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[Qemu-block] [PATCH v2] qcow2: do not allocate extra memory
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[Qemu-block] [PATCH v2] qcow2: do not allocate extra memory |
Date: |
Thu, 14 Jul 2016 19:59:25 +0300 |
There are no needs to allocate more than one cluster, as we set
avail_out for deflate to one cluster.
Zlib docs (http://www.zlib.net/manual.html) says:
"deflate compresses as much data as possible, and stops when the input
buffer becomes empty or the output buffer becomes full."
So, deflate will not write more than avail_out to output buffer. If
there is no enough space in output buffer for compressed data (it may be
larger than input data) deflate just returns Z_OK. (if all data is
compressed and written to output buffer deflate returns Z_STREAM_END).
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
v2: improve commit message
block/qcow.c | 2 +-
block/qcow2.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/block/qcow.c b/block/qcow.c
index ac849bd..d8826f3 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -983,7 +983,7 @@ static int qcow_write_compressed(BlockDriverState *bs,
int64_t sector_num,
return ret;
}
- out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
+ out_buf = g_malloc(s->cluster_size);
/* best compression, small window, no zlib header */
memset(&strm, 0, sizeof(strm));
diff --git a/block/qcow2.c b/block/qcow2.c
index a5ea19b..b1c90ae 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2612,7 +2612,7 @@ static int qcow2_write_compressed(BlockDriverState *bs,
int64_t sector_num,
return ret;
}
- out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
+ out_buf = g_malloc(s->cluster_size);
/* best compression, small window, no zlib header */
memset(&strm, 0, sizeof(strm));
--
1.8.3.1
- [Qemu-block] [PATCH v2] qcow2: do not allocate extra memory,
Vladimir Sementsov-Ogievskiy <=