From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51558) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YJOpD-0007U2-8e for qemu-devel@nongnu.org; Thu, 05 Feb 2015 10:58:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YJOp9-0008BB-74 for qemu-devel@nongnu.org; Thu, 05 Feb 2015 10:58:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56395) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YJOp9-0008B7-07 for qemu-devel@nongnu.org; Thu, 05 Feb 2015 10:58:35 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t15FwYx4029290 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 5 Feb 2015 10:58:34 -0500 From: Max Reitz Date: Thu, 5 Feb 2015 10:58:32 -0500 Message-Id: <1423151912-24863-1-git-send-email-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH v2] qcow2: Rewrite qcow2_alloc_bytes() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi , Max Reitz qcow2_alloc_bytes() is a function with insufficient error handling and an unnecessary goto. This patch rewrites it. Signed-off-by: Max Reitz --- v2: - s/free_cluster_index/free_byte_index/ [Eric] - added an assertion at the start of the function that s->free_byte_offset is either 0 or points to the tail of a cluster (but never to the start) - use ROUND_UP() instead of start_of_cluster() + cluster_size [Eric] - added an assertion that s->free_byte_offset is set before using it [Eric] --- block/qcow2-refcount.c | 77 +++++++++++++++++++++++++++++--------------------- 1 file changed, 45 insertions(+), 32 deletions(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 9afdb40..eede60d 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -759,46 +759,51 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) { BDRVQcowState *s = bs->opaque; - int64_t offset, cluster_offset; - int free_in_cluster; + int64_t offset, new_cluster = 0, cluster_end; + size_t free_in_cluster; BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES); assert(size > 0 && size <= s->cluster_size); - if (s->free_byte_offset == 0) { - offset = qcow2_alloc_clusters(bs, s->cluster_size); - if (offset < 0) { - return offset; + assert(!s->free_byte_offset || offset_into_cluster(s, s->free_byte_offset)); + + if (s->free_byte_offset) { + int refcount = qcow2_get_refcount(bs, + s->free_byte_offset >> s->cluster_bits); + if (refcount < 0) { + return refcount; + } + + if (refcount == 0xffff) { + s->free_byte_offset = 0; } - s->free_byte_offset = offset; } - redo: + free_in_cluster = s->cluster_size - offset_into_cluster(s, s->free_byte_offset); - if (size <= free_in_cluster) { - /* enough space in current cluster */ - offset = s->free_byte_offset; - s->free_byte_offset += size; - free_in_cluster -= size; - if (free_in_cluster == 0) - s->free_byte_offset = 0; - if (offset_into_cluster(s, offset) != 0) - qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, - QCOW2_DISCARD_NEVER); - } else { - offset = qcow2_alloc_clusters(bs, s->cluster_size); - if (offset < 0) { - return offset; + + if (!s->free_byte_offset || free_in_cluster < size) { + new_cluster = qcow2_alloc_clusters(bs, s->cluster_size); + if (new_cluster < 0) { + return new_cluster; + } + + cluster_end = ROUND_UP(s->free_byte_offset, s->cluster_size); + if (!s->free_byte_offset || cluster_end != new_cluster) { + s->free_byte_offset = new_cluster; } - cluster_offset = start_of_cluster(s, s->free_byte_offset); - if ((cluster_offset + s->cluster_size) == offset) { - /* we are lucky: contiguous data */ - offset = s->free_byte_offset; - qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, - QCOW2_DISCARD_NEVER); - s->free_byte_offset += size; - } else { - s->free_byte_offset = offset; - goto redo; + } + + assert(s->free_byte_offset); + if (offset_into_cluster(s, s->free_byte_offset)) { + int ret = qcow2_update_cluster_refcount(bs, + s->free_byte_offset >> s->cluster_bits, 1, + QCOW2_DISCARD_NEVER); + if (ret < 0) { + if (new_cluster > 0) { + qcow2_free_clusters(bs, new_cluster, s->cluster_size, + QCOW2_DISCARD_OTHER); + } + return ret; } } @@ -807,6 +812,14 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) * be flushed before the caller's L2 table updates. */ qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); + + offset = s->free_byte_offset; + + s->free_byte_offset += size; + if (!offset_into_cluster(s, s->free_byte_offset)) { + s->free_byte_offset = 0; + } + return offset; } -- 2.1.0