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GET /api/patches/2216648/?format=api
{ "id": 2216648, "url": "http://patchwork.ozlabs.org/api/patches/2216648/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260327021403.214713-16-usama.arif@linux.dev/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/", "list_archive_url_format": "https://lore.kernel.org/linuxppc-dev/{}/", "commit_url_format": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id={}" }, "msgid": "<20260327021403.214713-16-usama.arif@linux.dev>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260327021403.214713-16-usama.arif@linux.dev/", "date": "2026-03-27T02:08:57", "name": "[v3,15/24] fs/dax: handle split_huge_pmd failure in dax_iomap_pmd_fault", "commit_ref": null, "pull_url": null, "state": "handled-elsewhere", "archived": false, "hash": "1acdcd8d27298392f6c1949626b90fe1fd644112", "submitter": { "id": 92719, "url": "http://patchwork.ozlabs.org/api/people/92719/?format=api", "name": "Usama Arif", "email": "usama.arif@linux.dev" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260327021403.214713-16-usama.arif@linux.dev/mbox/", "series": [ { "id": 497678, "url": "http://patchwork.ozlabs.org/api/series/497678/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=497678", "date": "2026-03-27T02:08:43", "name": "[v3,01/24] mm: thp: make split_huge_pmd functions return int for error propagation", "version": 3, "mbox": "http://patchwork.ozlabs.org/series/497678/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2216648/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2216648/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-18858-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linuxppc-dev@lists.ozlabs.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=Hnot0p5K;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1774577763; c=relaxed/relaxed;\n\tbh=8tx/Qjve1iVx/sjsNymGDpKKmMZv1TUyDs/EfcYY5GE=;\n\th=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References:\n\t MIME-Version;\n b=R74Lq4UfkN3uh4yRBTZmuWQsUCWWclvti25DWucA1F4DX4FaZYDCnWgQ0sp8CMW0CWIyoUMFQJ+ZCDjmFCWc55IO5HvdGN+eJQJmM7VfSNH04hfUvMo/17Kt0zND2Mk6p3rtYv7nBW8MMexrOsNxWw+6uat+5IpJdtt7Rv3X3BRf1pxAwl/Z9X7BeHQ75v6/gzPla0TWFXLZvVw3ZPwmAh4NMIRNXpR0Z6akvScT5VqNwd2k+875EwkHRO5QaNNvApblyMoO5ur12jtcTlCpcRoElg1XzaZNYKh+wxvmpa88ChCwvRZcOmMEVYy7DCbzIrnSafiSRCszmE9Lo9cAFA==", "ARC-Authentication-Results": "i=1; lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev; dkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=Hnot0p5K; dkim-atps=neutral;\n spf=pass (client-ip=2001:41d0:1004:224b::ae; helo=out-174.mta0.migadu.com;\n envelope-from=usama.arif@linux.dev;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.dev", "X-Report-Abuse": "Please report any abuse attempt to abuse@migadu.com and\n include these headers.", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1;\n\tt=1774577743;\n\th=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n\t to:to:cc:cc:mime-version:mime-version:\n\t content-transfer-encoding:content-transfer-encoding:\n\t in-reply-to:in-reply-to:references:references;\n\tbh=8tx/Qjve1iVx/sjsNymGDpKKmMZv1TUyDs/EfcYY5GE=;\n\tb=Hnot0p5K89CAv1AQSFPCVNypjXRfAocNMIZyWJnznY4gpq+GWy2CVy+0V7yyIEu0F+HuLG\n\tVCDbIV/SqybnVZSHtV9JQkcdTWMzMp9IQ8Hs+qWemVt0yevh5Dk4OIgO/2Wqfo3fp+W2Sb\n\taJvabR1V9LfLrBzcx+XgaoHKYXMXuJs=", "From": "Usama Arif <usama.arif@linux.dev>", "To": "Andrew Morton <akpm@linux-foundation.org>,\n\tdavid@kernel.org,\n\tLorenzo Stoakes <ljs@kernel.org>,\n\twilly@infradead.org,\n\tlinux-mm@kvack.org", "Cc": "fvdl@google.com,\n\thannes@cmpxchg.org,\n\triel@surriel.com,\n\tshakeel.butt@linux.dev,\n\tkas@kernel.org,\n\tbaohua@kernel.org,\n\tdev.jain@arm.com,\n\tbaolin.wang@linux.alibaba.com,\n\tnpache@redhat.com,\n\tLiam.Howlett@oracle.com,\n\tryan.roberts@arm.com,\n\tVlastimil Babka <vbabka@kernel.org>,\n\tlance.yang@linux.dev,\n\tlinux-kernel@vger.kernel.org,\n\tkernel-team@meta.com,\n\tmaddy@linux.ibm.com,\n\tmpe@ellerman.id.au,\n\tlinuxppc-dev@lists.ozlabs.org,\n\thca@linux.ibm.com,\n\tgor@linux.ibm.com,\n\tagordeev@linux.ibm.com,\n\tborntraeger@linux.ibm.com,\n\tsvens@linux.ibm.com,\n\tlinux-s390@vger.kernel.org,\n\tUsama Arif <usama.arif@linux.dev>", "Subject": "[v3 15/24] fs/dax: handle split_huge_pmd failure in\n dax_iomap_pmd_fault", "Date": "Thu, 26 Mar 2026 19:08:57 -0700", "Message-ID": "<20260327021403.214713-16-usama.arif@linux.dev>", "In-Reply-To": "<20260327021403.214713-1-usama.arif@linux.dev>", "References": "<20260327021403.214713-1-usama.arif@linux.dev>", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-Migadu-Flow": "FLOW_OUT", "X-Spam-Status": "No, score=-0.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_PASS,SPF_PASS autolearn=disabled\n\tversion=4.0.1 OzLabs 8", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "dax_iomap_pmd_fault() splits a huge PMD when the PMD fault falls back\nto PTE-level handling. The split is necessary so that the subsequent\nPTE fault does not misinterpret the huge PMD entry as a page table\npointer.\n\nIn practice this cannot fail today: DAX VMAs are always file-backed,\nand __split_huge_pmd() only allocates a PTE page table (the operation\nthat can return -ENOMEM) for anonymous VMAs. For file-backed VMAs the\nsplit path simply zaps the PMD and returns 0.\n\nUse WARN_ON_ONCE to document this invariant and check the return value\nfor __must_check compliance introduced in the next patch.\n\nSigned-off-by: Usama Arif <usama.arif@linux.dev>\n---\n fs/dax.c | 9 ++++++++-\n 1 file changed, 8 insertions(+), 1 deletion(-)", "diff": "diff --git a/fs/dax.c b/fs/dax.c\nindex a5237169b4679..ed1859e8a916f 100644\n--- a/fs/dax.c\n+++ b/fs/dax.c\n@@ -2039,7 +2039,14 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, unsigned long *pfnp,\n \tdax_unlock_entry(&xas, entry);\n fallback:\n \tif (ret == VM_FAULT_FALLBACK) {\n-\t\tsplit_huge_pmd(vmf->vma, vmf->pmd, vmf->address);\n+\t\t/*\n+\t\t * split_huge_pmd() cannot fail for file-backed (DAX) VMAs\n+\t\t * since splitting only zaps the PMD without allocating a\n+\t\t * PTE page table.\n+\t\t */\n+\t\tif (WARN_ON_ONCE(split_huge_pmd(vmf->vma, vmf->pmd,\n+\t\t\t\t\t\tvmf->address)))\n+\t\t\tret = VM_FAULT_OOM;\n \t\tcount_vm_event(THP_FAULT_FALLBACK);\n \t}\n out:\n", "prefixes": [ "v3", "15/24" ] }