6mK8dzc/e16LsslSLSsuOgARGwjXrj6WO4+LnpNc+DC6gbmLukijkhHpo62zXuUS/TfGIvUpA0N8rG0lYc642MeG31xMd/RF3M+VSovakJ3kUtMSXeRqw+hkoUIgeKeIPdNAyi Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 11, 2026 at 12:04:33PM +0800, Baolin Wang wrote: >According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to >ignore any THP or mTHP interface settings. > >However, after commit 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled() >into shmem_allowable_huge_orders()"), performing MADV_COLLAPSE on shmem >will depend on /sys/.../hugepages-2048kB/shmem_enabled being set to "inherit" >(although that is the default), which can cause MADV_COLLAPSE to fail >unexpectedly. > >Fix this by returning the result of shmem_huge_global_enabled() directly >when MADV_COLLAPSE is requested, allowing PMD-order collapse while ignoring >shmem THP/mTHP settings. > >Fixes: 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled() into shmem_allowable_huge_orders()") >Reported-by: Kiryl Shutsemau (Meta) >Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/ >Signed-off-by: Baolin Wang >--- With the Fixes tag corrected as Kiryl suggested, LGTM! Reviewed-by: Lance Yang