radix-tree: delete radix_tree_range_tag_if_tagged()
This is an exceptionally complicated function with just one caller
(tag_pages_for_writeback). We devote a large portion of the runtime of
the test suite to testing this one function which has one caller. By
introducing the new function radix_tree_iter_tag_set(), we can eliminate
all of the complexity while keeping the performance. The caller can now
use a fairly standard radix_tree_for_each() loop, and it doesn't need to
worry about tricksy things like 'start' wrapping.
The test suite continues to spend a large amount of time investigating
this function, but now it's testing the underlying primitives such as
radix_tree_iter_resume() and the radix_tree_for_each_tagged() iterator
which are also used by other parts of the kernel.
Link: http://lkml.kernel.org/r/1480369871-5271-57-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 52e2f8e..290e8b7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2106,18 +2106,26 @@
pgoff_t start, pgoff_t end)
{
#define WRITEBACK_TAG_BATCH 4096
- unsigned long tagged;
+ unsigned long tagged = 0;
+ struct radix_tree_iter iter;
+ void **slot;
- do {
- spin_lock_irq(&mapping->tree_lock);
- tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
- &start, end, WRITEBACK_TAG_BATCH,
- PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
+ spin_lock_irq(&mapping->tree_lock);
+ radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, start,
+ PAGECACHE_TAG_DIRTY) {
+ if (iter.index > end)
+ break;
+ radix_tree_iter_tag_set(&mapping->page_tree, &iter,
+ PAGECACHE_TAG_TOWRITE);
+ tagged++;
+ if ((tagged % WRITEBACK_TAG_BATCH) != 0)
+ continue;
+ slot = radix_tree_iter_resume(slot, &iter);
spin_unlock_irq(&mapping->tree_lock);
- WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
cond_resched();
- /* We check 'start' to handle wrapping when end == ~0UL */
- } while (tagged >= WRITEBACK_TAG_BATCH && start);
+ spin_lock_irq(&mapping->tree_lock);
+ }
+ spin_unlock_irq(&mapping->tree_lock);
}
EXPORT_SYMBOL(tag_pages_for_writeback);