From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NWqTP-0006l8-Jn for qemu-devel@nongnu.org; Mon, 18 Jan 2010 07:12:47 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NWqTK-0006hd-3t for qemu-devel@nongnu.org; Mon, 18 Jan 2010 07:12:46 -0500 Received: from [199.232.76.173] (port=51041 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NWqTJ-0006hY-Ka for qemu-devel@nongnu.org; Mon, 18 Jan 2010 07:12:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6801) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NWqTJ-0001bq-9T for qemu-devel@nongnu.org; Mon, 18 Jan 2010 07:12:41 -0500 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o0ICCeih029110 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 18 Jan 2010 07:12:40 -0500 From: Kevin Wolf Date: Mon, 18 Jan 2010 13:11:33 +0100 Message-Id: <1263816696-24122-8-git-send-email-kwolf@redhat.com> In-Reply-To: <1263816696-24122-1-git-send-email-kwolf@redhat.com> References: <1263816696-24122-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 07/10] qcow2: Improve error handling in update_refcount List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf If update_refcount fails, try to undo any changes made so far to avoid inconsistencies in the image file. Signed-off-by: Kevin Wolf --- block/qcow2-refcount.c | 32 +++++++++++++++++++++++++------- 1 files changed, 25 insertions(+), 7 deletions(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 6f449c6..a84620f 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -278,6 +278,7 @@ static int update_refcount(BlockDriverState *bs, int64_t refcount_block_offset = 0; int64_t table_index = -1, old_table_index; int first_index = -1, last_index = -1; + int ret; #ifdef DEBUG_ALLOC2 printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n", @@ -292,6 +293,7 @@ static int update_refcount(BlockDriverState *bs, { int block_index, refcount; int64_t cluster_index = cluster_offset >> s->cluster_bits; + int64_t new_block; /* Only write refcount block to disk when we are done with it */ old_table_index = table_index; @@ -309,10 +311,12 @@ static int update_refcount(BlockDriverState *bs, } /* Load the refcount block and allocate it if needed */ - refcount_block_offset = alloc_refcount_block(bs, cluster_index); - if (refcount_block_offset < 0) { - return refcount_block_offset; + new_block = alloc_refcount_block(bs, cluster_index); + if (new_block < 0) { + ret = new_block; + goto fail; } + refcount_block_offset = new_block; /* we can update the count and save it */ block_index = cluster_index & @@ -326,24 +330,38 @@ static int update_refcount(BlockDriverState *bs, refcount = be16_to_cpu(s->refcount_block_cache[block_index]); refcount += addend; - if (refcount < 0 || refcount > 0xffff) - return -EINVAL; + if (refcount < 0 || refcount > 0xffff) { + ret = -EINVAL; + goto fail; + } if (refcount == 0 && cluster_index < s->free_cluster_index) { s->free_cluster_index = cluster_index; } s->refcount_block_cache[block_index] = cpu_to_be16(refcount); } + ret = 0; +fail: + /* Write last changed block to disk */ if (refcount_block_offset != 0) { if (write_refcount_block_entries(s, refcount_block_offset, first_index, last_index) < 0) { - return -EIO; + return ret < 0 ? ret : -EIO; } } - return 0; + /* + * Try do undo any updates if an error is returned (This may succeed in + * some cases like ENOSPC for allocating a new refcount block) + */ + if (ret < 0) { + int dummy; + dummy = update_refcount(bs, offset, cluster_offset - offset, -addend); + } + + return ret; } /* addend must be 1 or -1 */ -- 1.6.2.5