Commit 56f31801 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

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: default avatarHugh 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9e16b7fb

mm/memory.c

+8 −10
Original line number Diff line number Diff line
@@ -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)

{

	spinlock_t *ptl;

	struct page *page, *swapcache = NULL;

	struct page *page, *swapcache;

	swp_entry_t entry;

	pte_t pte;

	int locked;
@@ -3005,9 +3005,11 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		 */

		ret = VM_FAULT_HWPOISON;

		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

		swapcache = page;

		goto out_release;

	}



	swapcache = page;

	locked = lock_page_or_retry(page, mm, flags);



	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))

		goto out_page;



	swapcache = page;

	page = ksm_might_need_to_copy(page, vma, address);

	if (unlikely(!page)) {

		ret = VM_FAULT_OOM;

		page = swapcache;

		swapcache = NULL;

		goto out_page;

	}

	if (page == swapcache)

		swapcache = NULL;



	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {

		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);

	set_pte_at(mm, address, page_table, pte);

	if (swapcache) /* ksm created a completely new copy */

		page_add_new_anon_rmap(page, vma, address);

	else

	if (page == swapcache)

		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 */

	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))

		try_to_free_swap(page);

	unlock_page(page);

	if (swapcache) {

	if (page != swapcache) {

		/*

		 * Hold the lock to avoid the swap entry to be reused

		 * until we take the PT lock for the pte_same() check
@@ -3122,7 +3120,7 @@ out_page: 
	unlock_page(page);

out_release:

	page_cache_release(page);

	if (swapcache) {

	if (page != swapcache) {

		unlock_page(swapcache);

		page_cache_release(swapcache);

	}

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