Btrfs: Properly handle overlapping extent in shrink_extent_tree

The patch fixes the overlapping extent issue in shrink_extent_tree.
It checks whether there is an overlapping extent by using
find_previous_extent. If there is an overlapping extent, it setups
key.objectid and cur_byte properly.

---

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 56 insertions, 84 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cc89df4493ab..426a0222e12f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2317,36 +2317,6 @@ out:
         return ret;
 }
 
-static int find_overlapping_extent(struct btrfs_root *root,
-                                   struct btrfs_path *path, u64 new_size)
-{
-        struct btrfs_key found_key;
-        struct extent_buffer *leaf;
-        int ret;
-
-        while(1) {
-                if (path->slots[0] == 0) {
-                        ret = btrfs_prev_leaf(root, path);
-                        if (ret == 1) {
-                                return 1;
-                        }
-                        if (ret < 0)
-                                return ret;
-                } else {
-                        path->slots[0]--;
-                }
-                leaf = path->nodes[0];
-                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-                if (found_key.type == BTRFS_EXTENT_ITEM_KEY) {
-                        if (found_key.objectid + found_key.offset > new_size)
-                                return 0;
-                        else
-                                return 1;
-                }
-        }
-        return 1;
-}
-
 int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
 {
         struct btrfs_trans_handle *trans;
@@ -2357,11 +2327,10 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
         struct btrfs_fs_info *info = root->fs_info;
         struct extent_map_tree *block_group_cache;
         struct btrfs_key key;
-        struct btrfs_key found_key = { 0, 0, 0 };
+        struct btrfs_key found_key;
         struct extent_buffer *leaf;
         u32 nritems;
         int ret;
-        int slot;
 
         btrfs_set_super_total_bytes(&info->super_copy, new_size);
         block_group_cache = &info->block_group_cache;
@@ -2372,48 +2341,54 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
 again:
         total_found = 0;
         key.objectid = new_size;
-        cur_byte = key.objectid;
         key.offset = 0;
         key.type = 0;
-        while(1) {
+        cur_byte = key.objectid;
 
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (ret < 0)
+                goto out;
+
+        ret = find_previous_extent(root, path);
+        if (ret < 0)
+                goto out;
+        if (ret == 0) {
+                leaf = path->nodes[0];
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (found_key.objectid + found_key.offset > new_size) {
+                        cur_byte = found_key.objectid;
+                        key.objectid = cur_byte;
+                }
+        }
+        btrfs_release_path(root, path);
+
+        while(1) {
                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                 if (ret < 0)
                         goto out;
-next:
+
                 leaf = path->nodes[0];
-                if (key.objectid == new_size - 1) {
-                        ret = find_overlapping_extent(root, path, new_size);
-                        if (ret != 0) {
-                                btrfs_release_path(root, path);
-                                ret = btrfs_search_slot(NULL, root, &key,
-                                                        path, 0, 0);
-                                if (ret < 0)
-                                        goto out;
+                nritems = btrfs_header_nritems(leaf);
+next:
+                if (path->slots[0] >= nritems) {
+                        ret = btrfs_next_leaf(root, path);
+                        if (ret < 0)
+                                goto out;
+                        if (ret == 1) {
+                                ret = 0;
+                                break;
                         }
+                        leaf = path->nodes[0];
+                        nritems = btrfs_header_nritems(leaf);
                 }
-                nritems = btrfs_header_nritems(leaf);
-                ret = 0;
-                slot = path->slots[0];
-                if (slot < nritems)
-                        btrfs_item_key_to_cpu(leaf, &found_key, slot);
-                if (slot == nritems ||
-                    btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY) {
+
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
+                    found_key.objectid + found_key.offset <= cur_byte) {
                         path->slots[0]++;
-                        if (path->slots[0] >= nritems) {
-                                ret = btrfs_next_leaf(root, path);
-                                if (ret < 0)
-                                        goto out;
-                                if (ret == 1) {
-                                        ret = 0;
-                                        break;
-                                }
-                        }
                         goto next;
                 }
-                btrfs_item_key_to_cpu(leaf, &found_key, slot);
-                if (found_key.objectid + found_key.offset <= cur_byte)
-                        continue;
+
                 total_found++;
                 cur_byte = found_key.objectid + found_key.offset;
                 key.objectid = cur_byte;
@@ -2446,33 +2421,30 @@ next:
                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                 if (ret < 0)
                         goto out;
-bg_next:
+
                 leaf = path->nodes[0];
                 nritems = btrfs_header_nritems(leaf);
-                ret = 0;
-                slot = path->slots[0];
-                if (slot < nritems)
-                        btrfs_item_key_to_cpu(leaf, &found_key, slot);
-                if (slot == nritems ||
-                    btrfs_key_type(&found_key) != BTRFS_BLOCK_GROUP_ITEM_KEY) {
-                        if (slot < nritems) {
-                                printk("shrinker found key %Lu %u %Lu\n",
-                                       found_key.objectid, found_key.type,
-                                       found_key.offset);
-                                path->slots[0]++;
-                        }
-                        if (path->slots[0] >= nritems) {
-                                ret = btrfs_next_leaf(root, path);
-                                if (ret < 0)
-                                        break;
-                                if (ret == 1) {
-                                        ret = 0;
-                                        break;
-                                }
+bg_next:
+                if (path->slots[0] >= nritems) {
+                        ret = btrfs_next_leaf(root, path);
+                        if (ret < 0)
+                                break;
+                        if (ret == 1) {
+                                ret = 0;
+                                break;
                         }
+                        leaf = path->nodes[0];
+                        nritems = btrfs_header_nritems(leaf);
+                }
+
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (btrfs_key_type(&found_key) != BTRFS_BLOCK_GROUP_ITEM_KEY) {
+                        printk("shrinker found key %Lu %u %Lu\n",
+                                found_key.objectid, found_key.type,
+                                found_key.offset);
+                        path->slots[0]++;
                         goto bg_next;
                 }
-                btrfs_item_key_to_cpu(leaf, &found_key, slot);
                 ret = get_state_private(&info->block_group_cache,
                                         found_key.objectid, &ptr);
                 if (!ret)