From: Dave McCracken <dmccr@us.ibm.com>
To: Andrew Morton <akpm@digeo.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 2.5.63] Make objrmap mapcount non-atomic
Date: Tue, 04 Mar 2003 12:32:11 -0600 [thread overview]
Message-ID: <30210000.1046802731@baldur.austin.ibm.com> (raw)
In-Reply-To: <20030303141518.12d9ccd8.akpm@digeo.com>
[-- Attachment #1: Type: text/plain, Size: 815 bytes --]
--On Monday, March 03, 2003 14:15:18 -0800 Andrew Morton <akpm@digeo.com>
wrote:
> Well why not make mapcount an "int" and move the places where it is
> modified inside pte_chain_lock()?
>
> That does not increase the number of atomic operations, and it makes me
> stop wondering if this:
>
> if (atomic_read(&page->pte.mapcount) == 0)
> inc_page_state(nr_mapped);
>
> is racy ;)
That would be entirely too easy a solution :)
You're entirely right, of course. Here's the patch that makes it an int
instead of atomic, with the appropriate locking.
Dave
======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
dmccr@us.ibm.com T/L 678-3059
[-- Attachment #2: objfix-2.5.63-2.diff --]
[-- Type: text/plain, Size: 2270 bytes --]
--- 2.5.63-objrmap/./include/linux/mm.h 2003-02-27 15:58:34.000000000 -0600
+++ 2.5.63-objfix/./include/linux/mm.h 2003-03-03 16:26:21.000000000 -0600
@@ -172,7 +172,7 @@
struct pte_chain *chain;/* Reverse pte mapping pointer.
* protected by PG_chainlock */
pte_addr_t direct;
- atomic_t mapcount;
+ int mapcount;
} pte;
unsigned long private; /* mapping-private opaque data */
--- 2.5.63-objrmap/./mm/rmap.c 2003-02-28 14:19:10.000000000 -0600
+++ 2.5.63-objfix/./mm/rmap.c 2003-03-03 20:08:43.000000000 -0600
@@ -144,7 +144,7 @@
struct vm_area_struct *vma;
int referenced = 0;
- if (atomic_read(&page->pte.mapcount) == 0)
+ if (!page->pte.mapcount)
return 0;
if (!mapping)
@@ -243,19 +243,20 @@
if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
return pte_chain;
+ pte_chain_lock(page);
+
if (!PageAnon(page)) {
if (!page->mapping)
BUG();
if (PageSwapCache(page))
BUG();
- if (atomic_read(&page->pte.mapcount) == 0)
+ if (!page->pte.mapcount)
inc_page_state(nr_mapped);
- atomic_inc(&page->pte.mapcount);
+ page->pte.mapcount++;
+ pte_chain_unlock(page);
return pte_chain;
}
- pte_chain_lock(page);
-
#ifdef DEBUG_RMAP
/*
* This stuff needs help to get up to highmem speed.
@@ -342,20 +343,22 @@
if (!page_mapped(page))
return; /* remap_page_range() from a driver? */
+ pte_chain_lock(page);
+
if (!PageAnon(page)) {
if (!page->mapping)
BUG();
if (PageSwapCache(page))
BUG();
- if (atomic_read(&page->pte.mapcount) == 0)
+ if (!page->pte.mapcount)
BUG();
- if (atomic_dec_and_test(&page->pte.mapcount))
+ page->pte.mapcount--;
+ if (!page->pte.mapcount)
dec_page_state(nr_mapped);
+ pte_chain_unlock(page);
return;
}
- pte_chain_lock(page);
-
if (PageDirect(page)) {
if (page->pte.direct == pte_paddr) {
page->pte.direct = 0;
@@ -471,11 +474,11 @@
if (pte_dirty(pteval))
set_page_dirty(page);
- if (atomic_read(&page->pte.mapcount) == 0)
+ if (!page->pte.mapcount)
BUG();
mm->rss--;
- atomic_dec(&page->pte.mapcount);
+ page->pte.mapcount--;
page_cache_release(page);
out_unmap:
@@ -516,7 +519,7 @@
goto out;
}
- if (atomic_read(&page->pte.mapcount) != 0)
+ if (page->pte.mapcount)
BUG();
out:
next prev parent reply other threads:[~2003-03-04 18:21 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-27 10:59 2.5.63-mm1 Andrew Morton
2003-02-27 21:22 ` Rising io_load results 2.5.63-mm1 Con Kolivas
2003-02-27 21:44 ` Andrew Morton
2003-02-27 22:01 ` Dave McCracken
2003-02-27 22:24 ` Andrew Morton
2003-03-03 21:06 ` [PATCH 2.5.63] Teach page_mapped about the anon flag Dave McCracken
2003-03-03 21:12 ` Andrew Morton
2003-03-03 21:24 ` Dave McCracken
2003-03-03 21:35 ` Andrew Morton
2003-03-03 21:52 ` Dave McCracken
2003-03-03 22:15 ` Andrew Morton
2003-03-04 18:32 ` Dave McCracken [this message]
2003-02-27 23:56 ` Rising io_load results Re: 2.5.63-mm1 Con Kolivas
2003-02-28 0:06 ` Andrew Morton
2003-02-28 0:28 ` Con Kolivas
2003-02-28 7:46 ` Duncan Sands
2003-02-28 8:06 ` Andrew Morton
2003-02-28 12:48 ` Hugh Dickins
2003-02-28 15:56 ` Dave McCracken
2003-02-28 0:17 ` 2.5.63-mm1 Ed Tomlinson
2003-02-28 0:46 ` 2.5.63-mm1 Andrew Morton
2003-02-28 12:16 ` 2.5.63-mm1 steven roemen
2003-02-28 12:24 ` 2.5.63-mm1 Andrew Morton
[not found] ` <3E5F7DAD.2080306@cyberone.com.au>
[not found] ` <200302282227.56311.tomlins@cam.org>
2003-03-01 15:04 ` [PATCH] tiobench on UP and ptg-D3-mm1 Ed Tomlinson
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=30210000.1046802731@baldur.austin.ibm.com \
--to=dmccr@us.ibm.com \
--cc=akpm@digeo.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.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).