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Fri, 11 Sep 2026 07:37:31 -0400 (EDT) Date: Fri, 11 Sep 2026 12:37:30 +0100 From: Kiryl Shutsemau To: Baolin Wang 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, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: shmem: ignore sysfs configs for shmem forced collapse Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9877BC000F X-Stat-Signature: 33aerdmp5346hm516rnh6u5y5ztc9cjr X-HE-Tag: 1789126658-357548 X-HE-Meta: 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 3yFTVWjw SR5VEmRplirjsOK3fbNxb15sB3ODoCCuR85Mc3YNDodIssek99l+0Gr+FuxN5dovNs6IO+U0sFlJPK+ADca0ui5IW9kj+CRYy3pNT1+Eo8qxltPRmL13RTomuREGAACSLMn0zgVfhtNf50Iih9lGeyndbz2vcrimYOq60JlayMZMd4WfizJdS9+kE+1YGzeUxyC0MJ7+a3NaCAdElNclc0K6L9KPhez7mA+plad4ApFVlg7QSey+J8xVQWhkRCqxKACcvkQqRzwgy/MzpzWvMMabD+6kjmz5IWs/qWGmax9He5gklyQfi0PRKtkPGkCWhz/OKOsd4WhfNEqQ= 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()") Hm. I don't think it is the right Fixes tag. "No functional changes" in its commit message seems to be true. This might be a better fit: Fixes: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem") > Reported-by: Kiryl Shutsemau (Meta) > Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/ > Signed-off-by: Baolin Wang Thanks! Reviewed-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov