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[Qemu-devel] [PATCH v2 2/4] block/null-{co, aio}: Allow reading zeroes
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH v2 2/4] block/null-{co, aio}: Allow reading zeroes |
Date: |
Thu, 24 Mar 2016 23:33:58 +0100 |
This is optional so that it does not impede the null block driver's
performance unless this behavior is desired.
Signed-off-by: Max Reitz <address@hidden>
---
block/null.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/block/null.c b/block/null.c
index d90165d..a7df386 100644
--- a/block/null.c
+++ b/block/null.c
@@ -14,10 +14,12 @@
#include "block/block_int.h"
#define NULL_OPT_LATENCY "latency-ns"
+#define NULL_OPT_ZEROES "read-zeroes"
typedef struct {
int64_t length;
int64_t latency_ns;
+ bool read_zeroes;
} BDRVNullState;
static QemuOptsList runtime_opts = {
@@ -40,6 +42,11 @@ static QemuOptsList runtime_opts = {
.help = "nanoseconds (approximated) to wait "
"before completing request",
},
+ {
+ .name = NULL_OPT_ZEROES,
+ .type = QEMU_OPT_BOOL,
+ .help = "return zeroes when read",
+ },
{ /* end of list */ }
},
};
@@ -61,6 +68,7 @@ static int null_file_open(BlockDriverState *bs, QDict
*options, int flags,
error_setg(errp, "latency-ns is invalid");
ret = -EINVAL;
}
+ s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false);
qemu_opts_del(opts);
return ret;
}
@@ -90,6 +98,12 @@ static coroutine_fn int null_co_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
QEMUIOVector *qiov)
{
+ BDRVNullState *s = bs->opaque;
+
+ if (s->read_zeroes) {
+ qemu_iovec_memset(qiov, 0, 0, nb_sectors * BDRV_SECTOR_SIZE);
+ }
+
return null_co_common(bs);
}
@@ -159,6 +173,12 @@ static BlockAIOCB *null_aio_readv(BlockDriverState *bs,
BlockCompletionFunc *cb,
void *opaque)
{
+ BDRVNullState *s = bs->opaque;
+
+ if (s->read_zeroes) {
+ qemu_iovec_memset(qiov, 0, 0, nb_sectors * BDRV_SECTOR_SIZE);
+ }
+
return null_aio_common(bs, cb, opaque);
}
--
2.7.4
- [Qemu-devel] [PATCH v2 0/4] qemu-img: Fix preallocation with -S 0 for convert, Max Reitz, 2016/03/24
- [Qemu-devel] [PATCH v2 1/4] qemu-img: Fix preallocation with -S 0 for convert, Max Reitz, 2016/03/24
- [Qemu-devel] [PATCH v2 3/4] block/null-{co, aio}: Implement get_block_status(), Max Reitz, 2016/03/24
- [Qemu-devel] [PATCH v2 2/4] block/null-{co, aio}: Allow reading zeroes,
Max Reitz <=
- [Qemu-devel] [PATCH v2 4/4] iotests: Test qemu-img convert -S 0 behavior, Max Reitz, 2016/03/24
- Re: [Qemu-devel] [PATCH v2 0/4] qemu-img: Fix preallocation with -S 0 for convert, Kevin Wolf, 2016/03/29