From 35538bdb46122fdf90ca869df29869b8aeaefa09 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 25 Mar 2014 14:23:42 +0100 Subject: [PATCH 35/49] dmg: drop broken bdrv_pread() loop RH-Author: Kevin Wolf Message-id: <1395753835-7591-36-git-send-email-kwolf@redhat.com> Patchwork-id: n/a O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 35/48] dmg: drop broken bdrv_pread() loop Bugzilla: 1066691 RH-Acked-by: Jeff Cody RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Paolo Bonzini From: Stefan Hajnoczi Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1066691 Upstream status: Series embargoed 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 files 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; } -- 1.7.1