ocfs2: Fix extent lookup to return true size of holes

Initially, we had wired things to return a size '1' of holes. Cook up a
small amount of code to find the next extent and calculate the number of
clusters between the virtual offset and the next allocated extent.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 103 insertions, 4 deletions

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index eef6c1887708..f35e04f27f32 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -39,6 +39,97 @@
 #include "buffer_head_io.h"
 
 /*
+ * Return the 1st index within el which contains an extent start
+ * larger than v_cluster.
+ */
+static int ocfs2_search_for_hole_index(struct ocfs2_extent_list *el,
+                                       u32 v_cluster)
+{
+        int i;
+        struct ocfs2_extent_rec *rec;
+
+        for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
+                rec = &el->l_recs[i];
+
+                if (v_cluster < le32_to_cpu(rec->e_cpos))
+                        break;
+        }
+
+        return i;
+}
+
+/*
+ * Figure out the size of a hole which starts at v_cluster within the given
+ * extent list.
+ *
+ * If there is no more allocation past v_cluster, we return the maximum
+ * cluster size minus v_cluster.
+ *
+ * If we have in-inode extents, then el points to the dinode list and
+ * eb_bh is NULL. Otherwise, eb_bh should point to the extent block
+ * containing el.
+ */
+static int ocfs2_figure_hole_clusters(struct inode *inode,
+                                      struct ocfs2_extent_list *el,
+                                      struct buffer_head *eb_bh,
+                                      u32 v_cluster,
+                                      u32 *num_clusters)
+{
+        int ret, i;
+        struct buffer_head *next_eb_bh = NULL;
+        struct ocfs2_extent_block *eb, *next_eb;
+
+        i = ocfs2_search_for_hole_index(el, v_cluster);
+
+        if (i == le16_to_cpu(el->l_next_free_rec) && eb_bh) {
+                eb = (struct ocfs2_extent_block *)eb_bh->b_data;
+
+                /*
+                 * Check the next leaf for any extents.
+                 */
+
+                if (le64_to_cpu(eb->h_next_leaf_blk) == 0ULL)
+                        goto no_more_extents;
+
+                ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
+                                       le64_to_cpu(eb->h_next_leaf_blk),
+                                       &next_eb_bh, OCFS2_BH_CACHED, inode);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+                next_eb = (struct ocfs2_extent_block *)next_eb_bh->b_data;
+
+                if (!OCFS2_IS_VALID_EXTENT_BLOCK(next_eb)) {
+                        ret = -EROFS;
+                        OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, next_eb);
+                        goto out;
+                }
+
+                el = &next_eb->h_list;
+
+                i = ocfs2_search_for_hole_index(el, v_cluster);
+        }
+
+no_more_extents:
+        if (i == le16_to_cpu(el->l_next_free_rec)) {
+                /*
+                 * We're at the end of our existing allocation. Just
+                 * return the maximum number of clusters we could
+                 * possibly allocate.
+                 */
+                *num_clusters = UINT_MAX - v_cluster;
+        } else {
+                *num_clusters = le32_to_cpu(el->l_recs[i].e_cpos) - v_cluster;
+        }
+
+        ret = 0;
+out:
+        brelse(next_eb_bh);
+        return ret;
+}
+
+/*
  * Return the index of the extent record which contains cluster #v_cluster.
  * -1 is returned if it was not found.
  *
@@ -117,11 +208,19 @@ int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
         if (i == -1) {
                 /*
                  * A hole was found. Return some canned values that
-                 * callers can key on.
+                 * callers can key on. If asked for, num_clusters will
+                 * be populated with the size of the hole.
                  */
                 *p_cluster = 0;
-                if (num_clusters)
-                        *num_clusters = 1;
+                if (num_clusters) {
+                        ret = ocfs2_figure_hole_clusters(inode, el, eb_bh,
+                                                         v_cluster,
+                                                         num_clusters);
+                        if (ret) {
+                                mlog_errno(ret);
+                                goto out;
+                        }
+                }
         } else {
                 rec = &el->l_recs[i];
 
@@ -162,7 +261,7 @@ out:
  * all while the map is in the process of being updated.
  */
 int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
-                                int *ret_count, unsigned int *extent_flags)
+                                u64 *ret_count, unsigned int *extent_flags)
 {
         int ret;
         int bpc = ocfs2_clusters_to_blocks(inode->i_sb, 1);