From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5902CD1A639 for ; Fri, 9 Jan 2026 14:46:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B062B6B0089; Fri, 9 Jan 2026 09:46:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AD0886B008A; Fri, 9 Jan 2026 09:46:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9DCE96B008C; Fri, 9 Jan 2026 09:46:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 8DA736B0089 for ; Fri, 9 Jan 2026 09:46:37 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 4CEBF1ACE2D for ; Fri, 9 Jan 2026 14:46:37 +0000 (UTC) X-FDA: 84312701634.09.868689B Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf01.hostedemail.com (Postfix) with ESMTP id 8B1C340013 for ; Fri, 9 Jan 2026 14:46:35 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uZUjYGj2; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767969995; a=rsa-sha256; cv=none; b=u/SHpRtA+9D9AOMjAnX2msteoPPy0/rr6ZnVDejAvUK+PSQAq3v6A4ribXDiWxjdpHl8sC MydSeSlTN9yGI/54nJKzvzU0pigTnMIW2gUc0k8/f6BgPyJT6sPrjf32KxZ2JPvddlBYo3 F54bzLtaMSvyo9idfWcW63oyRdfBnJE= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uZUjYGj2; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767969995; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=n1P/dCqO1tgBzOYNKJaI6BoPW82uloKdtpWKI9Dc1bY=; b=qBXlLTl+/QAN28U5x4Nt9Fci+5tx/FHH+VCR++b5XvCrri2fPyhJwtm/C28L3KWw6VHCIX dFz1wc2RHy/9Rjn2DawrwWVqqdq5ybFN9MF1U4anbX4M6McvWo51yY4PdFLo+gt/Xr/PIE 4DtoXlt0WpTS2AvrHdQDBxFMln4loZc= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id D769A60145; Fri, 9 Jan 2026 14:46:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE468C4CEF1; Fri, 9 Jan 2026 14:46:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767969994; bh=TiX3+Mf2/1XrF5Wi9iq9L5ZAotC8Ji5SdKgsf6S+mLw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=uZUjYGj2vzAU/895Kp1TsSc1LFPAvhNfYFyiQDT/1sHdc86Fb7CYXvrSKCDHqJ9l9 OSWqCHO0/cYPa3ylDhqf6y820RTSZtL93ba0/jGN1oVlEHjGaHVVykQ3MCU+Z6yj5W Stp2vxGoONL9lIG5qlLIvwPqw495ZXWRGOcbNNcduB2d9QF46/J+RZy3jhW8UW+Yoe 5lypxi/zl4Ku7tZnxaxkw12IeQII5MIXEcGtCs7SxEBmWncna6ityUGGr3As4XirRc zrtFEF64kiJCzQIJjj/FtQi84qhO0pj2g1lozr3UvVSKZgWbxb5zl5K461ANhI+fVX rz+yJMFWSC3+A== Message-ID: <3cc27720-8f53-4b6f-9202-42b3b73928b8@kernel.org> Date: Fri, 9 Jan 2026 15:46:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V4 2/2] mm/khugepaged: retry with sync writeback for MADV_COLLAPSE To: Shivank Garg , Andrew Morton , Lorenzo Stoakes Cc: Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Zach O'Keefe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Branden Moore References: <20251215084615.5283-3-shivankg@amd.com> <20251215084615.5283-7-shivankg@amd.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAa2VybmVsLm9yZz7CwY0EEwEIADcWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaKYhwAIbAwUJJlgIpAILCQQVCgkIAhYCAh4FAheAAAoJEE3eEPcA/4Naa5EP/3a1 9sgS9m7oiR0uenlj+C6kkIKlpWKRfGH/WvtFaHr/y06TKnWn6cMOZzJQ+8S39GOteyCCGADh 6ceBx1KPf6/AvMktnGETDTqZ0N9roR4/aEPSMt8kHu/GKR3gtPwzfosX2NgqXNmA7ErU4puf zica1DAmTvx44LOYjvBV24JQG99bZ5Bm2gTDjGXV15/X159CpS6Tc2e3KvYfnfRvezD+alhF XIym8OvvGMeo97BCHpX88pHVIfBg2g2JogR6f0PAJtHGYz6M/9YMxyUShJfo0Df1SOMAbU1Q Op0Ij4PlFCC64rovjH38ly0xfRZH37DZs6kP0jOj4QdExdaXcTILKJFIB3wWXWsqLbtJVgjR YhOrPokd6mDA3gAque7481KkpKM4JraOEELg8pF6eRb3KcAwPRekvf/nYVIbOVyT9lXD5mJn IZUY0LwZsFN0YhGhQJ8xronZy0A59faGBMuVnVb3oy2S0fO1y/r53IeUDTF1wCYF+fM5zo14 5L8mE1GsDJ7FNLj5eSDu/qdZIKqzfY0/l0SAUAAt5yYYejKuii4kfTyLDF/j4LyYZD1QzxLC MjQl36IEcmDTMznLf0/JvCHlxTYZsF0OjWWj1ATRMk41/Q+PX07XQlRCRcE13a8neEz3F6we 08oWh2DnC4AXKbP+kuD9ZP6+5+x1H1zEzsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCgh Cj/CA/lc/LMthqQ773gauB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseB fDXHA6m4B3mUTWo13nid0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts 6TZ+IrPOwT1hfB4WNC+X2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiu Qmt3yqrmN63V9wzaPhC+xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKB Tccu2AXJXWAE1Xjh6GOC8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvF FFyAS0Nk1q/7EChPcbRbhJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh 2YmnmLRTro6eZ/qYwWkCu8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRk F3TwgucpyPtcpmQtTkWSgDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0L LH63+BrrHasfJzxKXzqgrW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4v q7oFCPsOgwARAQABwsF8BBgBCAAmAhsMFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmic2qsF CSZYCKEACgkQTd4Q9wD/g1oq0xAAsAnw/OmsERdtdwRfAMpC74/++2wh9RvVQ0x8xXvoGJwZ rk0Jmck1ABIM//5sWDo7eDHk1uEcc95pbP9XGU6ZgeiQeh06+0vRYILwDk8Q/y06TrTb1n4n 7FRwyskKU1UWnNW86lvWUJuGPABXjrkfL41RJttSJHF3M1C0u2BnM5VnDuPFQKzhRRktBMK4 GkWBvXlsHFhn8Ev0xvPE/G99RAg9ufNAxyq2lSzbUIwrY918KHlziBKwNyLoPn9kgHD3hRBa Yakz87WKUZd17ZnPMZiXriCWZxwPx7zs6cSAqcfcVucmdPiIlyG1K/HIk2LX63T6oO2Libzz 7/0i4+oIpvpK2X6zZ2cu0k2uNcEYm2xAb+xGmqwnPnHX/ac8lJEyzH3lh+pt2slI4VcPNnz+ vzYeBAS1S+VJc1pcJr3l7PRSQ4bv5sObZvezRdqEFB4tUIfSbDdEBCCvvEMBgoisDB8ceYxO cFAM8nBWrEmNU2vvIGJzjJ/NVYYIY0TgOc5bS9wh6jKHL2+chrfDW5neLJjY2x3snF8q7U9G EIbBfNHDlOV8SyhEjtX0DyKxQKioTYPOHcW9gdV5fhSz5tEv+ipqt4kIgWqBgzK8ePtDTqRM qZq457g1/SXSoSQi4jN+gsneqvlTJdzaEu1bJP0iv6ViVf15+qHuY5iojCz8fa0= In-Reply-To: <20251215084615.5283-7-shivankg@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8B1C340013 X-Stat-Signature: d3mkcway5y7t7zjt3gmn1ubec5y7kxiu X-Rspam-User: X-HE-Tag: 1767969995-979471 X-HE-Meta: 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 OARiA3NU iyLJLXjBVvA9JGKGukc0DT4U7focGyiopBQUZ24LYfZWhxtgN295WOFHOBOZtlRQYyCrZguRWsa4cOHd5xpaHBXRRE9yF93Yk7NNnynElTOarUaa2NdaIyMysulCEIdm1OCkkON/js9YFw5/9N6IaBL4mC8pPnVrCGUROKWtWehvcdGgZ4dsjPMmjfzNiCAhS6XE05f0LOg+Vd3Iv21jJ0QTVAzGeAzPEpEz8o/kBYiHkKiDKNqr4kTEXBlAAiarwPQCHx6EX6A2FvW/0ms9SdzgTMUi3iH5WpHelzFJw/ylyxH1jbf/54MgBjbpVzJOns+0EwD//KpC+xn4AWugqr/82Q1ulUwazmku+GFWnMK/t7yjnC9Ke+rNVNjTrt9MrSEwQ 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 12/15/25 09:46, Shivank Garg wrote: > When MADV_COLLAPSE is called on file-backed mappings (e.g., executable > text sections), the pages may still be dirty from recent writes. > collapse_file() will trigger async writeback and fail with > SCAN_PAGE_DIRTY_OR_WRITEBACK (-EAGAIN). > > MADV_COLLAPSE is a synchronous operation where userspace expects > immediate results. 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 > Tested-by: Lance Yang > Signed-off-by: Shivank Garg > --- > mm/khugepaged.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 219dfa2e523c..6c8c35d3e0c9 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: Jumping into an if block is nasty :) > cond_resched(); > mmap_read_lock(mm); > mmap_locked = true; > @@ -2819,6 +2822,43 @@ 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; > + } > + } > + This looks a bit complicated. Can't we move that handing up, where we have most of that information already? Or am I missing something important? diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 97d1b2824386f..c7271877c5220 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include "internal.h" @@ -2786,7 +2787,9 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { int result = SCAN_FAIL; + bool triggered_wb = false; +retry: if (!mmap_locked) { cond_resched(); mmap_read_lock(mm); @@ -2809,6 +2812,16 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, mmap_locked = false; result = hpage_collapse_scan_file(mm, addr, file, pgoff, cc); + + 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; + + filemap_write_and_wait_range(file->f_mapping, lstart, lend); + triggered_wb = true; + goto retry; + } fput(file); } else { result = hpage_collapse_scan_pmd(mm, vma, addr, -- Cheers David