From 7e7f774984cd88c45c18e7ffaf0256c3e9118043 Mon Sep 17 00:00:00 2001 From: Ross Zwisler Date: Fri, 22 Jan 2016 15:10:44 -0800 Subject: [PATCH] mm: add find_get_entries_tag() Add find_get_entries_tag() to the family of functions that include find_get_entries(), find_get_pages() and find_get_pages_tag(). This is needed for DAX dirty page handling because we need a list of both page offsets and radix tree entries ('indices' and 'entries' in this function) that are marked with the PAGECACHE_TAG_TOWRITE tag. Signed-off-by: Ross Zwisler Reviewed-by: Jan Kara Cc: "H. Peter Anvin" Cc: "J. Bruce Fields" Cc: "Theodore Ts'o" Cc: Alexander Viro Cc: Andreas Dilger Cc: Dave Chinner Cc: Ingo Molnar Cc: Jeff Layton Cc: Matthew Wilcox Cc: Thomas Gleixner Cc: Dan Williams Cc: Matthew Wilcox Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pagemap.h | 3 ++ mm/filemap.c | 68 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 4d08b6c33557..92395a0a7dc5 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -361,6 +361,9 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start, unsigned int nr_pages, struct page **pages); unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, int tag, unsigned int nr_pages, struct page **pages); +unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, + int tag, unsigned int nr_entries, + struct page **entries, pgoff_t *indices); struct page *grab_cache_page_write_begin(struct address_space *mapping, pgoff_t index, unsigned flags); diff --git a/mm/filemap.c b/mm/filemap.c index 7b8be78cfd9e..1e215fc36c83 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1499,6 +1499,74 @@ repeat: } EXPORT_SYMBOL(find_get_pages_tag); +/** + * find_get_entries_tag - find and return entries that match @tag + * @mapping: the address_space to search + * @start: the starting page cache index + * @tag: the tag index + * @nr_entries: the maximum number of entries + * @entries: where the resulting entries are placed + * @indices: the cache indices corresponding to the entries in @entries + * + * Like find_get_entries, except we only return entries which are tagged with + * @tag. + */ +unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, + int tag, unsigned int nr_entries, + struct page **entries, pgoff_t *indices) +{ + void **slot; + unsigned int ret = 0; + struct radix_tree_iter iter; + + if (!nr_entries) + return 0; + + rcu_read_lock(); +restart: + radix_tree_for_each_tagged(slot, &mapping->page_tree, + &iter, start, tag) { + struct page *page; +repeat: + page = radix_tree_deref_slot(slot); + if (unlikely(!page)) + continue; + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) { + /* + * Transient condition which can only trigger + * when entry at index 0 moves out of or back + * to root: none yet gotten, safe to restart. + */ + goto restart; + } + + /* + * A shadow entry of a recently evicted page, a swap + * entry from shmem/tmpfs or a DAX entry. Return it + * without attempting to raise page count. + */ + goto export; + } + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } +export: + indices[ret] = iter.index; + entries[ret] = page; + if (++ret == nr_entries) + break; + } + rcu_read_unlock(); + return ret; +} +EXPORT_SYMBOL(find_get_entries_tag); + /* * CD/DVDs are error prone. When a medium error occurs, the driver may fail * a _large_ part of the i/o request. Imagine the worst scenario: -- 2.20.1