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Fri, 22 Mar 2024 11:05:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id JnoXKRNm/WUhZgAAD6G6ig (envelope-from ); Fri, 22 Mar 2024 11:05:55 +0000 Message-ID: Date: Fri, 22 Mar 2024 12:05:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 8/9] mm: Improve dumping of mapcount and page_type Content-Language: en-US To: "Matthew Wilcox (Oracle)" , Andrew Morton Cc: linux-mm@kvack.org, David Hildenbrand , Miaohe Lin , Muchun Song , Oscar Salvador References: <20240321142448.1645400-1-willy@infradead.org> <20240321142448.1645400-9-willy@infradead.org> From: Vlastimil Babka In-Reply-To: <20240321142448.1645400-9-willy@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8F1E840014 X-Stat-Signature: 3ww5r4u9y1gjztgkr5km4m16cotocu5t X-HE-Tag: 1711105557-188653 X-HE-Meta: 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 eSDl0UHN fCvNoYx2NUQCecYU= 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 3/21/24 15:24, Matthew Wilcox (Oracle) wrote: > For pages that have a page_type, set the mapcount to 0, which will > reduce the confusion in people reading page dumps ("Why does this page > have a mapcount of -128?"). Now that hugetlbfs is a page_type, read the > entire_mapcount for any large folio; this is fine for all folios as no > user reuses the entire_mapcount field. > > For pages which do not have a page type, do not print it to reduce > clutter. > > Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Vlastimil Babka > --- > mm/debug.c | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > diff --git a/mm/debug.c b/mm/debug.c > index c1c1a6a484e4..e8a96b8b7197 100644 > --- a/mm/debug.c > +++ b/mm/debug.c > @@ -55,18 +55,14 @@ static void __dump_folio(struct folio *folio, struct page *page, > unsigned long pfn, unsigned long idx) > { > struct address_space *mapping = folio_mapping(folio); > - int mapcount = 0; > + int mapcount = atomic_read(&page->_mapcount) + 1; > char *type = ""; > > - /* > - * page->_mapcount space in struct page is used by slab pages to > - * encode own info, and we must avoid calling page_folio() again. > - */ > - if (!folio_test_slab(folio)) { > - mapcount = atomic_read(&page->_mapcount) + 1; > - if (folio_test_large(folio)) > - mapcount += folio_entire_mapcount(folio); > - } > + /* Open-code page_mapcount() to avoid looking up a stale folio */ > + if (mapcount < 0) > + mapcount = 0; > + if (folio_test_large(folio)) > + mapcount += folio_entire_mapcount(folio); > > pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", > folio_ref_count(folio), mapcount, mapping, > @@ -99,7 +95,8 @@ static void __dump_folio(struct folio *folio, struct page *page, > */ > pr_warn("%sflags: %pGp%s\n", type, &folio->flags, > is_migrate_cma_folio(folio, pfn) ? " CMA" : ""); > - pr_warn("page_type: %pGt\n", &folio->page.page_type); > + if (page_has_type(&folio->page)) > + pr_warn("page_type: %pGt\n", &folio->page.page_type); > > print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32, > sizeof(unsigned long), page,