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b=jd7uHjY0rT97aWkhW+uvWagPzLhpTIpnVX1P+4zXYSoEihJj3TO4Su2GB/OJtkGts I5aBvcoEgPpu/ylyHr+CAy8qEEcPbPClOMLu4kVj+1+66PFzaM5cLG++HybBUE5k9S V4NWqpLFpCqSyCrXpwBIS2oM/DBGGf30pxQosp8oVMDgbAAYvFmHctdnquJ5+mRMUy Jd5OSloYqUa5Q5PQBsw97UWA2WG7xOhEuoH+gKGWgbVrj0HtKkgvAIcT+FtrnzSBWT /F34102/l6pDKi8ZgrEI5Z4cVDSmOXXB5LBq7S03Z9bCesj6IrDVpcRaaJCju4jg95 6sfIT4CJrh+XA== Date: Mon, 2 Sep 2024 16:21:09 +0200 From: Christian Brauner To: Matthew Wilcox , "Pankaj Raghav (Samsung)" Cc: sfr@canb.auug.org.au, akpm@linux-foundation.org, linux-next@vger.kernel.org, mcgrof@kernel.org, ziy@nvidia.com, da.gomez@samsung.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Pankaj Raghav , Sven Schnelle Subject: Re: [PATCH] mm: don't convert the page to folio before splitting in split_huge_page() Message-ID: <20240902-wovor-knurren-01ba56e0460e@brauner> References: <20240902124931.506061-2-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 300A84001B X-Stat-Signature: rfam6ambt9gm9h8bi9zwf1h7swibmdo7 X-HE-Tag: 1725286876-280055 X-HE-Meta: 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 KxRPROGp zhHhtpElSuxfr7BddiofhFl18LWIA9fEad8fgyhh9wDsElL4kdRbiOo75Ax9dOEdiEhBSQxf5MO+N+/IIEsbIGoqN7ZaqazdJMjLNn7yahlHqMJ82VDvAal8rIE0isoqalRljOXIXB14AL+UgSvLEKpsm4Ha1EgpwiyImYbAFGWKCoK6UsM1hXjvG4h6WMEvmRckXG24XRGRtMSCeKuyhv4dm4uIBiE6eCzxK+IghiXbLYoVkr3vtF2afrP54UCzaz/DLYwz85aQSDKU0yeSqdFO0pFB8Ehq9zM3gXUxC25X4J0pYjeHGUKuZdUqk5SY/MtFCVDx2GmhGatS7um8iM+5N31htMTwp0dSP X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 02, 2024 at 03:00:37PM GMT, Matthew Wilcox wrote: > On Mon, Sep 02, 2024 at 02:49:32PM +0200, Pankaj Raghav (Samsung) wrote: > > From: Pankaj Raghav > > > > Sven reported that a commit from bs > ps series was breaking the ksm ltp > > test[1]. > > > > split_huge_page() takes precisely a page that is locked, and it also > > expects the folio that contains that page to be locked after that > > huge page has been split. The changes introduced converted the page to > > folio, and passed the head page to be split, which might not be locked, > > resulting in a kernel panic. > > > > This commit fixes it by always passing the correct page to be split from > > split_huge_page() with the appropriate minimum order for splitting. > > This should be folded into the patch that is broken, not be a separate > fix commit, otherwise it introduces a bisection hazard which are to be > avoided when possible. Patch folded into "mm: split a folio in minimum folio order chunks" with the Link to this patch. Please double-check.