Ocfs2/move_extents: helper to probe a proper region to move in an alloc group.

Before doing the movement of extents, we'd better probe the alloc group from
'goal_blk' for searching a contiguous region to fit the wanted movement, we
even will have a best-effort try by compromising to a threshold around the
given goal.

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

1 files changed, 39 insertions, 0 deletions

diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
index e928a88f2db1..ebaff625fc28 100644
--- a/fs/ocfs2/move_extents.c
+++ b/fs/ocfs2/move_extents.c
@@ -516,3 +516,42 @@ out:
 
         return ret;
 }
+
+static void ocfs2_probe_alloc_group(struct inode *inode, struct buffer_head *bh,
+                                    int *goal_bit, u32 move_len, u32 max_hop,
+                                    u32 *phys_cpos)
+{
+        int i, used, last_free_bits = 0, base_bit = *goal_bit;
+        struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;
+        u32 base_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
+                                                 le64_to_cpu(gd->bg_blkno));
+
+        for (i = base_bit; i < le16_to_cpu(gd->bg_bits); i++) {
+
+                used = ocfs2_test_bit(i, (unsigned long *)gd->bg_bitmap);
+                if (used) {
+                        /*
+                         * we even tried searching the free chunk by jumping
+                         * a 'max_hop' distance, but still failed.
+                         */
+                        if ((i - base_bit) > max_hop) {
+                                *phys_cpos = 0;
+                                break;
+                        }
+
+                        if (last_free_bits)
+                                last_free_bits = 0;
+
+                        continue;
+                } else
+                        last_free_bits++;
+
+                if (last_free_bits == move_len) {
+                        *goal_bit = i;
+                        *phys_cpos = base_cpos + i;
+                        break;
+                }
+        }
+
+        mlog(0, "found phys_cpos: %u to fit the wanted moving.\n", *phys_cpos);
+}