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mm: use radix_tree_iter_retry()

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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.

[vbabka@suse.cz: remove now-obsolete-and-misleading comment]
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2016-03-17 14:22:03 -07:00 committed by Linus Torvalds
parent c28f242063
commit 2cf938aae1
2 changed files with 29 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
mm/filemap.c
View File

@ -1255,7 +1255,6 @@ 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:
@ -1263,8 +1262,10 @@ 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
@ -1317,7 +1318,6 @@ 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:
@ -1327,13 +1327,8 @@ 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,
@ -1384,7 +1379,6 @@ 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:
@ -1395,12 +1389,8 @@ 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,
@ -1460,7 +1450,6 @@ 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;
@ -1471,12 +1460,8 @@ 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.
@ -1539,7 +1524,6 @@ 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;
@ -1549,12 +1533,8 @@ 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;
}
/*
@ -2171,10 +2151,11 @@ 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))

23
mm/shmem.c
View File

@ -383,13 +383,10 @@ restart:
page = radix_tree_deref_slot(slot);
/*
* This should only be possible to happen at index 0, so we
* 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++;
@ -1951,8 +1948,10 @@ 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,
@ -2006,8 +2005,10 @@ 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;
}