Btrfs: don't release pages when we can't clear the uptodate bits

[pandora-kernel.git] / fs / btrfs / extent_io.c

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 6411ed6..e7aeba2 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1920,6 +1920,8 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree,
                nr = bio_get_nr_vecs(bdev);
 
        bio = btrfs_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
+       if (!bio)
+               return -ENOMEM;
 
        bio_add_page(bio, page, page_size, offset);
        bio->bi_end_io = end_io_func;
@@ -1944,6 +1946,7 @@ void set_page_extent_mapped(struct page *page)
 
 static void set_page_extent_head(struct page *page, unsigned long len)
 {
+       WARN_ON(!PagePrivate(page));
        set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
 }
 
@@ -2819,9 +2822,17 @@ int try_release_extent_state(struct extent_map_tree *map,
                 * at this point we can safely clear everything except the
                 * locked bit and the nodatasum bit
                 */
-               clear_extent_bit(tree, start, end,
+               ret = clear_extent_bit(tree, start, end,
                                 ~(EXTENT_LOCKED | EXTENT_NODATASUM),
                                 0, 0, NULL, mask);
+
+               /* if clear_extent_bit failed for enomem reasons,
+                * we can't allow the release to continue.
+                */
+               if (ret < 0)
+                       ret = 0;
+               else
+                       ret = 1;
        }
        return ret;
 }
@@ -3193,7 +3204,13 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
                }
                if (!PageUptodate(p))
                        uptodate = 0;
-               unlock_page(p);
+
+               /*
+                * see below about how we avoid a nasty race with release page
+                * and why we unlock later
+                */
+               if (i != 0)
+                       unlock_page(p);
        }
        if (uptodate)
                set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
@@ -3217,9 +3234,26 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
        atomic_inc(&eb->refs);
        spin_unlock(&tree->buffer_lock);
        radix_tree_preload_end();
+
+       /*
+        * there is a race where release page may have
+        * tried to find this extent buffer in the radix
+        * but failed.  It will tell the VM it is safe to
+        * reclaim the, and it will clear the page private bit.
+        * We must make sure to set the page private bit properly
+        * after the extent buffer is in the radix tree so
+        * it doesn't get lost
+        */
+       set_page_extent_mapped(eb->first_page);
+       set_page_extent_head(eb->first_page, eb->len);
+       if (!page0)
+               unlock_page(eb->first_page);
        return eb;
 
 free_eb:
+       if (eb->first_page && !page0)
+               unlock_page(eb->first_page);
+
        if (!atomic_dec_and_test(&eb->refs))
                return exists;
        btrfs_release_extent_buffer(eb);
@@ -3270,10 +3304,11 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
                        continue;
 
                lock_page(page);
+               WARN_ON(!PagePrivate(page));
+
+               set_page_extent_mapped(page);
                if (i == 0)
                        set_page_extent_head(page, eb->len);
-               else
-                       set_page_private(page, EXTENT_PAGE_PRIVATE);
 
                clear_page_dirty_for_io(page);
                spin_lock_irq(&page->mapping->tree_lock);
@@ -3463,6 +3498,13 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
 
        for (i = start_i; i < num_pages; i++) {
                page = extent_buffer_page(eb, i);
+
+               WARN_ON(!PagePrivate(page));
+
+               set_page_extent_mapped(page);
+               if (i == 0)
+                       set_page_extent_head(page, eb->len);
+
                if (inc_all_pages)
                        page_cache_get(page);
                if (!PageUptodate(page)) {