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Fri, 5 Sep 2025 05:13:17 -0400 (EDT) Date: Fri, 5 Sep 2025 10:13:15 +0100 From: Kiryl Shutsemau To: Pankaj Raghav Cc: Zi Yan , Ryan Roberts , David Hildenbrand , Lorenzo Stoakes , Baolin Wang , Barry Song , Andrew Morton , Nico Pache , Dev Jain , "Liam R . Howlett" , linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org, mcgrof@kernel.org, gost.dev@samsung.com, Pankaj Raghav Subject: Re: [PATCH v2] huge_memory: return -EINVAL in folio split functions when THP is disabled Message-ID: References: <20250904095129.222316-1-kernel@pankajraghav.com> <2psecfvsd4lbgcm6aflifi2kc6gof345txsvk7wtsytre5ehqt@4wyru36aaeel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 1hesrjz6cxnw9y4rzz6b7w3wdt51iwht X-Rspam-User: X-Rspamd-Queue-Id: BF517160007 X-Rspamd-Server: rspam05 X-HE-Tag: 1757063600-817079 X-HE-Meta: U2FsdGVkX185FKYAVwraTBR9rITpAP2amh+IsYuaD/Myz9iYlmp0/bHXLbAiwkRrLxROLzzN95caxEIkmG1K/Pz/eMy/64QXovvHGn+dkCEuA70sX//+N2FII1TFEevCWRV8reYD+M1Yog1hhmG4ON3w7Pk7mm/Go39zaJnZxmIq/9NXA5QVX2JHVEKnxhiuvp0EnzQdI8psZTpotZysY1OIB7OqszHNwNbibzjRtaogpAUzthK6OfZWrDKU8NOseXTPCcHgpDg0OV3XD7eNgguwl71iC7weNdxGibAWMHiY5IZJclUzmGwK8C9A6oZshd7rmiUqXqzAoywfBsvPNqb9Kj9ykWXD1HXR0m1djA74pM2bRg88SwfPp4Q5HfVguSCshZ2D2J6Hn+mhdzJXsBVCcj/BKJYmyF0IEvZnss5jnCVinGZiDm9espVqOJPa1bvcG89bP/TeyHP9hY63T0qxRX4yHExqao7d17puwHUQ6zq5WSyWXEk1JCKbnjogbKP6dhpW3K0+ixw3afjmcfffz2QoiDsFdVMgT5rnlBw0jQ9mtU6ihbfhnrJErJqYZRwtE69SutXlmiaAxQecRMP/cNRcQUPQRqQz/CaidsHH4UWv0s6wP4Rt5aLKt/3ZpGR8THDAeySzjzjQXW9gN3rLPdYkue1qW0y6MjavA09x55ev1+0GMqUNTqxLsTzavKBLvIvzrxuK+iMtzfUp2rQQhUC5YneEu8/JZDEAnNujmGS9CPCL8NP+Hs8jrzpPasvCXDh0W1EVMlvGYcY8QWTDy9xjajH9rVSVEccXVMfrit3mIBGuY0/BeE27vlc3y570tNDur7bUouMm1ArLM/n0/WVLQo7Dd6q2sKreL8pLs0HNEBU08Mby7/6RNWgujKDxhtova4Uqabzt3lqWHY6Freh8kU6mhZ6DPYvtFAP1RwPEXhbj31We6QZtb+Yg6gkafM2Owmuld/r05C6 fMevlIu+ O69HU831fVgjBA1k9levWmNy38kwhQ4CzOWpFlNykBLdHqZ72AWH4hLtce2jO7E5T9Q4asDCDLe0xE4Z2fZJLXCtH7zV0URAysOzjZ7LmDKXlFvpJsKIr7IyNoY9D+sS4Pdkd90uIlenNIswh5U0QwdtJ7aUBRNQPMOCDfNBMKEYrDX9Zra47Fyja+Jdi0M1SnMBm2Ax0yV9Ccpq6pzt4RqavoVPGscZNhtWIBflHOJrBWfLq+MkARe+pDs29HJQLcs7k97BHVGmXm/3DqcVMjCIDKKSKi7pis8fJrDEdP9+Vj5XSxQ/gtLVuT1UnPjuqkXtbTxjiQ4im3TJiRkpLk+DQ+VwRrmpsIo6lr+Wb3CO844LUUfUp9kwOSerMjdD/n5QaoGZ88yiGbiOGHyZ7MVOA8zWCpyIJ7pRU7pTKaCsP5gjDECFTbSTYemA30j/qBC/BRGG5rQ6BRhE= 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 Fri, Sep 05, 2025 at 10:13:05AM +0200, Pankaj Raghav wrote: > On 9/4/25 17:26, Kiryl Shutsemau wrote: > > On Thu, Sep 04, 2025 at 11:51:29AM +0200, Pankaj Raghav (Samsung) wrote: > >> From: Pankaj Raghav > >> > >> split_huge_page_to_list_[to_order](), split_huge_page() and > >> try_folio_split() return 0 on success and error codes on failure. > >> > >> When THP is disabled, these functions return 0 indicating success even > >> though an error code should be returned as it is not possible to split a > >> folio when THP is disabled. > >> > >> Make all these functions return -EINVAL to indicate failure instead of > >> 0. As large folios depend on CONFIG_THP, issue warning as this function > >> should not be called without a large folio. > >> > >> Signed-off-by: Pankaj Raghav > > > > Acked-by: Kiryl Shutsemau > > > > Just curious, did you give BUILD_BUG() a try? > > > > Yes, I tried BUILD_BUG() but it actually fails the build because truncate_inode_partial_folio() > calls try_folio_split(). > > It won't be called in runtime because there is a check for large folios before we call this > function. So a runtime warning is better in this case. If truncate_inode_partial_folio() shouldn't ever be calling on THP=n kernel, it also can be BUILD_BUG(). Just saying :P -- Kiryl Shutsemau / Kirill A. Shutemov