[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH] qcow2: Add full image preallocation option
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH] qcow2: Add full image preallocation option |
Date: |
Thu, 27 Jan 2011 16:52:14 +0100 |
This adds a preallocation=full mode to qcow2 image creation, which does not
only allocate metadata for the whole image, but also writes zeros to it,
creating a non-sparse image file.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index a1773e4..90cf2ca 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -838,7 +838,15 @@ static int qcow2_change_backing_file(BlockDriverState *bs,
return qcow2_update_ext_header(bs, backing_file, backing_fmt);
}
-static int preallocate(BlockDriverState *bs)
+enum prealloc_mode {
+ PREALLOC_OFF = 0,
+ PREALLOC_METADATA,
+ PREALLOC_FULL,
+};
+
+#define IO_BUF_SIZE (2 * 1024 * 1024)
+
+static int preallocate(BlockDriverState *bs, enum prealloc_mode mode)
{
uint64_t nb_sectors;
uint64_t offset;
@@ -846,11 +854,14 @@ static int preallocate(BlockDriverState *bs)
int ret;
QCowL2Meta meta;
+ assert(mode != PREALLOC_OFF);
+
nb_sectors = bdrv_getlength(bs) >> 9;
offset = 0;
QLIST_INIT(&meta.dependent_requests);
meta.cluster_offset = 0;
+ /* First allocate metadata in _really_ big chunks */
while (nb_sectors) {
num = MIN(nb_sectors, INT_MAX >> 9);
ret = qcow2_alloc_cluster_offset(bs, offset, 0, num, &num, &meta);
@@ -874,6 +885,28 @@ static int preallocate(BlockDriverState *bs)
offset += num << 9;
}
+ /* Then write zeros to the cluster data, if requested */
+ if (mode == PREALLOC_FULL) {
+ void *buf = qemu_mallocz(IO_BUF_SIZE);
+
+ nb_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
+ offset = 0;
+
+ while (nb_sectors) {
+ num = MIN(nb_sectors, IO_BUF_SIZE / BDRV_SECTOR_SIZE);
+ ret = bdrv_write(bs, offset >> BDRV_SECTOR_BITS, buf, num);
+ if (ret < 0) {
+ qemu_free(buf);
+ return ret;
+ }
+
+ nb_sectors -= num;
+ offset += num << 9;
+ }
+
+ qemu_free(buf);
+ }
+
/*
* It is expected that the image file is large enough to actually contain
* all of the allocated clusters (otherwise we get failing reads after
@@ -1006,7 +1039,7 @@ static int qcow2_create2(const char *filename, int64_t
total_size,
/* And if we're supposed to preallocate metadata, do that now */
if (prealloc) {
- ret = preallocate(bs);
+ ret = preallocate(bs, prealloc);
if (ret < 0) {
goto out;
}
@@ -1043,9 +1076,11 @@ static int qcow2_create(const char *filename,
QEMUOptionParameter *options)
}
} else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) {
if (!options->value.s || !strcmp(options->value.s, "off")) {
- prealloc = 0;
+ prealloc = PREALLOC_OFF;
} else if (!strcmp(options->value.s, "metadata")) {
- prealloc = 1;
+ prealloc = PREALLOC_METADATA;
+ } else if (!strcmp(options->value.s, "full")) {
+ prealloc = PREALLOC_FULL;
} else {
fprintf(stderr, "Invalid preallocation mode: '%s'\n",
options->value.s);
@@ -1336,7 +1371,7 @@ static QEMUOptionParameter qcow2_create_options[] = {
{
.name = BLOCK_OPT_PREALLOC,
.type = OPT_STRING,
- .help = "Preallocation mode (allowed values: off, metadata)"
+ .help = "Preallocation mode (allowed values: off, metadata, full)"
},
{ NULL }
};
--
1.7.2.3
- [Qemu-devel] [PATCH] qcow2: Add full image preallocation option,
Kevin Wolf <=