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Date: Wed, 27 Jan 2016 16:17:51 -0500
From: Matthew Wilcox <matthew.r.wilcox@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>
Cc: Matthew Wilcox <willy@...ux.intel.com>,
Konstantin Khlebnikov <khlebnikov@...nvz.org>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH 4/5] mm: Use radix_tree_iter_retry()
From: Matthew Wilcox <willy@...ux.intel.com>
Instead of a 'goto restart', we can now use radix_tree_iter_retry()
to restart from our current position. This will make a difference
when there are more ways to happen across an indirect pointer. And it
eliminates some confusing gotos.
Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
---
mm/filemap.c | 53 +++++++++++++++++------------------------------------
mm/shmem.c | 18 ++++++++++++------
2 files changed, 29 insertions(+), 42 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 7705dac561ba..e0c4b905fe1c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1245,7 +1245,6 @@ unsigned find_get_entries(struct address_space *mapping,
return 0;
rcu_read_lock();
-restart:
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *page;
repeat:
@@ -1253,8 +1252,10 @@ repeat:
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page))
- goto restart;
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
/*
* A shadow entry of a recently evicted page, a swap
* entry from shmem/tmpfs or a DAX entry. Return it
@@ -1307,7 +1308,6 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
return 0;
rcu_read_lock();
-restart:
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *page;
repeat:
@@ -1317,13 +1317,8 @@ repeat:
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.
- */
- WARN_ON(iter.index);
- goto restart;
+ slot = radix_tree_iter_retry(&iter);
+ continue;
}
/*
* A shadow entry of a recently evicted page,
@@ -1374,7 +1369,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
return 0;
rcu_read_lock();
-restart:
radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
struct page *page;
repeat:
@@ -1385,12 +1379,8 @@ repeat:
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;
+ slot = radix_tree_iter_retry(&iter);
+ continue;
}
/*
* A shadow entry of a recently evicted page,
@@ -1450,7 +1440,6 @@ unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
return 0;
rcu_read_lock();
-restart:
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, *index, tag) {
struct page *page;
@@ -1461,12 +1450,8 @@ repeat:
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;
+ slot = radix_tree_iter_retry(&iter);
+ continue;
}
/*
* A shadow entry of a recently evicted page.
@@ -1529,7 +1514,6 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
return 0;
rcu_read_lock();
-restart:
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, start, tag) {
struct page *page;
@@ -1539,12 +1523,8 @@ repeat:
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;
+ slot = radix_tree_iter_retry(&iter);
+ continue;
}
/*
@@ -2151,10 +2131,11 @@ repeat:
if (unlikely(!page))
goto next;
if (radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page))
- break;
- else
- goto next;
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ goto next;
}
if (!page_cache_get_speculative(page))
diff --git a/mm/shmem.c b/mm/shmem.c
index fa2ceb2d2655..6ec14b70d82d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -388,8 +388,10 @@ restart:
* don't need to reset the counter, nor do we risk infinite
* restarts.
*/
- if (radix_tree_deref_retry(page))
- goto restart;
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
if (radix_tree_exceptional_entry(page))
swapped++;
@@ -1952,8 +1954,10 @@ restart:
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
page = radix_tree_deref_slot(slot);
if (!page || radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page))
- goto restart;
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
} else if (page_count(page) - page_mapcount(page) > 1) {
spin_lock_irq(&mapping->tree_lock);
radix_tree_tag_set(&mapping->page_tree, iter.index,
@@ -2007,8 +2011,10 @@ restart:
page = radix_tree_deref_slot(slot);
if (radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page))
- goto restart;
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
page = NULL;
}
--
2.7.0.rc3
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