Ocfs2/move_extents: helper to validate and adjust moving goal.

First best-effort attempt to validate and adjust the goal (physical address in
block), while it can't guarantee later operation can succeed all the time since
global_bitmap may change a bit over time.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>

diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
index 68e00b4..e928a88 100644 (file)
--- a/fs/ocfs2/move_extents.c
+++ b/fs/ocfs2/move_extents.c
@@ -455,3 +455,64 @@ out:
         */
        return ret;
 }
+
+/*
+ * XXX: helper to validate and adjust moving goal.
+ */
+static int ocfs2_validate_and_adjust_move_goal(struct inode *inode,
+                                              struct ocfs2_move_extents *range)
+{
+       int ret, goal_bit = 0;
+
+       struct buffer_head *gd_bh = NULL;
+       struct ocfs2_group_desc *bg;
+       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+       int c_to_b = 1 << (osb->s_clustersize_bits -
+                                       inode->i_sb->s_blocksize_bits);
+
+       /*
+        * validate goal sits within global_bitmap, and return the victim
+        * group desc
+        */
+       ret = ocfs2_find_victim_alloc_group(inode, range->me_goal,
+                                           GLOBAL_BITMAP_SYSTEM_INODE,
+                                           OCFS2_INVALID_SLOT,
+                                           &goal_bit, &gd_bh);
+       if (ret)
+               goto out;
+
+       bg = (struct ocfs2_group_desc *)gd_bh->b_data;
+
+       /*
+        * make goal become cluster aligned.
+        */
+       if (range->me_goal % c_to_b)
+               range->me_goal = range->me_goal / c_to_b * c_to_b;
+
+       /*
+        * moving goal is not allowd to start with a group desc blok(#0 blk)
+        * let's compromise to the latter cluster.
+        */
+       if (range->me_goal == le64_to_cpu(bg->bg_blkno))
+               range->me_goal += c_to_b;
+
+       /*
+        * movement is not gonna cross two groups.
+        */
+       if ((le16_to_cpu(bg->bg_bits) - goal_bit) * osb->s_clustersize <
+                                                               range->me_len) {
+               ret = -EINVAL;
+               goto out;
+       }
+       /*
+        * more exact validations/adjustments will be performed later during
+        * moving operation for each extent range.
+        */
+       mlog(0, "extents get ready to be moved to #%llu block\n",
+            range->me_goal);
+
+out:
+       brelse(gd_bh);
+
+       return ret;
+}