+/*
+ * For a given allocation, determine which allocators will need to be
+ * accessed, and lock them, reserving the appropriate number of bits.
+ *
+ * Called from ocfs2_extend_allocation() for file systems which don't
+ * support holes, and from ocfs2_prepare_write() for file systems
+ * which understand sparse inodes.
+ */
+static int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
+ u32 clusters_to_add,
+ struct ocfs2_alloc_context **data_ac,
+ struct ocfs2_alloc_context **meta_ac)
+{
+ int ret, num_free_extents;
+ struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+ *meta_ac = NULL;
+ *data_ac = NULL;
+
+ mlog(0, "extend inode %llu, i_size = %lld, di->i_clusters = %u, "
+ "clusters_to_add = %u\n",
+ (unsigned long long)OCFS2_I(inode)->ip_blkno, i_size_read(inode),
+ le32_to_cpu(di->i_clusters), clusters_to_add);
+
+ num_free_extents = ocfs2_num_free_extents(osb, inode, di);
+ if (num_free_extents < 0) {
+ ret = num_free_extents;
+ mlog_errno(ret);
+ goto out;
+ }
+
+ /*
+ * Sparse allocation file systems need to be more conservative
+ * with reserving room for expansion - the actual allocation
+ * happens while we've got a journal handle open so re-taking
+ * a cluster lock (because we ran out of room for another
+ * extent) will violate ordering rules.
+ *
+ * Most of the time we'll only be seeing this 1 page at a time
+ * anyway.
+ */
+ if (!num_free_extents ||
+ (ocfs2_sparse_alloc(osb) && num_free_extents < clusters_to_add)) {
+ ret = ocfs2_reserve_new_metadata(osb, di, meta_ac);
+ if (ret < 0) {
+ if (ret != -ENOSPC)
+ mlog_errno(ret);
+ goto out;
+ }
+ }
+
+ ret = ocfs2_reserve_clusters(osb, clusters_to_add, data_ac);
+ if (ret < 0) {
+ if (ret != -ENOSPC)
+ mlog_errno(ret);
+ goto out;
+ }
+
+out:
+ if (ret) {
+ if (*meta_ac) {
+ ocfs2_free_alloc_context(*meta_ac);
+ *meta_ac = NULL;
+ }
+
+ /*
+ * We cannot have an error and a non null *data_ac.
+ */
+ }
+
+ return ret;
+}
+