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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pIyl8-002RNk-SW; Fri, 20 Jan 2023 21:17:14 +0000 Date: Fri, 20 Jan 2023 21:17:14 +0000 From: Matthew Wilcox To: Sidhartha Kumar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, songmuchun@bytedance.com, mike.kravetz@oracle.com, jhubbard@nvidia.com Subject: Re: [PATCH 4/9] mm/rmap: change hugepage_add_new_anon_rmap to take in a folio Message-ID: References: <20230119211446.54165-1-sidhartha.kumar@oracle.com> <20230119211446.54165-5-sidhartha.kumar@oracle.com> <9c276d01-379f-9bd7-0a7a-6a831b7b4571@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9c276d01-379f-9bd7-0a7a-6a831b7b4571@oracle.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D07811C001A X-Stat-Signature: b8zieoxfhonraht3q53t1n6cbyggk3wm X-HE-Tag: 1674249445-94552 X-HE-Meta: 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 BGzVBOif HhX4ja90ZTtD5d7bKlJSOjJSUM771/Sk4Mpe98gkZUGpHmNv5+R1nlnTPiVjbzZWhlN4i2m9H0NpBcKcCNMHFimPa0HP4eH/JM7r60WlRHKROLc2+/fmUbF1fFsVCjgbVTL5T+qIzeXz0aJaELO5xsLB3p5kZ0DT2GMwTKg4B9qL2cVEfFz/dIl4ife8SG6wEARxkW96xUXUkExg= 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: On Fri, Jan 20, 2023 at 12:45:38PM -0800, Sidhartha Kumar wrote: > > > @@ -6176,6 +6186,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > > > spinlock_t *ptl; > > > int ret = -ENOMEM; > > > struct page *page; > > > + struct folio *folio = NULL; > > > int writable; > > > bool page_in_pagecache = false; > > > @@ -6251,12 +6262,15 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > > > *pagep = NULL; > > > } > > > + if (page) > > > + folio = page_folio(page); > > > + > > > /* > > > - * The memory barrier inside __SetPageUptodate makes sure that > > > + * The memory barrier inside __folio_mark_uptodate makes sure that > > > * preceding stores to the page contents become visible before > > > * the set_pte_at() write. > > > */ > > > - __SetPageUptodate(page); > > > + __folio_mark_uptodate(folio); > > > > Hi Matthew, > > In the snippet: > > page = alloc_huge_page(dst_vma, dst_addr, 0); > if (IS_ERR(page)) { > put_page(*pagep); > ret = -ENOMEM; > *pagep = NULL; > goto out; > } > copy_user_huge_page(page, *pagep, dst_addr, dst_vma, > pages_per_huge_page(h)); > > I thought the IS_ERR() call does not handle the NULL case and is a check for > high memory addresses, and copy_user_huge_page() path does not seem to > handle the NULL case as well but alloc_huge_page() can possibly return NULL > so I was unsure about how to handle the folio conversion. I'm not sure how alloc_huge_page() can return NULL. It seems like it returns ERR_PTR(-ENOSPC) or ERR_PTR(-ENOMEM) if it cannot allocate memory?