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memcgroup: reinstate swapoff mod

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This patch reinstates the "swapoff: scan ptes preemptibly" mod we started
with: in due course it should be rendered down into the earlier patches,
leaving us with a more straightforward mem_cgroup_charge mod to unuse_pte,
allocating with GFP_KERNEL while holding no spinlock and no atomic kmap.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: David Rientjes <rientjes@google.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2008-02-07 00:14:04 -08:00 committed by Linus Torvalds
parent 3062fc67da
commit 044d66c1d2
1 changed files with 34 additions and 8 deletions
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42
mm/swapfile.c
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@ -507,11 +507,23 @@ unsigned int count_swap_pages(int type, int free)
* just let do_wp_page work it out if a write is requested later - to
* force COW, vm_page_prot omits write permission from any private vma.
*/
static int unuse_pte(struct vm_area_struct *vma, pte_t *pte,
static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, swp_entry_t entry, struct page *page)
{
spinlock_t *ptl;
pte_t *pte;
int ret = 1;
if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
return -ENOMEM;
ret = -ENOMEM;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
if (ret > 0)
mem_cgroup_uncharge_page(page);
ret = 0;
goto out;
}
inc_mm_counter(vma->vm_mm, anon_rss);
get_page(page);
@ -524,7 +536,9 @@ static int unuse_pte(struct vm_area_struct *vma, pte_t *pte,
* immediately swapped out again after swapon.
*/
activate_page(page);
return 1;
out:
pte_unmap_unlock(pte, ptl);
return ret;
}
static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
@ -533,21 +547,33 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
{
pte_t swp_pte = swp_entry_to_pte(entry);
pte_t *pte;
spinlock_t *ptl;
int ret = 0;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
/*
* We don't actually need pte lock while scanning for swp_pte: since
* we hold page lock and mmap_sem, swp_pte cannot be inserted into the
* page table while we're scanning; though it could get zapped, and on
* some architectures (e.g. x86_32 with PAE) we might catch a glimpse
* of unmatched parts which look like swp_pte, so unuse_pte must
* recheck under pte lock. Scanning without pte lock lets it be
* preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
*/
pte = pte_offset_map(pmd, addr);
do {
/*
* swapoff spends a _lot_ of time in this loop!
* Test inline before going to call unuse_pte.
*/
if (unlikely(pte_same(*pte, swp_pte))) {
ret = unuse_pte(vma, pte++, addr, entry, page);
break;
pte_unmap(pte);
ret = unuse_pte(vma, pmd, addr, entry, page);
if (ret)
goto out;
pte = pte_offset_map(pmd, addr);
}
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap_unlock(pte - 1, ptl);
pte_unmap(pte - 1);
out:
return ret;
}