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mm: cleanup "swapcache" in do_swap_page 

I dislike the way in which "swapcache" gets used in do_swap_page():
there is always a page from swapcache there (even if maybe uncached by
the time we lock it), but tests are made according to "swapcache".
Rework that with "page != swapcache", as has been done in unuse_pte().

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Petr Holasek <pholasek@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Izik Eidus <izik.eidus@ravellosystems.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
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 2013-02-22 16:36:10 -08:00 committed by Linus Torvalds
parent 9e16b7fb1d
commit 56f31801cc
1 changed files with 8 additions and 10 deletions
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18
mm/memory.c
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@ -2954,7 +2954,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned int flags, pte_t orig_pte) unsigned int flags, pte_t orig_pte)
{ {
spinlock_t *ptl; spinlock_t *ptl;
struct page *page, *swapcache = NULL; struct page *page, *swapcache;
swp_entry_t entry; swp_entry_t entry;
pte_t pte; pte_t pte;
int locked; int locked;
@ -3005,9 +3005,11 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/ */
ret = VM_FAULT_HWPOISON; ret = VM_FAULT_HWPOISON;
delayacct_clear_flag(DELAYACCT_PF_SWAPIN); delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
swapcache = page;
goto out_release; goto out_release;
} }
swapcache = page;
locked = lock_page_or_retry(page, mm, flags); locked = lock_page_or_retry(page, mm, flags);
delayacct_clear_flag(DELAYACCT_PF_SWAPIN); delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
@ -3025,16 +3027,12 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val)) if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
goto out_page; goto out_page;
swapcache = page;
page = ksm_might_need_to_copy(page, vma, address); page = ksm_might_need_to_copy(page, vma, address);
if (unlikely(!page)) { if (unlikely(!page)) {
ret = VM_FAULT_OOM; ret = VM_FAULT_OOM;
page = swapcache; page = swapcache;
swapcache = NULL;
goto out_page; goto out_page;
} }
if (page == swapcache)
swapcache = NULL;
if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) { if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
ret = VM_FAULT_OOM; ret = VM_FAULT_OOM;
@ -3078,10 +3076,10 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
} }
flush_icache_page(vma, page); flush_icache_page(vma, page);
set_pte_at(mm, address, page_table, pte); set_pte_at(mm, address, page_table, pte);
if (swapcache) /* ksm created a completely new copy */ if (page == swapcache)
page_add_new_anon_rmap(page, vma, address);
else
do_page_add_anon_rmap(page, vma, address, exclusive); do_page_add_anon_rmap(page, vma, address, exclusive);
else /* ksm created a completely new copy */
page_add_new_anon_rmap(page, vma, address);
/* It's better to call commit-charge after rmap is established */ /* It's better to call commit-charge after rmap is established */
mem_cgroup_commit_charge_swapin(page, ptr); mem_cgroup_commit_charge_swapin(page, ptr);
@ -3089,7 +3087,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
try_to_free_swap(page); try_to_free_swap(page);
unlock_page(page); unlock_page(page);
if (swapcache) { if (page != swapcache) {
/* /*
* Hold the lock to avoid the swap entry to be reused * Hold the lock to avoid the swap entry to be reused
* until we take the PT lock for the pte_same() check * until we take the PT lock for the pte_same() check
@ -3122,7 +3120,7 @@ out_page:
unlock_page(page); unlock_page(page);
out_release: out_release:
page_cache_release(page); page_cache_release(page);
if (swapcache) { if (page != swapcache) {
unlock_page(swapcache); unlock_page(swapcache);
page_cache_release(swapcache); page_cache_release(swapcache);
} }