From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jann Horn <jannh@google.com>
Cc: Jiri Kosina <jikos@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Greg KH <gregkh@linuxfoundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>,
kernel list <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged
Date: Sat, 5 Jan 2019 15:16:32 -0800 [thread overview]
Message-ID: <CAHk-=wg5Kk+r36=jcGBaLUj+gjopjgiW5eyvkdMqvn0jFkD_iQ@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whL4sZiM=JcdQAYQvHm7h7xEtVUh+gYGYhoSk4vi38tXg@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 762 bytes --]
On Sat, Jan 5, 2019 at 3:05 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> That would be nicer than my patch, simply because removing code is
> always nice. And arguably it's a better semantic anyway.
Yeah, I wonder why we did that thing where mincore() walks the page
tables, but if they are empty it looks in the page cache.
[... goes and looks in history ..]
It goes back to forever, it looks like. I can't find a reason.
Anyway, a removal patch would look something like the attached, I
think. That makes mincore() actually say how many pages are in _this_
mapping, not how many pages could be paged in without doing IO.
Hmm. Maybe we should try this first. Simplicity is always good.
Again, obviously untested.
Linus
[-- Attachment #2: patch.diff --]
[-- Type: text/x-patch, Size: 2711 bytes --]
mm/mincore.c | 74 +++++-------------------------------------------------------
1 file changed, 6 insertions(+), 68 deletions(-)
diff --git a/mm/mincore.c b/mm/mincore.c
index 218099b5ed31..317eb64ea4ef 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -42,64 +42,12 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
return 0;
}
-/*
- * Later we can get more picky about what "in core" means precisely.
- * For now, simply check to see if the page is in the page cache,
- * and is up to date; i.e. that no page-in operation would be required
- * at this time if an application were to map and access this page.
- */
-static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
-{
- unsigned char present = 0;
- struct page *page;
-
- /*
- * When tmpfs swaps out a page from a file, any process mapping that
- * file will not get a swp_entry_t in its pte, but rather it is like
- * any other file mapping (ie. marked !present and faulted in with
- * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
- */
-#ifdef CONFIG_SWAP
- if (shmem_mapping(mapping)) {
- page = find_get_entry(mapping, pgoff);
- /*
- * shmem/tmpfs may return swap: account for swapcache
- * page too.
- */
- if (xa_is_value(page)) {
- swp_entry_t swp = radix_to_swp_entry(page);
- page = find_get_page(swap_address_space(swp),
- swp_offset(swp));
- }
- } else
- page = find_get_page(mapping, pgoff);
-#else
- page = find_get_page(mapping, pgoff);
-#endif
- if (page) {
- present = PageUptodate(page);
- put_page(page);
- }
-
- return present;
-}
-
static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
struct vm_area_struct *vma, unsigned char *vec)
{
unsigned long nr = (end - addr) >> PAGE_SHIFT;
- int i;
- if (vma->vm_file) {
- pgoff_t pgoff;
-
- pgoff = linear_page_index(vma, addr);
- for (i = 0; i < nr; i++, pgoff++)
- vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
- } else {
- for (i = 0; i < nr; i++)
- vec[i] = 0;
- }
+ memset(vec, 0, nr);
return nr;
}
@@ -144,21 +92,11 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
else { /* pte is a swap entry */
swp_entry_t entry = pte_to_swp_entry(pte);
- if (non_swap_entry(entry)) {
- /*
- * migration or hwpoison entries are always
- * uptodate
- */
- *vec = 1;
- } else {
-#ifdef CONFIG_SWAP
- *vec = mincore_page(swap_address_space(entry),
- swp_offset(entry));
-#else
- WARN_ON(1);
- *vec = 1;
-#endif
- }
+ /*
+ * migration or hwpoison entries are always
+ * uptodate
+ */
+ *vec = !!non_swap_entry(entry);
}
vec++;
}
next prev parent reply other threads:[~2019-01-05 23:16 UTC|newest]
Thread overview: 161+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-05 17:27 [PATCH] mm/mincore: allow for making sys_mincore() privileged Jiri Kosina
2019-01-05 19:14 ` Vlastimil Babka
2019-01-05 19:24 ` Jiri Kosina
2019-01-05 19:38 ` Vlastimil Babka
2019-01-08 9:14 ` Bernd Petrovitsch
2019-01-08 11:37 ` Jiri Kosina
2019-01-08 13:53 ` Bernd Petrovitsch
2019-01-08 14:08 ` Kirill A. Shutemov
2019-01-05 19:44 ` kbuild test robot
2019-01-05 19:46 ` Linus Torvalds
2019-01-05 20:12 ` Jiri Kosina
2019-01-05 20:17 ` Linus Torvalds
2019-01-05 20:43 ` Jiri Kosina
2019-01-05 21:54 ` Linus Torvalds
2019-01-06 11:33 ` Kevin Easton
2019-01-08 8:50 ` Kevin Easton
2019-01-18 14:23 ` Tejun Heo
2019-01-05 20:13 ` Linus Torvalds
2019-01-05 19:56 ` kbuild test robot
2019-01-05 22:54 ` Jann Horn
2019-01-05 23:05 ` Linus Torvalds
2019-01-05 23:16 ` Linus Torvalds [this message]
2019-01-05 23:28 ` Linus Torvalds
2019-01-05 23:39 ` Linus Torvalds
2019-01-06 0:11 ` Matthew Wilcox
2019-01-06 0:22 ` Linus Torvalds
2019-01-06 1:50 ` Linus Torvalds
2019-01-06 21:46 ` Linus Torvalds
2019-01-08 4:43 ` Dave Chinner
2019-01-08 17:57 ` Linus Torvalds
2019-01-09 2:24 ` Dave Chinner
2019-01-09 2:31 ` Jiri Kosina
2019-01-09 4:39 ` Dave Chinner
2019-01-09 10:08 ` Jiri Kosina
2019-01-10 1:15 ` Dave Chinner
2019-01-10 7:54 ` Jiri Kosina
2019-01-09 18:25 ` Linus Torvalds
2019-01-10 0:44 ` Dave Chinner
2019-01-10 1:18 ` Linus Torvalds
2019-01-10 5:26 ` Andy Lutomirski
2019-01-10 14:47 ` Matthew Wilcox
2019-01-10 21:44 ` Dave Chinner
2019-01-10 21:59 ` Linus Torvalds
2019-01-11 1:47 ` Dave Chinner
2019-01-10 7:03 ` Dave Chinner
2019-01-10 11:47 ` Linus Torvalds
2019-01-10 12:24 ` Dominique Martinet
2019-01-10 22:11 ` Linus Torvalds
2019-01-11 2:03 ` Dave Chinner
2019-01-11 2:18 ` Linus Torvalds
2019-01-11 4:04 ` Dave Chinner
2019-01-11 4:08 ` Andy Lutomirski
2019-01-11 7:20 ` Dave Chinner
2019-01-11 7:08 ` Linus Torvalds
2019-01-11 7:36 ` Dave Chinner
2019-01-11 16:26 ` Linus Torvalds
2019-01-15 23:45 ` Dave Chinner
2019-01-16 4:54 ` Linus Torvalds
2019-01-16 5:49 ` Linus Torvalds
2019-01-17 1:26 ` Dave Chinner
2019-02-20 15:49 ` Nicolai Stange
2019-01-11 4:57 ` Dominique Martinet
2019-01-11 7:11 ` Linus Torvalds
2019-01-11 7:32 ` Dominique Martinet
2019-01-16 0:42 ` Josh Snyder
2019-01-16 5:00 ` Linus Torvalds
2019-01-16 5:25 ` Andy Lutomirski
2019-01-16 5:34 ` Linus Torvalds
2019-01-16 5:46 ` Dominique Martinet
2019-01-16 5:58 ` Linus Torvalds
2019-01-16 6:34 ` Dominique Martinet
2019-01-16 7:52 ` Josh Snyder
2019-01-16 12:18 ` Kevin Easton
2019-01-17 21:45 ` Vlastimil Babka
2019-01-18 4:49 ` Linus Torvalds
2019-01-18 18:58 ` Vlastimil Babka
2019-01-16 16:12 ` Jiri Kosina
2019-01-16 17:48 ` Linus Torvalds
2019-01-16 20:23 ` Jiri Kosina
2019-01-16 21:37 ` Matthew Wilcox
2019-01-16 21:41 ` Jiri Kosina
2019-01-17 9:52 ` Cyril Hrubis
2019-01-28 13:49 ` Cyril Hrubis
2019-01-17 4:51 ` Linus Torvalds
2019-01-18 4:54 ` Linus Torvalds
2019-01-17 1:49 ` Dominique Martinet
2019-01-23 20:27 ` Linus Torvalds
2019-01-23 20:35 ` Linus Torvalds
2019-01-23 23:12 ` Jiri Kosina
2019-01-24 0:20 ` Linus Torvalds
2019-01-24 0:24 ` Dominique Martinet
2019-01-24 12:45 ` Dominique Martinet
2019-01-24 14:25 ` Jiri Kosina
2019-01-27 22:35 ` Jiri Kosina
2019-01-28 0:05 ` Dominique Martinet
2019-01-29 23:52 ` Jiri Kosina
2019-01-30 9:09 ` Michal Hocko
2019-01-30 12:29 ` Jiri Kosina
2019-01-16 12:36 ` Matthew Wilcox
2019-01-10 14:50 ` Matthew Wilcox
2019-01-11 7:36 ` Jiri Kosina
2019-01-17 2:22 ` Dave Chinner
2019-01-17 8:18 ` Jiri Kosina
2019-01-17 21:06 ` Dave Chinner
2019-01-07 4:32 ` Dominique Martinet
2019-01-07 10:33 ` Vlastimil Babka
2019-01-07 11:08 ` Dominique Martinet
2019-01-07 11:59 ` Vlastimil Babka
2019-01-07 13:29 ` Daniel Gruss
2019-01-07 10:10 ` Michael Ellerman
2019-01-05 23:09 ` Jiri Kosina
2019-01-30 12:44 ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Vlastimil Babka
2019-01-30 12:44 ` [PATCH 1/3] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-01-31 9:43 ` Michal Hocko
2019-01-31 9:51 ` Dominique Martinet
2019-01-31 17:46 ` Josh Snyder
2019-02-01 8:56 ` Vlastimil Babka
2019-03-06 23:13 ` Andrew Morton
2019-03-07 0:01 ` Jiri Kosina
2019-03-07 0:40 ` Dominique Martinet
2019-03-07 5:46 ` Jiri Kosina
2019-01-30 12:44 ` [PATCH 2/3] mm/filemap: initiate readahead even if IOCB_NOWAIT is set for the I/O Vlastimil Babka
2019-01-30 15:04 ` Florian Weimer
2019-01-30 15:15 ` Jiri Kosina
2019-01-31 10:47 ` Florian Weimer
2019-01-31 11:34 ` Jiri Kosina
2019-01-31 9:56 ` Michal Hocko
2019-01-31 10:15 ` Jiri Kosina
2019-01-31 10:23 ` Michal Hocko
2019-01-31 10:30 ` Jiri Kosina
2019-01-31 11:32 ` Michal Hocko
2019-01-31 17:54 ` Linus Torvalds
2019-02-01 5:13 ` Dave Chinner
2019-02-01 7:05 ` Linus Torvalds
2019-02-01 7:21 ` Linus Torvalds
2019-02-01 1:44 ` Dave Chinner
2019-02-12 15:48 ` Jiri Kosina
2019-01-31 12:04 ` Daniel Gruss
2019-01-31 12:06 ` Vlastimil Babka
2019-01-31 12:08 ` Jiri Kosina
2019-01-31 12:57 ` Daniel Gruss
2019-01-30 12:44 ` [PATCH 3/3] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka
2019-01-31 10:09 ` Michal Hocko
2019-02-01 9:04 ` Vlastimil Babka
2019-02-01 9:11 ` Michal Hocko
2019-02-01 9:27 ` Vlastimil Babka
2019-02-06 20:14 ` Jiri Kosina
2019-02-12 3:44 ` Jiri Kosina
2019-02-12 6:36 ` Michal Hocko
2019-02-12 13:09 ` Jiri Kosina
2019-02-12 14:01 ` Michal Hocko
2019-03-06 12:11 ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Jiri Kosina
2019-03-06 22:35 ` Andrew Morton
2019-03-06 22:48 ` Jiri Kosina
2019-03-06 23:23 ` Andrew Morton
2019-03-06 23:32 ` Dominique Martinet
2019-03-06 23:38 ` Andrew Morton
2019-03-09 16:53 ` Linus Torvalds
2019-03-12 14:17 ` [PATCH v2 0/2] prevent mincore() page cache leaks Vlastimil Babka
2019-03-12 14:17 ` [PATCH v2 1/2] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-03-12 14:17 ` [PATCH v2 2/2] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka
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='CAHk-=wg5Kk+r36=jcGBaLUj+gjopjgiW5eyvkdMqvn0jFkD_iQ@mail.gmail.com' \
--to=torvalds@linux-foundation.org \
--cc=akpm@linux-foundation.org \
--cc=gregkh@linuxfoundation.org \
--cc=jannh@google.com \
--cc=jikos@kernel.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=peterz@infradead.org \
/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: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).