From: Ben LaHaise <bcrl@redhat.com>
To: Andrea Arcangeli <andrea@suse.de>
Cc: riel@nl.linux.org, Linus Torvalds <torvalds@transmeta.com>,
linux-mm@kvack.org
Subject: [patch] take 2 Re: PG_swap_entry bug in recent kernels
Date: Thu, 6 Apr 2000 18:11:43 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.21.0004061802080.6583-100000@devserv.devel.redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.21.0004041915290.1653-100000@alpha.random>
On Tue, 4 Apr 2000, Andrea Arcangeli wrote:
> Could you explain me how acquire_swap_entry() can return an invalid swap
> entry (starting with a random page->index of course)? I can't exclude
> there's a bug, but acquire_swap_entry was meant to return only valid
> entries despite of the page->index possible garbage and it seems it's
> doing that.
First off, it doesn't verify that all of the bits which should be clear in
a swap entry actually are -- eg bit 0 (present) can and is getting
set. It would have to rebuild and compare the swap entry produced by
SWP_ENTRY(type,offset) to be 100% sure that it is a valid swap entry.
And yes, I see what you're doing with the PG_swap_entry code now, although
I'm thinking it might be better done by taking a look at what swap entries
are present in the page tables near the page (since otherwise a pair of
fork()ed process could end up splitting contiguous swap entries if the
swapout is timed just right). But that's for later...
> >As well as from shrink_mmap.
>
> I would not be complaining your patch if you would put the clear_bit
> within shrink_mmap :).
Heheh, okay I've moved it there. Just in case I've also added a
BUG() check in free_pages_okay to make sure there aren't any other places
that have been missed.
-ben
diff -ur 2.3.99-pre4-4/mm/filemap.c linux-test/mm/filemap.c
--- 2.3.99-pre4-4/mm/filemap.c Thu Apr 6 15:03:05 2000
+++ linux-test/mm/filemap.c Thu Apr 6 17:50:39 2000
@@ -300,6 +300,7 @@
if (PageSwapCache(page)) {
spin_unlock(&pagecache_lock);
__delete_from_swap_cache(page);
+ ClearPageSwapEntry(page);
goto made_inode_progress;
}
diff -ur 2.3.99-pre4-4/mm/page_alloc.c linux-test/mm/page_alloc.c
--- 2.3.99-pre4-4/mm/page_alloc.c Thu Apr 6 15:03:05 2000
+++ linux-test/mm/page_alloc.c Thu Apr 6 17:38:10 2000
@@ -110,6 +110,8 @@
BUG();
if (PageDecrAfter(page))
BUG();
+ if (PageSwapEntry(page))
+ BUG();
zone = page->zone;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux.eu.org/Linux-MM/
next prev parent reply other threads:[~2000-04-06 22:11 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-04-03 22:22 PG_swap_entry bug in recent kernels Ben LaHaise
2000-04-04 15:06 ` Andrea Arcangeli
2000-04-04 15:46 ` Rik van Riel
2000-04-04 16:50 ` Andrea Arcangeli
2000-04-04 17:06 ` Ben LaHaise
2000-04-04 18:03 ` Andrea Arcangeli
2000-04-06 22:11 ` Ben LaHaise [this message]
2000-04-07 10:45 ` [patch] take 2 " Andrea Arcangeli
2000-04-07 11:29 ` Rik van Riel
2000-04-07 12:00 ` Andrea Arcangeli
2000-04-07 12:54 ` Rik van Riel
2000-04-07 13:14 ` Andrea Arcangeli
2000-04-07 20:12 ` Kanoj Sarcar
2000-04-07 23:26 ` Andrea Arcangeli
2000-04-08 0:11 ` Kanoj Sarcar
2000-04-08 0:37 ` Kanoj Sarcar
2000-04-08 13:20 ` Andrea Arcangeli
2000-04-08 21:39 ` Kanoj Sarcar
2000-04-08 23:02 ` Andrea Arcangeli
2000-04-08 23:18 ` Kanoj Sarcar
2000-04-08 23:58 ` Andrea Arcangeli
2000-04-08 13:30 ` Andrea Arcangeli
2000-04-08 17:39 ` Andrea Arcangeli
2000-04-07 23:54 ` Andrea Arcangeli
2000-04-08 0:15 ` Kanoj Sarcar
2000-04-08 13:14 ` Andrea Arcangeli
2000-04-08 21:47 ` Kanoj Sarcar
2000-04-08 23:10 ` Andrea Arcangeli
2000-04-08 23:21 ` Kanoj Sarcar
2000-04-08 23:39 ` Andrea Arcangeli
2000-04-09 0:40 ` Kanoj Sarcar
2000-04-10 8:55 ` andrea
2000-04-11 2:45 ` Kanoj Sarcar
2000-04-11 16:22 ` Andrea Arcangeli
2000-04-11 17:40 ` Rik van Riel
2000-04-11 18:20 ` Kanoj Sarcar
2000-04-21 18:23 ` Andrea Arcangeli
2000-04-21 21:00 ` Rik van Riel
2000-04-22 1:12 ` Andrea Arcangeli
2000-04-22 1:51 ` Linus Torvalds
2000-04-22 18:29 ` Rik van Riel
2000-04-22 19:58 ` Linus Torvalds
2000-04-11 18:26 ` Kanoj Sarcar
2000-04-10 19:10 ` Stephen C. Tweedie
2000-04-08 0:04 ` Andrea Arcangeli
[not found] <yttem7xstk2.fsf@vexeta.dc.fi.udc.es>
2000-04-23 0:52 ` Andrea Arcangeli
[not found] <yttk8ho26s8.fsf@vexeta.dc.fi.udc.es>
2000-04-23 16:07 ` Andrea Arcangeli
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=Pine.LNX.4.21.0004061802080.6583-100000@devserv.devel.redhat.com \
--to=bcrl@redhat.com \
--cc=andrea@suse.de \
--cc=linux-mm@kvack.org \
--cc=riel@nl.linux.org \
--cc=torvalds@transmeta.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: link
Be 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.