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[80.193.200.194]) by smtp.googlemail.com with ESMTPSA id h29-20020adfaa9d000000b0020c5253d913sm11597769wrc.95.2022.05.04.06.36.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 May 2022 06:36:37 -0700 (PDT) Message-ID: <9a206b6b-bb60-b86b-666d-c75748237cf0@gmail.com> Date: Wed, 4 May 2022 14:36:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Content-Language: en-US To: Andrew Morton , Linux-MM , Hugh Dickins , "Matthew Wilcox (Oracle)" From: "Colin King (gmail)" Subject: re: mm/shmem: turn shmem_alloc_page() into shmem_alloc_folio() Cc: "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7C43240082 X-Stat-Signature: 11d5rrysfq1dtasxt7hzkqy35od6zuqu Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=fRnO9sm5; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf11.hostedemail.com: domain of colin.i.king@gmail.com designates 209.85.221.41 as permitted sender) smtp.mailfrom=colin.i.king@gmail.com X-Rspam-User: X-HE-Tag: 1651671395-441216 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: Hi, Static analysis with clang scan-build found an issue in the following commit: commit b0bb08b2d5f399369a906eff0287e64b531881d8 Author: Matthew Wilcox (Oracle) Date: Fri Apr 29 14:43:02 2022 -0700 mm/shmem: turn shmem_alloc_page() into shmem_alloc_folio() The issue is as follows: #ifdef CONFIG_USERFAULTFD int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr, unsigned long src_addr, bool zeropage, bool wp_copy, struct page **pagep) { struct inode *inode = file_inode(dst_vma->vm_file); struct shmem_inode_info *info = SHMEM_I(inode); struct address_space *mapping = inode->i_mapping; gfp_t gfp = mapping_gfp_mask(mapping); pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); void *page_kaddr; struct folio *folio; struct page *page; ^^ page is not intialized int ret; pgoff_t max_off; if (!shmem_inode_acct_block(inode, 1)) { /* * We may have got a page, returned -ENOENT triggering a retry, * and now we find ourselves with -ENOMEM. Release the page, to * avoid a BUG_ON in our caller. */ if (unlikely(*pagep)) { put_page(*pagep); *pagep = NULL; } return -ENOMEM; } if (!*pagep) { ret = -ENOMEM; if (!page) goto out_unacct_blocks; ^^ page is being referenced but it has not been set The commit in question removed the assignment to page: if (!*pagep) { ret = -ENOMEM; - page = shmem_alloc_page(gfp, info, pgoff); if (!page) goto out_unacct_blocks; Colin