mm: refactor do_wp_page - rewrite the unlock flow (28766805) · Commits · 戴 / test

When do_wp_page is ending, in several cases it needs to unlock the pages and ptls it was accessing. Currently, this logic was "called" by using a goto jump. This makes following the control flow of the function harder. Readability was further hampered by the unlock case containing large amount of logic needed only in one of the 3 cases. Using goto for cleanup is generally allowed. However, moving the trivial unlocking flows to the relevant call sites allow deeper refactoring in the next patch. Signed-off-by:

Shachar Raindel <raindel@mellanox.com> Acked-by:

Linus Torvalds <torvalds@linux-foundation.org> Acked-by:

Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by:

Rik van Riel <riel@redhat.com> Acked-by:

Andi Kleen <ak@linux.intel.com> Acked-by:

Haggai Eran <haggaie@mellanox.com> Acked-by:

Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Peter Feiner <pfeiner@google.com> Cc: Michel Lespinasse <walken@google.com> Reviewed-by:

Michal Hocko <mhocko@suse.cz> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -2066,7 +2066,7 @@ static int do_wp_page(struct mm_struct mm, struct vm_area_struct vma,
		{
		struct page old_page, new_page = NULL;
		pte_t entry;
		int ret = 0;
		int page_copied = 0;
		unsigned long mmun_start = 0; /* For mmu_notifiers */
		unsigned long mmun_end = 0; /* For mmu_notifiers */
		struct mem_cgroup *memcg;
		@@ -2101,7 +2101,9 @@ static int do_wp_page(struct mm_struct mm, struct vm_area_struct vma,
		&ptl);
		if (!pte_same(*page_table, orig_pte)) {
		unlock_page(old_page);
		goto unlock;
		pte_unmap_unlock(page_table, ptl);
		page_cache_release(old_page);
		return 0;
		}
		page_cache_release(old_page);
		}
		@@ -2148,7 +2150,9 @@ static int do_wp_page(struct mm_struct mm, struct vm_area_struct vma,
		&ptl);
		if (!pte_same(*page_table, orig_pte)) {
		unlock_page(old_page);
		goto unlock;
		pte_unmap_unlock(page_table, ptl);
		page_cache_release(old_page);
		return 0;
		}
		page_mkwrite = 1;
		}
		@@ -2246,29 +2250,28 @@ gotten:

		/* Free the old page.. */
		new_page = old_page;
		ret \|= VM_FAULT_WRITE;
		page_copied = 1;
		} else
		mem_cgroup_cancel_charge(new_page, memcg);

		if (new_page)
		page_cache_release(new_page);
		unlock:

		pte_unmap_unlock(page_table, ptl);
		if (mmun_end > mmun_start)
		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
		if (old_page) {
		/*
		* Don't let another task, with possibly unlocked vma,
		* keep the mlocked page.
		*/
		if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
		if (page_copied && (vma->vm_flags & VM_LOCKED)) {
		lock_page(old_page); /* LRU manipulation */
		munlock_vma_page(old_page);
		unlock_page(old_page);
		}
		page_cache_release(old_page);
		}
		return ret;
		return page_copied ? VM_FAULT_WRITE : 0;
		oom_free_new:
		page_cache_release(new_page);
		oom:

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