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raw-posix: Add falloc and full preallocation option

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This patch adds a new option preallocation for raw format, and implements
falloc and full preallocation.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Hu Tao 2014-09-10 17:05:48 +08:00 committed by Kevin Wolf
parent ffeaac9b4e
commit 06247428be
3 changed files with 96 additions and 24 deletions
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102
block/raw-posix.c
View file

@ -30,6 +30,7 @@
#include "block/thread-pool.h"
#include "qemu/iov.h"
#include "raw-aio.h"
#include "qapi/util.h"
#if defined(__APPLE__) && (__MACH__)
#include <paths.h>
@ -1365,6 +1366,9 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
int result = 0;
int64_t total_size = 0;
bool nocow = false;
PreallocMode prealloc;
char *buf = NULL;
Error *local_err = NULL;
strstart(filename, "file:", &filename);
@ -1372,37 +1376,82 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
BDRV_SECTOR_SIZE);
nocow = qemu_opt_get_bool(opts, BLOCK_OPT_NOCOW, false);
buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
prealloc = qapi_enum_parse(PreallocMode_lookup, buf,
PREALLOC_MODE_MAX, PREALLOC_MODE_OFF,
&local_err);
g_free(buf);
if (local_err) {
error_propagate(errp, local_err);
result = -EINVAL;
goto out;
}
fd = qemu_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
0644);
if (fd < 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not create file");
} else {
if (nocow) {
#ifdef __linux__
/* Set NOCOW flag to solve performance issue on fs like btrfs.
* This is an optimisation. The FS_IOC_SETFLAGS ioctl return value
* will be ignored since any failure of this operation should not
* block the left work.
*/
int attr;
if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
attr |= FS_NOCOW_FL;
ioctl(fd, FS_IOC_SETFLAGS, &attr);
}
#endif
}
if (ftruncate(fd, total_size) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
}
if (qemu_close(fd) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not close the new file");
}
goto out;
}
if (nocow) {
#ifdef __linux__
/* Set NOCOW flag to solve performance issue on fs like btrfs.
* This is an optimisation. The FS_IOC_SETFLAGS ioctl return value
* will be ignored since any failure of this operation should not
* block the left work.
*/
int attr;
if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
attr |= FS_NOCOW_FL;
ioctl(fd, FS_IOC_SETFLAGS, &attr);
}
#endif
}
if (ftruncate(fd, total_size) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
goto out_close;
}
if (prealloc == PREALLOC_MODE_FALLOC) {
/* posix_fallocate() doesn't set errno. */
result = -posix_fallocate(fd, 0, total_size);
if (result != 0) {
error_setg_errno(errp, -result,
"Could not preallocate data for the new file");
}
} else if (prealloc == PREALLOC_MODE_FULL) {
buf = g_malloc0(65536);
int64_t num = 0, left = total_size;
while (left > 0) {
num = MIN(left, 65536);
result = write(fd, buf, num);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
"Could not write to the new file");
break;
}
left -= num;
}
fsync(fd);
g_free(buf);
} else if (prealloc != PREALLOC_MODE_OFF) {
result = -EINVAL;
error_setg(errp, "Unsupported preallocation mode: %s",
PreallocMode_lookup[prealloc]);
}
out_close:
if (qemu_close(fd) != 0 && result == 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not close the new file");
}
out:
return result;
}
@ -1585,6 +1634,11 @@ static QemuOptsList raw_create_opts = {
.type = QEMU_OPT_BOOL,
.help = "Turn off copy-on-write (valid only on btrfs)"
},
{
.name = BLOCK_OPT_PREALLOC,
.type = QEMU_OPT_STRING,
.help = "Preallocation mode (allowed values: off, falloc, full)"
},
{ /* end of list */ }
}
};

9
qemu-doc.texi
View file

@ -527,6 +527,15 @@ Linux or NTFS on Windows), then only the written sectors will reserve
space. Use @code{qemu-img info} to know the real size used by the
image or @code{ls -ls} on Unix/Linux.
Supported options:
@table @code
@item preallocation
Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}).
@code{falloc} mode preallocates space for image by calling posix_fallocate().
@code{full} mode preallocates space for image by writing zeros to underlying
storage.
@end table
@item qcow2
QEMU image format, the most versatile format. Use it to have smaller
images (useful if your filesystem does not supports holes, for example

9
qemu-img.texi
View file

@ -419,6 +419,15 @@ Linux or NTFS on Windows), then only the written sectors will reserve
space. Use @code{qemu-img info} to know the real size used by the
image or @code{ls -ls} on Unix/Linux.
Supported options:
@table @code
@item preallocation
Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}).
@code{falloc} mode preallocates space for image by calling posix_fallocate().
@code{full} mode preallocates space for image by writing zeros to underlying
storage.
@end table
@item qcow2
QEMU image format, the most versatile format. Use it to have smaller
images (useful if your filesystem does not supports holes, for example