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Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, richard.weiyang@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH mm-new 2/2] mm/khugepaged: merge PTE scanning logic into a new helper Date: Fri, 03 Oct 2025 13:11:23 -0400 X-Mailer: MailMate (2.0r6283) Message-ID: <9DF437D8-E98B-4061-A8C7-521D89070C97@nvidia.com> In-Reply-To: <20251002073255.14867-3-lance.yang@linux.dev> References: <20251002073255.14867-1-lance.yang@linux.dev> <20251002073255.14867-3-lance.yang@linux.dev> Content-Type: text/plain X-ClientProxiedBy: MN2PR18CA0016.namprd18.prod.outlook.com (2603:10b6:208:23c::21) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|IA1PR12MB8517:EE_ X-MS-Office365-Filtering-Correlation-Id: 921d2add-c70d-4099-6137-08de029fe2ca X-MS-Exchange-SenderADCheck: 1 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U2FsdGVkX1/5zZ7VVkRJhGOLetiBxdzHe/9ARm5/4usRSfqRCTkkbbutnq+H+l7q7ve5Yrz6SHNF+xXDz2DwZWWp8lTMzt9aracDDGKJKMyP+Fis193BMeqJ9nhCWOBBjOrzoGzrLH2HzYFxuLRdnjFN2D/E7PoA1PfB7KG1r6RzsJ3dG+duXwqJvnyBZUlNGLCWUWBYODhlKTnXXObhOm3Fw8CCgT9b8fejwdbr0ZjuWewWwvza72k1cs+C7tM7lEjTf35NPxjrMoDFm/3IppysdFBPRRWOJXEBNiRFWrBrDDyCzxEGij7fXORID0Et77ggVk/cMO2h3HHTQ7egEhXKWTHf4dXTQ1LMwXjcE1ywxC7XK7cZEp/K0Avnv+aVW6XDtsIAC2FKk3UQLKMLTeampklUrksCrSk1j7T1/6r35jqdy45ay5e1nxswmA+rKxfI/19CLZZ0sbLQR5Z+7zAldhLuu/UC/XlRBfro7+XKYEmzy0z8C5qorgbcUNzy9U6TWnaPWyQztUzS7O/cDm2KsYK1cLpAozZP2l2YdqNtF8U4rHBNT9BIOwmOJYtWilXe2/xwhYoZoU0PmtwaEqQgTgAJG4tucRk5X9ZR/k0tFiF2/6xwCC9aq2HtzaKQZSf3DV1nOdRXUdRti3MD7d69DbW3J0tU3YumzCCA+V/3P52BYa5L3PN2PgUI5ZUG8gtDxYhv/HIvn0iVAcQh2eXCaWe0Rd0Rh0DOvWFPFps67JuUeWAUufHFpmWvZ+WNB8eJFcQ1dr8Fc0L+l36Cg4o4leb4EzWiqr4A+dvgIRX9dprt+7og8LjKgv7Hg9itonfnGiHw4VDUnREM9jjBelMpatzZumBf7iPam2it50mcBGr0eSjOZc+9bH/re6j3xGoySZB0w67MgM2W8yG8FjcVTAsl8/v3tqMHN9Hwtqfi8OGSMD39xc7cB2AgdUCNjOn47FohhUMWU5QrksO 2m6WkZah Z+Ay7jrvNzY7sLEn/QhdfYWZX2fVru4CiRHP69Dk3UfJmaaaay1QdoTCNbkF07tSX9RvrhWpYMrIHjbJyDq65X8LTktIF4eDAiBAOt+kwWyTd+hXle/enXpbttWw5rx82UmcGWuaUAZ8r24awJxEO9LmjEad5xLQbXIR6BkxusYxnPINRQWnjlJzrcv4b0YQE7klUL2f26aCBrpfmPnNrCTIKU3n4+DP+sN0gGx/RGDqnFaS5y5jIk1m0IPzkhJFJDMq/ZZ8j4dtMDtLGS3P1nxscTpnK0ChS+pTEF2WT0tsX5yvh2IdVHaLgCaI5Sf8GsE4tz7mGOd62SQrllxO87MmQ4EyNUvUnbdf8TjmYGOgFNNtJjpc9gv6L/kcM2zjcLkAfMXL7dMiKkL93ZKn1+mKInreuPVENYnaD3qc9hRtfbKDuWhG7RrA6g6WOTH9r7/dipgTpNJ+A/w4= 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 2 Oct 2025, at 3:32, Lance Yang wrote: > From: Lance Yang > > As David suggested, the PTE scanning logic in hpage_collapse_scan_pmd() > and __collapse_huge_page_isolate() was almost duplicated. > > This patch cleans things up by moving all the common PTE checking logic > into a new shared helper, thp_collapse_check_pte(). > > Suggested-by: David Hildenbrand > Signed-off-by: Lance Yang > --- > mm/khugepaged.c | 167 ++++++++++++++++++++++++++++++------------------ > 1 file changed, 104 insertions(+), 63 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 808523f92c7b..2a897cfb1d03 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -61,6 +61,12 @@ enum scan_result { > SCAN_PAGE_FILLED, > }; > > +enum pte_check_result { > + PTE_CHECK_SUCCEED, > + PTE_CHECK_CONTINUE, > + PTE_CHECK_FAIL, > +}; > + > #define CREATE_TRACE_POINTS > #include > > @@ -533,6 +539,87 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, > } > } > > +/* > + * thp_collapse_check_pte - Check if a PTE is suitable for THP collapse > + * @pte: PTE to check > + * @vma: VMA the PTE belongs to > + * @cc: Collapse control settings > + * @scan_swap_pte: Allow scanning of swap PTEs if true > + * @none_or_zero: Counter for none/zero PTEs (must be non-NULL) > + * @unmapped: Counter for swap PTEs (must be non-NULL if scan_swap_pte > + * is true) > + * @scan_result: Used to return the failure reason (SCAN_*) on a > + * PTE_CHECK_FAIL return. Must be non-NULL > + * > + * Returns: > + * PTE_CHECK_SUCCEED - Valid PTE, proceed with collapse > + * PTE_CHECK_CONTINUE - Skip this none/zero PTE but continue scanning > + * PTE_CHECK_FAIL - Abort collapse scan > + */ > +static inline int thp_collapse_check_pte(pte_t pte, struct vm_area_struct *vma, > + struct collapse_control *cc, bool scan_swap_pte, > + int *none_or_zero, int *unmapped, int *scan_result) > +{ > + VM_BUG_ON(!none_or_zero || !scan_result); > + VM_BUG_ON(scan_swap_pte && !unmapped); Please use VM_WARN_ONCE_ON and just return. Or put all stats in a struct, pass and check the struct pointer instead. Best Regards, Yan, Zi