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Date: Tue, 07 Feb 2012 11:55:12 +0400
From: Konstantin Khlebnikov <khlebnikov@...nvz.org>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] radix-tree: use iterators in find_get_pages* functions
This patch replaces 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 pointers copying.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
---
mm/filemap.c | 75 ++++++++++++++++++++++++++++++++++------------------------
mm/shmem.c | 23 +++++++++++-------
2 files changed, 58 insertions(+), 40 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index b662757..518223b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -811,23 +811,25 @@ EXPORT_SYMBOL(find_or_create_page);
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;
+
+ if (!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++) {
+ nr_found = nr_skip = ret = 0;
+ 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;
+ nr_found++;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
/*
@@ -835,7 +837,7 @@ repeat:
* 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;
}
/*
@@ -851,13 +853,14 @@ repeat:
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)
+ goto out;
}
/*
@@ -866,6 +869,7 @@ repeat:
*/
if (unlikely(!ret && nr_found > nr_skip))
goto restart;
+out:
rcu_read_unlock();
return ret;
}
@@ -885,21 +889,23 @@ repeat:
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
unsigned int nr_pages, struct page **pages)
{
- unsigned int i;
+ struct radix_tree_iter iter;
unsigned int ret;
- unsigned int nr_found;
+ void **slot;
+
+ if (!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;
+ goto out;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
@@ -915,14 +921,14 @@ repeat:
* here as an exceptional entry: so stop looking for
* contiguous pages.
*/
- break;
+ goto out;
}
if (!page_cache_get_speculative(page))
goto repeat;
/* Has the page moved? */
- if (unlikely(page != *((void **)pages[i]))) {
+ if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
@@ -932,15 +938,16 @@ repeat:
* 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;
+ goto out;
}
pages[ret] = page;
- ret++;
- index++;
+ if (++ret == nr_pages)
+ goto out;
}
+out:
rcu_read_unlock();
return ret;
}
@@ -960,22 +967,26 @@ EXPORT_SYMBOL(find_get_pages_contig);
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;
+
+ if (!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++) {
+ nr_found = ret = 0;
+ 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;
+ nr_found++;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
/*
@@ -996,13 +1007,14 @@ repeat:
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)
+ goto out;
}
/*
@@ -1011,6 +1023,7 @@ repeat:
*/
if (unlikely(!ret && nr_found))
goto restart;
+out:
rcu_read_unlock();
if (ret)
diff --git a/mm/shmem.c b/mm/shmem.c
index 269d049..5033319 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -316,21 +316,24 @@ static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
pgoff_t start, unsigned int nr_pages,
struct page **pages, pgoff_t *indices)
{
- unsigned int i;
unsigned int ret;
unsigned int nr_found;
+ struct radix_tree_iter iter;
+ void **slot;
+
+ if (!nr_pages)
+ return 0;
rcu_read_lock();
restart:
- nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
- (void ***)pages, indices, start, nr_pages);
- ret = 0;
- for (i = 0; i < nr_found; i++) {
+ nr_found = ret = 0;
+ 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;
+ nr_found++;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page))
goto restart;
@@ -345,17 +348,19 @@ repeat:
goto repeat;
/* Has the page moved? */
- if (unlikely(page != *((void **)pages[i]))) {
+ if (unlikely(page != *slot)) {
page_cache_release(page);
goto repeat;
}
export:
- indices[ret] = indices[i];
+ indices[ret] = iter.index;
pages[ret] = page;
- ret++;
+ if (++ret == nr_pages)
+ goto out;
}
if (unlikely(!ret && nr_found))
goto restart;
+out:
rcu_read_unlock();
return ret;
}
--
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