diff options
author | Hugh Dickins <hugh@veritas.com> | 2008-02-07 00:14:04 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-07 08:42:19 -0800 |
commit | 044d66c1d2b1c5aa50b4d6d68c21c6c93dd678da (patch) | |
tree | 35442e01a5ef7e2d45abc20d45122c3c4c809d5d /mm | |
parent | 3062fc67dad01b1d2a15d58c709eff946389eca4 (diff) | |
download | linux-next-044d66c1d2b1c5aa50b4d6d68c21c6c93dd678da.tar.gz |
memcgroup: reinstate swapoff mod
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>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/swapfile.c | 42 |
1 files changed, 34 insertions, 8 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 35e00c3d0286..02ccab5ad9d9 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -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; } |