mm/shmem: return head page from find_lock_entry (63ec1973) · Commits · 戴 / test

include/linux/pagemap.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -372,6 +372,15 @@ static inline struct page grab_cache_page_nowait(struct address_space mapping,
		mapping_gfp_mask(mapping));
		}

		/* Does this page contain this index? */
		static inline bool thp_contains(struct page *head, pgoff_t index)
		{
		/* HugeTLBfs indexes the page cache in units of hpage_size */
		if (PageHuge(head))
		return head->index == index;
		return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
		}

		/*
		* Given the page we found in the page cache, return the page corresponding
		* to this index in the file

mm/filemap.c

+11 −14

Original line number	Diff line number	Diff line
		@@ -1692,37 +1692,34 @@ out:
		}

		/**
		* find_lock_entry - locate, pin and lock a page cache entry
		* @mapping: the address_space to search
		* @offset: the page cache index
		* find_lock_entry - Locate and lock a page cache entry.
		* @mapping: The address_space to search.
		* @index: The page cache index.
		*
		* Looks up the page cache slot at @mapping & @offset. If there is a
		* page cache page, it is returned locked and with an increased
		* refcount.
		* Looks up the page at @mapping & @index. If there is a page in the
		* cache, the head page is returned locked and with an increased refcount.
		*
		* If the slot holds a shadow entry of a previously evicted page, or a
		* swap entry from shmem/tmpfs, it is returned.
		*
		* find_lock_entry() may sleep.
		*
		* Return: the found page or shadow entry, %NULL if nothing is found.
		* Context: May sleep.
		* Return: The head page or shadow entry, %NULL if nothing is found.
		*/
		struct page find_lock_entry(struct address_space mapping, pgoff_t offset)
		struct page find_lock_entry(struct address_space mapping, pgoff_t index)
		{
		struct page *page;

		repeat:
		page = find_get_entry(mapping, offset);
		page = find_get_entry(mapping, index);
		if (page && !xa_is_value(page)) {
		lock_page(page);
		/* Has the page been truncated? */
		if (unlikely(page_mapping(page) != mapping)) {
		if (unlikely(page->mapping != mapping)) {
		unlock_page(page);
		put_page(page);
		goto repeat;
		}
		page = find_subpage(page, offset);
		VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
		VM_BUG_ON_PAGE(!thp_contains(page, index), page);
		}
		return page;
		}

mm/shmem.c

+10 −9

Original line number	Diff line number	Diff line
		@@ -1830,6 +1830,8 @@ repeat:
		return error;
		}

		if (page)
		hindex = page->index;
		if (page && sgp == SGP_WRITE)
		mark_page_accessed(page);

		@@ -1840,11 +1842,10 @@ repeat:
		unlock_page(page);
		put_page(page);
		page = NULL;
		hindex = index;
		}
		if (page \|\| sgp == SGP_READ) {
		*pagep = page;
		return 0;
		}
		if (page \|\| sgp == SGP_READ)
		goto out;

		/*
		* Fast cache lookup did not find it:
		@@ -1969,14 +1970,13 @@ clear:
		* it now, lest undo on failure cancel our earlier guarantee.
		*/
		if (sgp != SGP_WRITE && !PageUptodate(page)) {
		struct page *head = compound_head(page);
		int i;

		for (i = 0; i < compound_nr(head); i++) {
		clear_highpage(head + i);
		flush_dcache_page(head + i);
		for (i = 0; i < compound_nr(page); i++) {
		clear_highpage(page + i);
		flush_dcache_page(page + i);
		}
		SetPageUptodate(head);
		SetPageUptodate(page);
		}

		/* Perhaps the file has been truncated since we checked */
		@@ -1992,6 +1992,7 @@ clear:
		error = -EINVAL;
		goto unlock;
		}
		out:
		*pagep = page + index - hindex;
		return 0;

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