Btrfs: deal with enomem in the rewind path

We can get ENOMEM trying to allocate dummy bufs for the rewind operation of the
tree mod log.  Instead of BUG_ON()'ing in this case pass up ENOMEM.  I looked
back through the callers and I'm pretty sure I got everybody who did BUG_ON(ret)
in this path.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 74 insertions, 71 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c137f98fbd24..ef25c7d048e2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4222,6 +4222,76 @@ static void __free_extent_buffer(struct extent_buffer *eb)
         kmem_cache_free(extent_buffer_cache, eb);
 }
 
+static int extent_buffer_under_io(struct extent_buffer *eb)
+{
+        return (atomic_read(&eb->io_pages) ||
+                test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
+                test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
+}
+
+/*
+ * Helper for releasing extent buffer page.
+ */
+static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
+                                                unsigned long start_idx)
+{
+        unsigned long index;
+        unsigned long num_pages;
+        struct page *page;
+        int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
+
+        BUG_ON(extent_buffer_under_io(eb));
+
+        num_pages = num_extent_pages(eb->start, eb->len);
+        index = start_idx + num_pages;
+        if (start_idx >= index)
+                return;
+
+        do {
+                index--;
+                page = extent_buffer_page(eb, index);
+                if (page && mapped) {
+                        spin_lock(&page->mapping->private_lock);
+                        /*
+                         * We do this since we'll remove the pages after we've
+                         * removed the eb from the radix tree, so we could race
+                         * and have this page now attached to the new eb.  So
+                         * only clear page_private if it's still connected to
+                         * this eb.
+                         */
+                        if (PagePrivate(page) &&
+                            page->private == (unsigned long)eb) {
+                                BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
+                                BUG_ON(PageDirty(page));
+                                BUG_ON(PageWriteback(page));
+                                /*
+                                 * We need to make sure we haven't be attached
+                                 * to a new eb.
+                                 */
+                                ClearPagePrivate(page);
+                                set_page_private(page, 0);
+                                /* One for the page private */
+                                page_cache_release(page);
+                        }
+                        spin_unlock(&page->mapping->private_lock);
+
+                }
+                if (page) {
+                        /* One for when we alloced the page */
+                        page_cache_release(page);
+                }
+        } while (index != start_idx);
+}
+
+/*
+ * Helper for releasing the extent buffer.
+ */
+static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
+{
+        btrfs_release_extent_buffer_page(eb, 0);
+        __free_extent_buffer(eb);
+}
+
 static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
                                                    u64 start,
                                                    unsigned long len,
@@ -4276,7 +4346,10 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 
         for (i = 0; i < num_pages; i++) {
                 p = alloc_page(GFP_ATOMIC);
-                BUG_ON(!p);
+                if (!p) {
+                        btrfs_release_extent_buffer(new);
+                        return NULL;
+                }
                 attach_extent_buffer_page(new, p);
                 WARN_ON(PageDirty(p));
                 SetPageUptodate(p);
@@ -4317,76 +4390,6 @@ err:
         return NULL;
 }
 
-static int extent_buffer_under_io(struct extent_buffer *eb)
-{
-        return (atomic_read(&eb->io_pages) ||
-                test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
-                test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-}
-
-/*
- * Helper for releasing extent buffer page.
- */
-static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
-                                                unsigned long start_idx)
-{
-        unsigned long index;
-        unsigned long num_pages;
-        struct page *page;
-        int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
-
-        BUG_ON(extent_buffer_under_io(eb));
-
-        num_pages = num_extent_pages(eb->start, eb->len);
-        index = start_idx + num_pages;
-        if (start_idx >= index)
-                return;
-
-        do {
-                index--;
-                page = extent_buffer_page(eb, index);
-                if (page && mapped) {
-                        spin_lock(&page->mapping->private_lock);
-                        /*
-                         * We do this since we'll remove the pages after we've
-                         * removed the eb from the radix tree, so we could race
-                         * and have this page now attached to the new eb.  So
-                         * only clear page_private if it's still connected to
-                         * this eb.
-                         */
-                        if (PagePrivate(page) &&
-                            page->private == (unsigned long)eb) {
-                                BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-                                BUG_ON(PageDirty(page));
-                                BUG_ON(PageWriteback(page));
-                                /*
-                                 * We need to make sure we haven't be attached
-                                 * to a new eb.
-                                 */
-                                ClearPagePrivate(page);
-                                set_page_private(page, 0);
-                                /* One for the page private */
-                                page_cache_release(page);
-                        }
-                        spin_unlock(&page->mapping->private_lock);
-
-                }
-                if (page) {
-                        /* One for when we alloced the page */
-                        page_cache_release(page);
-                }
-        } while (index != start_idx);
-}
-
-/*
- * Helper for releasing the extent buffer.
- */
-static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
-{
-        btrfs_release_extent_buffer_page(eb, 0);
-        __free_extent_buffer(eb);
-}
-
 static void check_buffer_tree_ref(struct extent_buffer *eb)
 {
         int refs;