From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50510) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSmbz-0001wS-Po for qemu-devel@nongnu.org; Wed, 26 Mar 2014 08:07:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WSmbt-0004AC-RE for qemu-devel@nongnu.org; Wed, 26 Mar 2014 08:07:15 -0400 From: Stefan Hajnoczi Date: Wed, 26 Mar 2014 13:05:56 +0100 Message-Id: <1395835569-21193-35-git-send-email-stefanha@redhat.com> In-Reply-To: <1395835569-21193-1-git-send-email-stefanha@redhat.com> References: <1395835569-21193-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH for-2.0 34/47] dmg: drop broken bdrv_pread() loop List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , pmatouse@redhat.com, qemu-stable@nongnu.org, Stefan Hajnoczi It is not necessary to check errno for EINTR and the block layer does not produce short reads. Therefore we can drop the loop that attempts to read a compressed chunk. The loop is buggy because it incorrectly adds the transferred bytes twice: do { ret = bdrv_pread(...); i += ret; } while (ret >= 0 && ret + i < s->lengths[chunk]); Luckily we can drop the loop completely and perform a single bdrv_pread(). Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/dmg.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/block/dmg.c b/block/dmg.c index f4f3e8e..1cc5426 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -298,21 +298,10 @@ static inline int dmg_read_chunk(BlockDriverState *bs, int sector_num) s->current_chunk = s->n_chunks; switch (s->types[chunk]) { case 0x80000005: { /* zlib compressed */ - int i; - /* we need to buffer, because only the chunk as whole can be * inflated. */ - i = 0; - do { - ret = bdrv_pread(bs->file, s->offsets[chunk] + i, - s->compressed_chunk + i, - s->lengths[chunk] - i); - if (ret < 0 && errno == EINTR) { - ret = 0; - } - i += ret; - } while (ret >= 0 && ret + i < s->lengths[chunk]); - + ret = bdrv_pread(bs->file, s->offsets[chunk], + s->compressed_chunk, s->lengths[chunk]); if (ret != s->lengths[chunk]) { return -1; } -- 1.8.5.3