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Howlett" , Nico Pache , Andrew Morton , Ryan Roberts , Dev Jain , Lorenzo Stoakes , Barry Song , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Zach O'Keefe , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Branden Moore References: <20251201185604.210634-6-shivankg@amd.com> <20251201185604.210634-10-shivankg@amd.com> Content-Language: en-US From: "Garg, Shivank" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BM1P287CA0009.INDP287.PROD.OUTLOOK.COM (2603:1096:b00:40::17) To SJ0PR12MB7458.namprd12.prod.outlook.com (2603:10b6:a03:48d::13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ0PR12MB7458:EE_|SA1PR12MB8987:EE_ X-MS-Office365-Filtering-Correlation-Id: 06edb5b7-5482-454a-8a09-08de32996acb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016; 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If the collapse fails due to dirty pages, perform >> synchronous writeback on the specific range and retry once. >> >> This avoids spurious failures for freshly written executables while >> avoiding unnecessary synchronous I/O for mappings that are already clean. >> >> Reported-by: Branden Moore >> Closes: https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@amd.com >> Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE") >> Suggested-by: David Hildenbrand >> Signed-off-by: Shivank Garg >> --- >>   mm/khugepaged.c | 41 +++++++++++++++++++++++++++++++++++++++++ >>   1 file changed, 41 insertions(+) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 219dfa2e523c..7a12e9ef30b4 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -22,6 +22,7 @@ >>   #include >>   #include >>   #include >> +#include >>     #include >>   #include "internal.h" >> @@ -2787,9 +2788,11 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, >>       hend = end & HPAGE_PMD_MASK; >>         for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { >> +        bool retried = false; >>           int result = SCAN_FAIL; >>             if (!mmap_locked) { >> +retry: >>               cond_resched(); >>               mmap_read_lock(mm); >>               mmap_locked = true; >> @@ -2819,6 +2822,44 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, >>           if (!mmap_locked) >>               *lock_dropped = true; >>   +        /* >> +         * If the file-backed VMA has dirty pages, the scan triggers >> +         * async writeback and returns SCAN_PAGE_DIRTY_OR_WRITEBACK. >> +         * Since MADV_COLLAPSE is sync, we force sync writeback and >> +         * retry once. >> +         */ >> +        if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !retried) { >> +            /* >> +             * File scan drops the lock. We must re-acquire it to >> +             * safely inspect the VMA and hold the file reference. >> +             */ >> +            if (!mmap_locked) { >> +                cond_resched(); >> +                mmap_read_lock(mm); >> +                mmap_locked = true; >> +                result = hugepage_vma_revalidate(mm, addr, false, &vma, cc); >> +                if (result != SCAN_SUCCEED) >> +                    goto handle_result; >> +            } >> + >> +            if (!vma_is_anonymous(vma) && vma->vm_file && >> +                mapping_can_writeback(vma->vm_file->f_mapping)) { >> +                struct file *file = get_file(vma->vm_file); >> +                pgoff_t pgoff = linear_page_index(vma, addr); >> +                loff_t lstart = (loff_t)pgoff << PAGE_SHIFT; >> +                loff_t lend = lstart + HPAGE_PMD_SIZE - 1; >> + >> +                mmap_read_unlock(mm); >> +                mmap_locked = false; >> +                *lock_dropped = true; >> +                filemap_write_and_wait_range(file->f_mapping, lstart, lend); >> +                fput(file); >> +                retried = true; >> +                goto retry; >> +            } >> +        } >> + >> + > > Nit: spurious blank line. Ah, I completely missed this. I’ll fix it in the next version. Hope the rest of the patch looks reasonable. Thanks for the review. Thanks, Shivank > >>   handle_result: >>           switch (result) { >>           case SCAN_SUCCEED: >