ocfs2: Add empty bucket support in xattr.

As Mark mentioned, it may be time-consuming when we remove the
empty xattr bucket, so this patch try to let empty bucket exist
in xattr operation. The modification includes:
1. Remove the functin of bucket and extent record deletion during
   xattr delete.
2. In xattr set:
   1) Don't clean the last entry so that if the bucket is empty,
      the hash value of the bucket is the hash value of the entry
      which is deleted last.
   2) During insert, if we meet with an empty bucket, just use the
      1st entry.
3. In binary search of xattr bucket, use the bucket hash value(which
   stored in the 1st xattr entry) to find the right place.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/xattr.c

@@ -2301,9 +2301,12 @@ static int ocfs2_xattr_bucket_find(struct inode *inode,
 
 		/*
 		 * Check whether the hash of the last entry in our
-		 * bucket is larger than the search one.
+		 * bucket is larger than the search one. for an empty
+		 * bucket, the last one is also the first one.
 		 */
-		xe = &xh->xh_entries[le16_to_cpu(xh->xh_count) - 1];
+		if (xh->xh_count)
+			xe = &xh->xh_entries[le16_to_cpu(xh->xh_count) - 1];
+
 		last_hash = le32_to_cpu(xe->xe_name_hash);
 
 		/* record lower_bh which may be the insert place. */
@@ -2450,7 +2453,8 @@ static int ocfs2_iterate_xattr_buckets(struct inode *inode,
 		if (i == 0)
 			num_buckets = le16_to_cpu(bucket.xh->xh_num_buckets);
 
-		mlog(0, "iterating xattr bucket %llu\n", blkno);
+		mlog(0, "iterating xattr bucket %llu, first hash %u\n", blkno,
+		     le32_to_cpu(bucket.xh->xh_entries[0].xe_name_hash));
 		if (func) {
 			ret = func(inode, &bucket, para);
 			if (ret) {
@@ -3915,8 +3919,6 @@ static inline char *ocfs2_xattr_bucket_get_val(struct inode *inode,
 
 /*
  * Handle the normal xattr set, including replace, delete and new.
- * When the bucket is empty, "is_empty" is set and the caller can
- * free this bucket.
  *
  * Note: "local" indicates the real data's locality. So we can't
  * just its bucket locality by its length.
@@ -3925,8 +3927,7 @@ static void ocfs2_xattr_set_entry_normal(struct inode *inode,
 					 struct ocfs2_xattr_info *xi,
 					 struct ocfs2_xattr_search *xs,
 					 u32 name_hash,
-					 int local,
-					 int *is_empty)
+					 int local)
 {
 	struct ocfs2_xattr_entry *last, *xe;
 	int name_len = strlen(xi->name);
@@ -3979,14 +3980,23 @@ static void ocfs2_xattr_set_entry_normal(struct inode *inode,
 			ocfs2_xattr_set_local(xe, local);
 			return;
 		} else {
-			/* Remove the old entry. */
+			/*
+			 * Remove the old entry if there is more than one.
+			 * We don't remove the last entry so that we can
+			 * use it to indicate the hash value of the empty
+			 * bucket.
+			 */
 			last -= 1;
-			memmove(xe, xe + 1,
-				(void *)last - (void *)xe);
-			memset(last, 0, sizeof(struct ocfs2_xattr_entry));
 			le16_add_cpu(&xh->xh_count, -1);
-			if (xh->xh_count == 0 && is_empty)
-				*is_empty = 1;
+			if (xh->xh_count) {
+				memmove(xe, xe + 1,
+					(void *)last - (void *)xe);
+				memset(last, 0,
+				       sizeof(struct ocfs2_xattr_entry));
+			} else
+				xh->xh_free_start =
+					cpu_to_le16(OCFS2_XATTR_BUCKET_SIZE);
+
 			return;
 		}
 	} else {
@@ -3994,7 +4004,7 @@ static void ocfs2_xattr_set_entry_normal(struct inode *inode,
 		int low = 0, high = count - 1, tmp;
 		struct ocfs2_xattr_entry *tmp_xe;
 
-		while (low <= high) {
+		while (low <= high && count) {
 			tmp = (low + high) / 2;
 			tmp_xe = &xh->xh_entries[tmp];
 
@@ -4090,8 +4100,7 @@ static int ocfs2_xattr_set_entry_in_bucket(struct inode *inode,
 					   struct ocfs2_xattr_info *xi,
 					   struct ocfs2_xattr_search *xs,
 					   u32 name_hash,
-					   int local,
-					   int *bucket_empty)
+					   int local)
 {
 	int i, ret;
 	handle_t *handle = NULL;
@@ -4130,8 +4139,7 @@ static int ocfs2_xattr_set_entry_in_bucket(struct inode *inode,
 		}
 	}
 
-	ocfs2_xattr_set_entry_normal(inode, xi, xs, name_hash,
-				     local, bucket_empty);
+	ocfs2_xattr_set_entry_normal(inode, xi, xs, name_hash, local);
 
 	/*Only dirty the blocks we have touched in set xattr. */
 	ret = ocfs2_xattr_bucket_handle_journal(inode, handle, xs,
@@ -4280,69 +4288,6 @@ static int ocfs2_xattr_bucket_set_value_outside(struct inode *inode,
 	return __ocfs2_xattr_set_value_outside(inode, xv, val, value_len);
 }
 
-/*
- * Remove the xattr bucket pointed by bucket_bh.
- * All the buckets after it in the same xattr extent rec will be
- * move forward one by one.
- */
-static int ocfs2_rm_xattr_bucket(struct inode *inode,
-				 struct buffer_head *first_bh,
-				 struct ocfs2_xattr_bucket *bucket)
-{
-	int ret = 0, credits;
-	struct ocfs2_xattr_header *xh =
-				(struct ocfs2_xattr_header *)first_bh->b_data;
-	u16 bucket_num = le16_to_cpu(xh->xh_num_buckets);
-	u64 end, start = bucket->bhs[0]->b_blocknr;
-	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
-	handle_t *handle;
-	u16 blk_per_bucket = ocfs2_blocks_per_xattr_bucket(inode->i_sb);
-
-	end = first_bh->b_blocknr + (bucket_num - 1) * blk_per_bucket;
-
-	mlog(0, "rm xattr bucket %llu\n", start);
-	/*
-	 * We need to update the first xattr_header and all the buckets starting
-	 * from start in this xattr rec.
-	 *
-	 * XXX: Should we empty the old last bucket here?
-	 */
-	credits = 1 + end - start;
-	handle = ocfs2_start_trans(osb, credits);
-	if (IS_ERR(handle)) {
-		ret = PTR_ERR(handle);
-		mlog_errno(ret);
-		return ret;
-	}
-
-	ret = ocfs2_journal_access(handle, inode, first_bh,
-				   OCFS2_JOURNAL_ACCESS_WRITE);
-	if (ret) {
-		mlog_errno(ret);
-		goto out_commit;
-	}
-
-
-	while (start < end) {
-		ret = ocfs2_cp_xattr_bucket(inode, handle,
-					    start + blk_per_bucket,
-					    start, 0);
-		if (ret) {
-			mlog_errno(ret);
-			goto out_commit;
-		}
-		start += blk_per_bucket;
-	}
-
-	/* update the first_bh. */
-	xh->xh_num_buckets = cpu_to_le16(bucket_num - 1);
-	ocfs2_journal_dirty(handle, first_bh);
-
-out_commit:
-	ocfs2_commit_trans(osb, handle);
-	return ret;
-}
-
 static int ocfs2_rm_xattr_cluster(struct inode *inode,
 				  struct buffer_head *root_bh,
 				  u64 blkno,
@@ -4432,57 +4377,6 @@ out:
 	return ret;
 }
 
-/*
- * Free the xattr bucket indicated by xs->bucket and if all the buckets
- * in the clusters is free, free the clusters also.
- */
-static int ocfs2_xattr_bucket_shrink(struct inode *inode,
-				     struct ocfs2_xattr_info *xi,
-				     struct ocfs2_xattr_search *xs,
-				     u32 name_hash)
-{
-	int ret;
-	u32 e_cpos, num_clusters;
-	u64 p_blkno;
-	struct buffer_head *first_bh = NULL;
-	struct ocfs2_xattr_header *first_xh;
-	struct ocfs2_xattr_block *xb =
-			(struct ocfs2_xattr_block *)xs->xattr_bh->b_data;
-
-	BUG_ON(xs->header->xh_count != 0);
-
-	ret = ocfs2_xattr_get_rec(inode, name_hash, &p_blkno,
-				  &e_cpos, &num_clusters,
-				  &xb->xb_attrs.xb_root.xt_list);
-	if (ret) {
-		mlog_errno(ret);
-		return ret;
-	}
-
-	ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), p_blkno,
-			       &first_bh, OCFS2_BH_CACHED, inode);
-	if (ret) {
-		mlog_errno(ret);
-		return ret;
-	}
-
-	ret = ocfs2_rm_xattr_bucket(inode, first_bh, &xs->bucket);
-	if (ret) {
-		mlog_errno(ret);
-		goto out;
-	}
-
-	first_xh = (struct ocfs2_xattr_header *)first_bh->b_data;
-	if (first_xh->xh_num_buckets == 0)
-		ret = ocfs2_rm_xattr_cluster(inode, xs->xattr_bh,
-					     p_blkno, e_cpos,
-					     num_clusters);
-
-out:
-	brelse(first_bh);
-	return ret;
-}
-
 static void ocfs2_xattr_bucket_remove_xs(struct inode *inode,
 					 struct ocfs2_xattr_search *xs)
 {
@@ -4534,7 +4428,7 @@ static int ocfs2_xattr_set_in_bucket(struct inode *inode,
 				     struct ocfs2_xattr_info *xi,
 				     struct ocfs2_xattr_search *xs)
 {
-	int ret, local = 1, bucket_empty = 0;
+	int ret, local = 1;
 	size_t value_len;
 	char *val = (char *)xi->value;
 	struct ocfs2_xattr_entry *xe = xs->here;
@@ -4580,34 +4474,29 @@ static int ocfs2_xattr_set_in_bucket(struct inode *inode,
 		xi->value_len = OCFS2_XATTR_ROOT_SIZE;
 	}
 
-	ret = ocfs2_xattr_set_entry_in_bucket(inode, xi, xs, name_hash,
-					      local, &bucket_empty);
+	ret = ocfs2_xattr_set_entry_in_bucket(inode, xi, xs, name_hash, local);
 	if (ret) {
 		mlog_errno(ret);
 		goto out;
 	}
 
-	if (value_len > OCFS2_XATTR_INLINE_SIZE) {
-		/* allocate the space now for the outside block storage. */
-		ret = ocfs2_xattr_bucket_value_truncate_xs(inode, xs,
-							   value_len);
-		if (ret) {
-			mlog_errno(ret);
+	if (value_len <= OCFS2_XATTR_INLINE_SIZE)
+		goto out;
 
-			if (xs->not_found) {
-				/*
-				 * We can't allocate enough clusters for outside
-				 * storage and we have allocated xattr already,
-				 * so need to remove it.
-				 */
-				ocfs2_xattr_bucket_remove_xs(inode, xs);
-			}
-			goto out;
+	/* allocate the space now for the outside block storage. */
+	ret = ocfs2_xattr_bucket_value_truncate_xs(inode, xs,
+						   value_len);
+	if (ret) {
+		mlog_errno(ret);
+
+		if (xs->not_found) {
+			/*
+			 * We can't allocate enough clusters for outside
+			 * storage and we have allocated xattr already,
+			 * so need to remove it.
+			 */
+			ocfs2_xattr_bucket_remove_xs(inode, xs);
 		}
-	} else {
-		if (bucket_empty)
-			ret = ocfs2_xattr_bucket_shrink(inode, xi,
-							xs, name_hash);
 		goto out;
 	}