Btrfs: Integrate metadata reservation with start_transaction

Besides simplify the code, this change makes sure all metadata
reservation for normal metadata operations are released after
committing transaction.

Changes since V1:

Add code that check if unlink and rmdir will free space.

Add ENOSPC handling for clone ioctl.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 169 insertions, 114 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3367278ac6a1..657df6e002d3 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -616,6 +616,113 @@ int btrfs_lookup_extent(struct btrfs_root *root, u64 start, u64 len)
 }
 
 /*
+ * helper function to lookup reference count and flags of extent.
+ *
+ * the head node for delayed ref is used to store the sum of all the
+ * reference count modifications queued up in the rbtree. the head
+ * node may also store the extent flags to set. This way you can check
+ * to see what the reference count and extent flags would be if all of
+ * the delayed refs are not processed.
+ */
+int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
+                             struct btrfs_root *root, u64 bytenr,
+                             u64 num_bytes, u64 *refs, u64 *flags)
+{
+        struct btrfs_delayed_ref_head *head;
+        struct btrfs_delayed_ref_root *delayed_refs;
+        struct btrfs_path *path;
+        struct btrfs_extent_item *ei;
+        struct extent_buffer *leaf;
+        struct btrfs_key key;
+        u32 item_size;
+        u64 num_refs;
+        u64 extent_flags;
+        int ret;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = bytenr;
+        key.type = BTRFS_EXTENT_ITEM_KEY;
+        key.offset = num_bytes;
+        if (!trans) {
+                path->skip_locking = 1;
+                path->search_commit_root = 1;
+        }
+again:
+        ret = btrfs_search_slot(trans, root->fs_info->extent_root,
+                                &key, path, 0, 0);
+        if (ret < 0)
+                goto out_free;
+
+        if (ret == 0) {
+                leaf = path->nodes[0];
+                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+                if (item_size >= sizeof(*ei)) {
+                        ei = btrfs_item_ptr(leaf, path->slots[0],
+                                            struct btrfs_extent_item);
+                        num_refs = btrfs_extent_refs(leaf, ei);
+                        extent_flags = btrfs_extent_flags(leaf, ei);
+                } else {
+#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
+                        struct btrfs_extent_item_v0 *ei0;
+                        BUG_ON(item_size != sizeof(*ei0));
+                        ei0 = btrfs_item_ptr(leaf, path->slots[0],
+                                             struct btrfs_extent_item_v0);
+                        num_refs = btrfs_extent_refs_v0(leaf, ei0);
+                        /* FIXME: this isn't correct for data */
+                        extent_flags = BTRFS_BLOCK_FLAG_FULL_BACKREF;
+#else
+                        BUG();
+#endif
+                }
+                BUG_ON(num_refs == 0);
+        } else {
+                num_refs = 0;
+                extent_flags = 0;
+                ret = 0;
+        }
+
+        if (!trans)
+                goto out;
+
+        delayed_refs = &trans->transaction->delayed_refs;
+        spin_lock(&delayed_refs->lock);
+        head = btrfs_find_delayed_ref_head(trans, bytenr);
+        if (head) {
+                if (!mutex_trylock(&head->mutex)) {
+                        atomic_inc(&head->node.refs);
+                        spin_unlock(&delayed_refs->lock);
+
+                        btrfs_release_path(root->fs_info->extent_root, path);
+
+                        mutex_lock(&head->mutex);
+                        mutex_unlock(&head->mutex);
+                        btrfs_put_delayed_ref(&head->node);
+                        goto again;
+                }
+                if (head->extent_op && head->extent_op->update_flags)
+                        extent_flags |= head->extent_op->flags_to_set;
+                else
+                        BUG_ON(num_refs == 0);
+
+                num_refs += head->node.ref_mod;
+                mutex_unlock(&head->mutex);
+        }
+        spin_unlock(&delayed_refs->lock);
+out:
+        WARN_ON(num_refs == 0);
+        if (refs)
+                *refs = num_refs;
+        if (flags)
+                *flags = extent_flags;
+out_free:
+        btrfs_free_path(path);
+        return ret;
+}
+
+/*
  * Back reference rules.  Back refs have three main goals:
  *
  * 1) differentiate between all holders of references to an extent so that
@@ -2949,113 +3056,6 @@ again:
 }
 
 /*
- * unreserve num_items number of items worth of metadata space.  This needs to
- * be paired with btrfs_reserve_metadata_space.
- *
- * NOTE: if you have the option, run this _AFTER_ you do a
- * btrfs_end_transaction, since btrfs_end_transaction will run delayed ref
- * oprations which will result in more used metadata, so we want to make sure we
- * can do that without issue.
- */
-int btrfs_unreserve_metadata_space(struct btrfs_root *root, int num_items)
-{
-        struct btrfs_fs_info *info = root->fs_info;
-        struct btrfs_space_info *meta_sinfo;
-        u64 num_bytes;
-        u64 alloc_target;
-        bool bug = false;
-
-        /* get the space info for where the metadata will live */
-        alloc_target = btrfs_get_alloc_profile(root, 0);
-        meta_sinfo = __find_space_info(info, alloc_target);
-
-        num_bytes = calculate_bytes_needed(root, num_items);
-
-        spin_lock(&meta_sinfo->lock);
-        if (meta_sinfo->bytes_may_use < num_bytes) {
-                bug = true;
-                meta_sinfo->bytes_may_use = 0;
-        } else {
-                meta_sinfo->bytes_may_use -= num_bytes;
-        }
-        spin_unlock(&meta_sinfo->lock);
-
-        BUG_ON(bug);
-
-        return 0;
-}
-
-/*
- * Reserve some metadata space for use.  We'll calculate the worste case number
- * of bytes that would be needed to modify num_items number of items.  If we
- * have space, fantastic, if not, you get -ENOSPC.  Please call
- * btrfs_unreserve_metadata_space when you are done for the _SAME_ number of
- * items you reserved, since whatever metadata you needed should have already
- * been allocated.
- *
- * This will commit the transaction to make more space if we don't have enough
- * metadata space.  THe only time we don't do this is if we're reserving space
- * inside of a transaction, then we will just return -ENOSPC and it is the
- * callers responsibility to handle it properly.
- */
-int btrfs_reserve_metadata_space(struct btrfs_root *root, int num_items)
-{
-        struct btrfs_fs_info *info = root->fs_info;
-        struct btrfs_space_info *meta_sinfo;
-        u64 num_bytes;
-        u64 used;
-        u64 alloc_target;
-        int retries = 0;
-
-        /* get the space info for where the metadata will live */
-        alloc_target = btrfs_get_alloc_profile(root, 0);
-        meta_sinfo = __find_space_info(info, alloc_target);
-
-        num_bytes = calculate_bytes_needed(root, num_items);
-again:
-        spin_lock(&meta_sinfo->lock);
-
-        if (unlikely(!meta_sinfo->bytes_root))
-                meta_sinfo->bytes_root = calculate_bytes_needed(root, 6);
-
-        if (!retries)
-                meta_sinfo->bytes_may_use += num_bytes;
-
-        used = meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
-                meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly +
-                meta_sinfo->bytes_super + meta_sinfo->bytes_root +
-                meta_sinfo->bytes_may_use + meta_sinfo->bytes_delalloc;
-
-        if (used > meta_sinfo->total_bytes) {
-                retries++;
-                if (retries == 1) {
-                        if (maybe_allocate_chunk(NULL, root, meta_sinfo,
-                                                 num_bytes))
-                                goto again;
-                        retries++;
-                } else {
-                        spin_unlock(&meta_sinfo->lock);
-                }
-
-                if (retries == 2) {
-                        shrink_delalloc(NULL, root, meta_sinfo, num_bytes);
-                        goto again;
-                }
-                spin_lock(&meta_sinfo->lock);
-                meta_sinfo->bytes_may_use -= num_bytes;
-                spin_unlock(&meta_sinfo->lock);
-
-                dump_space_info(meta_sinfo, 0, 0);
-                return -ENOSPC;
-        }
-
-        check_force_delalloc(meta_sinfo);
-        spin_unlock(&meta_sinfo->lock);
-
-        return 0;
-}
-
-/*
  * This will check the space that the inode allocates from to make sure we have
  * enough space for bytes.
  */
@@ -3095,9 +3095,9 @@ again:
                         spin_unlock(&data_sinfo->lock);
 alloc:
                         alloc_target = btrfs_get_alloc_profile(root, 1);
-                        trans = btrfs_start_transaction(root, 1);
-                        if (!trans)
-                                return -ENOMEM;
+                        trans = btrfs_join_transaction(root, 1);
+                        if (IS_ERR(trans))
+                                return PTR_ERR(trans);
 
                         ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                              bytes + 2 * 1024 * 1024,
@@ -3118,8 +3118,8 @@ alloc:
                 if (!committed && !root->fs_info->open_ioctl_trans) {
                         committed = 1;
                         trans = btrfs_join_transaction(root, 1);
-                        if (!trans)
-                                return -ENOMEM;
+                        if (IS_ERR(trans))
+                                return PTR_ERR(trans);
                         ret = btrfs_commit_transaction(trans, root);
                         if (ret)
                                 return ret;
@@ -3701,6 +3701,59 @@ static void init_global_block_rsv(struct btrfs_fs_info *fs_info)
         fs_info->chunk_root->block_rsv = &fs_info->chunk_block_rsv;
 }
 
+static u64 calc_trans_metadata_size(struct btrfs_root *root, int num_items)
+{
+        return (root->leafsize + root->nodesize * (BTRFS_MAX_LEVEL - 1)) *
+                3 * num_items;
+}
+
+int btrfs_trans_reserve_metadata(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root,
+                                 int num_items, int *retries)
+{
+        u64 num_bytes;
+        int ret;
+
+        if (num_items == 0 || root->fs_info->chunk_root == root)
+                return 0;
+
+        num_bytes = calc_trans_metadata_size(root, num_items);
+        ret = btrfs_block_rsv_add(trans, root, &root->fs_info->trans_block_rsv,
+                                  num_bytes, retries);
+        if (!ret) {
+                trans->bytes_reserved += num_bytes;
+                trans->block_rsv = &root->fs_info->trans_block_rsv;
+        }
+        return ret;
+}
+
+void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
+                                  struct btrfs_root *root)
+{
+        if (!trans->bytes_reserved)
+                return;
+
+        BUG_ON(trans->block_rsv != &root->fs_info->trans_block_rsv);
+        btrfs_block_rsv_release(root, trans->block_rsv,
+                                trans->bytes_reserved);
+        trans->bytes_reserved = 0;
+}
+
+int btrfs_snap_reserve_metadata(struct btrfs_trans_handle *trans,
+                                struct btrfs_pending_snapshot *pending)
+{
+        struct btrfs_root *root = pending->root;
+        struct btrfs_block_rsv *src_rsv = get_block_rsv(trans, root);
+        struct btrfs_block_rsv *dst_rsv = &pending->block_rsv;
+        /*
+         * two for root back/forward refs, two for directory entries
+         * and one for root of the snapshot.
+         */
+        u64 num_bytes = calc_trans_metadata_size(root, 5);
+        dst_rsv->space_info = src_rsv->space_info;
+        return block_rsv_migrate_bytes(src_rsv, dst_rsv, num_bytes);
+}
+
 static int update_block_group(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               u64 bytenr, u64 num_bytes, int alloc)
@@ -5824,7 +5877,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref)
         wc = kzalloc(sizeof(*wc), GFP_NOFS);
         BUG_ON(!wc);
 
-        trans = btrfs_start_transaction(tree_root, 1);
+        trans = btrfs_start_transaction(tree_root, 0);
 
         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                 level = btrfs_header_level(root->node);
@@ -5920,7 +5973,9 @@ int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref)
                         BUG_ON(ret);
 
                         btrfs_end_transaction(trans, tree_root);
-                        trans = btrfs_start_transaction(tree_root, 1);
+                        trans = btrfs_start_transaction(tree_root, 0);
+                        if (IS_ERR(trans))
+                                return PTR_ERR(trans);
                 } else {
                         unsigned long update;
                         update = trans->delayed_ref_updates;