mm: write_cache_pages early loop termination

[pandora-kernel.git] / mm / page-writeback.c

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2970e35..01b9cb8 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -868,9 +868,11 @@ int write_cache_pages(struct address_space *mapping,
        int done = 0;
        struct pagevec pvec;
        int nr_pages;
+       pgoff_t uninitialized_var(writeback_index);
        pgoff_t index;
        pgoff_t end;            /* Inclusive */
-       int scanned = 0;
+       pgoff_t done_index;
+       int cycled;
        int range_whole = 0;
        long nr_to_write = wbc->nr_to_write;
 
@@ -881,26 +883,33 @@ int write_cache_pages(struct address_space *mapping,
 
        pagevec_init(&pvec, 0);
        if (wbc->range_cyclic) {
-               index = mapping->writeback_index; /* Start from prev offset */
+               writeback_index = mapping->writeback_index; /* prev offset */
+               index = writeback_index;
+               if (index == 0)
+                       cycled = 1;
+               else
+                       cycled = 0;
                end = -1;
        } else {
                index = wbc->range_start >> PAGE_CACHE_SHIFT;
                end = wbc->range_end >> PAGE_CACHE_SHIFT;
                if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
                        range_whole = 1;
-               scanned = 1;
+               cycled = 1; /* ignore range_cyclic tests */
        }
 retry:
+       done_index = index;
        while (!done && (index <= end) &&
               (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
                                              PAGECACHE_TAG_DIRTY,
                                              min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
                unsigned i;
 
-               scanned = 1;
                for (i = 0; i < nr_pages; i++) {
                        struct page *page = pvec.pages[i];
 
+                       done_index = page->index + 1;
+
                        /*
                         * At this point we hold neither mapping->tree_lock nor
                         * lock on the page itself: the page may be truncated or
@@ -915,7 +924,11 @@ retry:
                                continue;
                        }
 
-                       if (!wbc->range_cyclic && page->index > end) {
+                       if (page->index > end) {
+                               /*
+                                * can't be range_cyclic (1st pass) because
+                                * end == -1 in that case.
+                                */
                                done = 1;
                                unlock_page(page);
                                continue;
@@ -946,18 +959,20 @@ retry:
                pagevec_release(&pvec);
                cond_resched();
        }
-       if (!scanned && !done) {
+       if (!cycled) {
                /*
+                * range_cyclic:
                 * We hit the last page and there is more work to be done: wrap
                 * back to the start of the file
                 */
-               scanned = 1;
+               cycled = 1;
                index = 0;
+               end = writeback_index - 1;
                goto retry;
        }
        if (!wbc->no_nrwrite_index_update) {
                if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
-                       mapping->writeback_index = index;
+                       mapping->writeback_index = done_index;
                wbc->nr_to_write = nr_to_write;
        }