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mm: no get_user/put_user while holding mmap_sem in do_pages_stat?

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Since commit 2f007e74bb, do_pages_stat()
gets the page address from user-space and puts the corresponding status
back while holding the mmap_sem for read.  There is no need to hold
mmap_sem there while some page-faults may occur.

This patch adds a temporary address and status buffer so as to only
hold mmap_sem while working on these kernel buffers.  This is
implemented by extracting do_pages_stat_array() out of do_pages_stat().

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Brice Goglin 2008-12-09 13:14:23 -08:00 committed by Linus Torvalds
parent 52b9582dd5
commit 80bba1290a
1 changed files with 46 additions and 13 deletions
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59
mm/migrate.c
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@ -987,25 +987,18 @@ out:
/*
* Determine the nodes of an array of pages and store it in an array of status.
*/
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
const void __user * __user *pages,
int __user *status)
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
const void __user **pages, int *status)
{
unsigned long i;
int err;
down_read(&mm->mmap_sem);
for (i = 0; i < nr_pages; i++) {
const void __user *p;
unsigned long addr;
unsigned long addr = (unsigned long)(*pages);
struct vm_area_struct *vma;
struct page *page;
err = -EFAULT;
if (get_user(p, pages+i))
goto out;
addr = (unsigned long) p;
int err;
vma = find_vma(mm, addr);
if (!vma)
@ -1024,12 +1017,52 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
err = page_to_nid(page);
set_status:
put_user(err, status+i);
*status = err;
pages++;
status++;
}
up_read(&mm->mmap_sem);
}
/*
* Determine the nodes of a user array of pages and store it in
* a user array of status.
*/
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
const void __user * __user *pages,
int __user *status)
{
#define DO_PAGES_STAT_CHUNK_NR 16
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
int chunk_status[DO_PAGES_STAT_CHUNK_NR];
unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR;
int err;
for (i = 0; i < nr_pages; i += chunk_nr) {
if (chunk_nr + i > nr_pages)
chunk_nr = nr_pages - i;
err = copy_from_user(chunk_pages, &pages[i],
chunk_nr * sizeof(*chunk_pages));
if (err) {
err = -EFAULT;
goto out;
}
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
err = copy_to_user(&status[i], chunk_status,
chunk_nr * sizeof(*chunk_status));
if (err) {
err = -EFAULT;
goto out;
}
}
err = 0;
out:
up_read(&mm->mmap_sem);
return err;
}