radix-tree: use iterators in find_get_pages* functions
Replace radix_tree_gang_lookup_slot() and
radix_tree_gang_lookup_tag_slot() in page-cache lookup functions with
brand-new radix-tree direct iterating. This avoids the double-scanning
and pointer copying.
Iterator don't stop after nr_pages page-get fails in a row, it continue
lookup till the radix-tree end. Thus we can safely remove these restart
conditions.
Unfortunately, old implementation didn't forbid nr_pages == 0, this corner
case does not fit into new code, so the patch adds an extra check at the
beginning.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index c3811bc..79c4b2b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -813,20 +813,19 @@
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
unsigned int nr_pages, struct page **pages)
{
- unsigned int i;
- unsigned int ret;
- unsigned int nr_found, nr_skip;
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
rcu_read_lock();
restart:
- nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
- (void ***)pages, NULL, start, nr_pages);
- ret = 0;
- nr_skip = 0;
- for (i = 0; i < nr_found; i++) {
+ radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *page;
repeat:
- page = radix_tree_deref_slot((void **)pages[i]);
+ page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
@@ -837,7 +836,7 @@
* when entry at index 0 moves out of or back
* to root: none yet gotten, safe to restart.
*/
- WARN_ON(start | i);
+ WARN_ON(iter.index);
goto restart;
}
/*
@@ -845,7 +844,6 @@
* here as an exceptional entry: so skip over it -
* we only reach this from invalidate_mapping_pages().
*/
- nr_skip++;
continue;
}
@@ -853,21 +851,16 @@
goto repeat;
/* Has the page moved? */
- if (unlikely(page != *((void **)pages[i]))) {
+ if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
pages[ret] = page;
- ret++;
+ if (++ret == nr_pages)
+ break;
}
- /*
- * If all entries were removed before we could secure them,
- * try again, because callers stop trying once 0 is returned.
- */
- if (unlikely(!ret && nr_found > nr_skip))
- goto restart;
rcu_read_unlock();
return ret;
}
@@ -887,21 +880,22 @@
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
unsigned int nr_pages, struct page **pages)
{
- unsigned int i;
- unsigned int ret;
- unsigned int nr_found;
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned int ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
rcu_read_lock();
restart:
- nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
- (void ***)pages, NULL, index, nr_pages);
- ret = 0;
- for (i = 0; i < nr_found; i++) {
+ radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
struct page *page;
repeat:
- page = radix_tree_deref_slot((void **)pages[i]);
+ page = radix_tree_deref_slot(slot);
+ /* The hole, there no reason to continue */
if (unlikely(!page))
- continue;
+ break;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
@@ -924,7 +918,7 @@
goto repeat;
/* Has the page moved? */
- if (unlikely(page != *((void **)pages[i]))) {
+ if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
@@ -934,14 +928,14 @@
* otherwise we can get both false positives and false
* negatives, which is just confusing to the caller.
*/
- if (page->mapping == NULL || page->index != index) {
+ if (page->mapping == NULL || page->index != iter.index) {
page_cache_release(page);
break;
}
pages[ret] = page;
- ret++;
- index++;
+ if (++ret == nr_pages)
+ break;
}
rcu_read_unlock();
return ret;
@@ -962,19 +956,20 @@
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
int tag, unsigned int nr_pages, struct page **pages)
{
- unsigned int i;
- unsigned int ret;
- unsigned int nr_found;
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
rcu_read_lock();
restart:
- nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
- (void ***)pages, *index, nr_pages, tag);
- ret = 0;
- for (i = 0; i < nr_found; i++) {
+ radix_tree_for_each_tagged(slot, &mapping->page_tree,
+ &iter, *index, tag) {
struct page *page;
repeat:
- page = radix_tree_deref_slot((void **)pages[i]);
+ page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
@@ -998,21 +993,16 @@
goto repeat;
/* Has the page moved? */
- if (unlikely(page != *((void **)pages[i]))) {
+ if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
pages[ret] = page;
- ret++;
+ if (++ret == nr_pages)
+ break;
}
- /*
- * If all entries were removed before we could secure them,
- * try again, because callers stop trying once 0 is returned.
- */
- if (unlikely(!ret && nr_found))
- goto restart;
rcu_read_unlock();
if (ret)