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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Masami Hiramatsu , Steven Rostedt , , Mathieu Desnoyers , Zach O'Keefe , , , Stephen Rothwell Subject: Re: [PATCH V5 0/2] mm/khugepaged: fix dirty page handling for MADV_COLLAPSE Message-Id: <20260118122229.dcdda884bbb19a9c30ec6f1e@linux-foundation.org> In-Reply-To: <20260118190939.8986-2-shivankg@amd.com> References: <20260118190939.8986-2-shivankg@amd.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D05ED40003 X-Stat-Signature: njtb9nygdko3r6ddcpo4s15sh56js1y4 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768767751-564243 X-HE-Meta: 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 cUUb7GS6 fWyWnzqMUYrnMu+A05Edmn6pxwgtI6/PLrdZXMC6sJyBMscVHqQJDt6Qwu2FihvsWC/20oaRK+tip6lRxvdI0V3FPMCthFGqsNkGZ3qYhwv44MXH00/JVzprFljv01ZSHzgnobjvv6N2C3TqMj7L3TqCLQda2xe/uU6FXrO79wjNtPIHpb4i7q9TssTEw+VhNYaW+sw10P8BfJP3Hsy7TrYKy/xhAu49hHRBXRp9L2MQemilZULik+hKXiD8U9FwZsCcx9XiWwmpOnxPrSdHsWIqAl4rxWbU6zlaSmswkQgXvwuEwPkDh8kOysB1x4A6IW9C8C/yRuFCR7ZTkHhSPXP+Dmg== 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 Sun, 18 Jan 2026 19:09:38 +0000 Shivank Garg wrote: > MADV_COLLAPSE on file-backed mappings fails with -EINVAL when TEXT pages > are dirty. This affects scenarios like package/container updates or > executing binaries immediately after writing them, etc. > > The issue is that collapse_file() triggers async writeback and returns > SCAN_FAIL (maps to -EINVAL), expecting khugepaged to revisit later. But > MADV_COLLAPSE is synchronous and userspace expects immediate success or > a clear retry signal. > > Reproduction: > - Compile or copy 2MB-aligned executable to XFS/ext4 FS > - Call MADV_COLLAPSE on .text section > - First call fails with -EINVAL (text pages dirty from copy) > - Second call succeeds (async writeback completed) > > Issue Report: > https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@amd.com Updated, thanks. Please tolerate a little whining about the timeliess here. We're at -rc6, v4 was added to mm.git over a month ago, had quite a lot of review, this is very close to being moved into the mm-stable branch and now we get v5. Argh. > V5: > - In patch 2/2, Simplify dirty writeback retry logic (David) Are you sure this is the only change? It looks like a lot for a simplification and I'm wondering if we should retain the v4 series and defer a simplification for separate consideration during the next cycle. Below is how this updated altered mm.git. Could reviewers please check this fairly soon? --- a/mm/khugepaged.c~b +++ a/mm/khugepaged.c @@ -2788,11 +2788,11 @@ int madvise_collapse(struct vm_area_stru hend = end & HPAGE_PMD_MASK; for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { - bool retried = false; int result = SCAN_FAIL; + bool triggered_wb = false; - if (!mmap_locked) { retry: + if (!mmap_locked) { cond_resched(); mmap_read_lock(mm); mmap_locked = true; @@ -2812,52 +2812,27 @@ retry: mmap_read_unlock(mm); mmap_locked = false; + *lock_dropped = true; result = hpage_collapse_scan_file(mm, addr, file, pgoff, cc); - fput(file); - } else { - result = hpage_collapse_scan_pmd(mm, vma, addr, - &mmap_locked, cc); - } - 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); + if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb && + mapping_can_writeback(file->f_mapping)) { 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); + triggered_wb = true; fput(file); - retried = true; goto retry; } + fput(file); + } else { + result = hpage_collapse_scan_pmd(mm, vma, addr, + &mmap_locked, cc); } + if (!mmap_locked) + *lock_dropped = true; handle_result: switch (result) { _