From: David Hildenbrand <david@redhat.com> To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, "David Hildenbrand" <david@redhat.com>, "Andrew Morton" <akpm@linux-foundation.org>, "Michal Hocko" <mhocko@suse.com>, "Vlastimil Babka" <vbabka@suse.cz>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, "Matthew Wilcox" <mawilcox@microsoft.com>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Huang Ying" <ying.huang@intel.com>, "Pavel Tatashin" <pasha.tatashin@oracle.com>, "Miles Chen" <miles.chen@mediatek.com>, "Dave Young" <dyoung@redhat.com>, "Baoquan He" <bhe@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, "Petr Tesarik" <ptesarik@suse.cz> Subject: [PATCH v1 1/2] mm: clarify semantics of reserved pages Date: Fri, 20 Jul 2018 14:34:21 +0200 [thread overview] Message-ID: <20180720123422.10127-2-david@redhat.com> (raw) In-Reply-To: <20180720123422.10127-1-david@redhat.com> The reserved bit once was used to hinder pages from getting swapped. While this still works, the semantics are a little bit stronger nowadays: The page should never be touched by anybody in the system except by the owner. The original comment already gave a hint about that. So especially, these pages should also not be dumped by dumping tools. Let's make that more clear by updating the comment. This will be useful especially in the future in virtual environments where pages marked with the reserved bit might no longer be accessible. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: David Hildenbrand <david@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com> Cc: Petr Tesarik <ptesarik@suse.cz> Signed-off-by: David Hildenbrand <david@redhat.com> --- include/linux/page-flags.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 901943e4754b..ba81e11a868c 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -17,8 +17,8 @@ /* * Various page->flags bits: * - * PG_reserved is set for special pages, which can never be swapped out. Some - * of them might not even exist... + * PG_reserved is set for special pages, which should never be touched (read/ + * write) by anybody except their owner. Some of them might not even exist. * * The PG_private bitflag is set on pagecache pages if they contain filesystem * specific data (which is normally at page->private). It can be used by -- 2.17.1
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com> To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, "David Hildenbrand" <david@redhat.com>, "Andrew Morton" <akpm@linux-foundation.org>, "Michal Hocko" <mhocko@suse.com>, "Vlastimil Babka" <vbabka@suse.cz>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, "Matthew Wilcox" <mawilcox@microsoft.com>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Huang Ying" <ying.huang@intel.com>, "Pavel Tatashin" <pasha.tatashin@oracle.com>, "Miles Chen" <miles.chen@mediatek.com>, "Dave Young" <dyoung@redhat.com>, "Baoquan He" <bhe@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, "Petr Tesarik" <ptesarik@suse.cz> Subject: [PATCH v1 1/2] mm: clarify semantics of reserved pages Date: Fri, 20 Jul 2018 14:34:21 +0200 [thread overview] Message-ID: <20180720123422.10127-2-david@redhat.com> (raw) In-Reply-To: <20180720123422.10127-1-david@redhat.com> The reserved bit once was used to hinder pages from getting swapped. While this still works, the semantics are a little bit stronger nowadays: The page should never be touched by anybody in the system except by the owner. The original comment already gave a hint about that. So especially, these pages should also not be dumped by dumping tools. Let's make that more clear by updating the comment. This will be useful especially in the future in virtual environments where pages marked with the reserved bit might no longer be accessible. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: David Hildenbrand <david@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Pavel Tatashin <pasha.tatashin@oracle.com> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Marc-AndrA(C) Lureau" <marcandre.lureau@redhat.com> Cc: Petr Tesarik <ptesarik@suse.cz> Signed-off-by: David Hildenbrand <david@redhat.com> --- include/linux/page-flags.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 901943e4754b..ba81e11a868c 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -17,8 +17,8 @@ /* * Various page->flags bits: * - * PG_reserved is set for special pages, which can never be swapped out. Some - * of them might not even exist... + * PG_reserved is set for special pages, which should never be touched (read/ + * write) by anybody except their owner. Some of them might not even exist. * * The PG_private bitflag is set on pagecache pages if they contain filesystem * specific data (which is normally at page->private). It can be used by -- 2.17.1
next prev parent reply other threads:[~2018-07-20 12:34 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-20 12:34 [PATCH v1 0/2] mm/kdump: exclude reserved pages in dumps David Hildenbrand 2018-07-20 12:34 ` David Hildenbrand [this message] 2018-07-20 12:34 ` [PATCH v1 1/2] mm: clarify semantics of reserved pages David Hildenbrand 2018-07-23 10:48 ` Michal Hocko 2018-07-23 10:48 ` Michal Hocko 2018-07-20 12:34 ` [PATCH v1 2/2] kdump: include PG_reserved value in VMCOREINFO David Hildenbrand 2018-07-23 11:45 ` [PATCH v1 0/2] mm/kdump: exclude reserved pages in dumps Vlastimil Babka 2018-07-23 12:30 ` Michal Hocko 2018-07-23 17:20 ` David Hildenbrand 2018-07-24 7:25 ` Michal Hocko 2018-07-24 8:46 ` David Hildenbrand 2018-07-24 8:53 ` Michal Hocko 2018-07-24 9:18 ` David Hildenbrand 2018-07-24 12:17 ` David Hildenbrand 2018-07-24 13:13 ` Michal Hocko 2018-07-24 13:27 ` David Hildenbrand 2018-07-24 13:35 ` Michal Hocko 2018-07-24 14:13 ` David Hildenbrand 2018-07-25 13:51 ` Michal Hocko 2018-07-25 14:20 ` David Hildenbrand 2018-07-26 8:27 ` Michal Hocko 2018-07-26 8:37 ` David Hildenbrand 2018-07-24 9:47 ` Vlastimil Babka 2018-07-24 11:19 ` Michal Hocko 2018-07-24 12:22 ` Vlastimil Babka 2018-07-24 12:33 ` David Hildenbrand 2018-07-24 13:06 ` Michal Hocko 2018-07-23 17:12 ` David Hildenbrand 2018-07-24 7:22 ` Michal Hocko 2018-07-24 9:48 ` Vlastimil Babka 2018-07-26 8:22 ` David Hildenbrand 2018-07-26 8:30 ` Michal Hocko 2018-07-26 8:45 ` David Hildenbrand 2018-07-26 19:50 ` Andrew Morton 2018-07-30 8:17 ` David Hildenbrand
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20180720123422.10127-2-david@redhat.com \ --to=david@redhat.com \ --cc=akpm@linux-foundation.org \ --cc=bhe@redhat.com \ --cc=dyoung@redhat.com \ --cc=gregkh@linuxfoundation.org \ --cc=kirill.shutemov@linux.intel.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=marcandre.lureau@redhat.com \ --cc=mawilcox@microsoft.com \ --cc=mhocko@suse.com \ --cc=miles.chen@mediatek.com \ --cc=pasha.tatashin@oracle.com \ --cc=ptesarik@suse.cz \ --cc=vbabka@suse.cz \ --cc=ying.huang@intel.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.