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Add support for qemu copy_on_read feature.

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When drives are added with this flag, reads from the backing file are
copied into the overlay, improving performance of reads to the same
area of disk (at the expense of local storage).  This is excellent for
reading remote / slow sources like HTTP.
This commit is contained in:
Richard W.M. Jones
2014-08-29 18:19:13 +01:00
parent 6a3147a5a0
commit 180e3c30de
7 changed files with 52 additions and 11 deletions
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15
generator/actions.ml
View File

@@ -1290,7 +1290,7 @@ not all belong to a single logical operating system
{ defaults with
name = "add_drive";
style = RErr, [String "filename"], [OBool "readonly"; OString "format"; OString "iface"; OString "name"; OString "label"; OString "protocol"; OStringList "server"; OString "username"; OString "secret"; OString "cachemode"; OString "discard"];
style = RErr, [String "filename"], [OBool "readonly"; OString "format"; OString "iface"; OString "name"; OString "label"; OString "protocol"; OStringList "server"; OString "username"; OString "secret"; OString "cachemode"; OString "discard"; OBool "copyonread"];
once_had_no_optargs = true;
blocking = false;
fish_alias = ["add"];
@@ -1538,6 +1538,15 @@ possible, but don't mind if it doesn't work.
=back
=item C<copyonread>
The boolean parameter C<copyonread> enables copy-on-read support.
This only affects disk formats which have backing files, and causes
reads to be stored in the overlay layer, speeding up multiple reads
of the same area of disk.
The default is false.
=back" };
{ defaults with
@@ -1580,7 +1589,7 @@ not part of the formal API and can be removed or changed at any time." };
{ defaults with
name = "add_domain";
style = RInt "nrdisks", [String "dom"], [OString "libvirturi"; OBool "readonly"; OString "iface"; OBool "live"; OBool "allowuuid"; OString "readonlydisk"; OString "cachemode"; OString "discard"];
style = RInt "nrdisks", [String "dom"], [OString "libvirturi"; OBool "readonly"; OString "iface"; OBool "live"; OBool "allowuuid"; OString "readonlydisk"; OString "cachemode"; OString "discard"; OBool "copyonread"];
fish_alias = ["domain"]; config_only = true;
shortdesc = "add the disk(s) from a named libvirt domain";
longdesc = "\
@@ -1672,7 +1681,7 @@ C<guestfs_add_drive_opts>." };
This interface is not quite baked yet. -- RWMJ 2010-11-11
{ defaults with
name = "add_libvirt_dom";
style = RInt "nrdisks", [Pointer ("virDomainPtr", "dom")], [Bool "readonly"; String "iface"; Bool "live"; String "readonlydisk"; OString "cachemode"; OString "discard"];
style = RInt "nrdisks", [Pointer ("virDomainPtr", "dom")], [Bool "readonly"; String "iface"; Bool "live"; String "readonlydisk"; OString "cachemode"; OString "discard"; OBool "copyonread"];
in_fish = false;
shortdesc = "add the disk(s) from a libvirt domain";
longdesc = "\

13
src/drives.c
View File

@@ -62,6 +62,7 @@ struct drive_create_data {
const char *disk_label;
const char *cachemode;
enum discard discard;
bool copyonread;
};
/* Compile all the regular expressions once when the shared library is
@@ -146,6 +147,7 @@ create_drive_file (guestfs_h *g,
drv->disk_label = data->disk_label ? safe_strdup (g, data->disk_label) : NULL;
drv->cachemode = data->cachemode ? safe_strdup (g, data->cachemode) : NULL;
drv->discard = data->discard;
drv->copyonread = data->copyonread;
if (data->readonly) {
if (create_overlay (g, drv) == -1) {
@@ -181,6 +183,7 @@ create_drive_non_file (guestfs_h *g,
drv->disk_label = data->disk_label ? safe_strdup (g, data->disk_label) : NULL;
drv->cachemode = data->cachemode ? safe_strdup (g, data->cachemode) : NULL;
drv->discard = data->discard;
drv->copyonread = data->copyonread;
if (data->readonly) {
if (create_overlay (g, drv) == -1) {
@@ -467,6 +470,7 @@ create_drive_dev_null (guestfs_h *g,
data->exportname = tmpfile;
data->discard = discard_disable;
data->copyonread = false;
return create_drive_file (g, data);
}
@@ -532,7 +536,7 @@ static char *
drive_to_string (guestfs_h *g, const struct drive *drv)
{
return safe_asprintf
(g, "%s%s%s%s protocol=%s%s%s%s%s%s%s%s%s%s",
(g, "%s%s%s%s protocol=%s%s%s%s%s%s%s%s%s%s%s",
drv->src.u.path,
drv->readonly ? " readonly" : "",
drv->src.format ? " format=" : "",
@@ -547,7 +551,8 @@ drive_to_string (guestfs_h *g, const struct drive *drv)
drv->cachemode ? " cache=" : "",
drv->cachemode ? : "",
drv->discard == discard_disable ? "" :
drv->discard == discard_enable ? " discard=enable" : " discard=besteffort");
drv->discard == discard_enable ? " discard=enable" : " discard=besteffort",
drv->copyonread ? " copyonread" : "");
}
/* Add struct drive to the g->drives vector at the given index. */
@@ -814,6 +819,10 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
else
data.discard = discard_disable;
data.copyonread =
optargs->bitmask & GUESTFS_ADD_DRIVE_OPTS_COPYONREAD_BITMASK
? optargs->copyonread : false;
if (data.readonly && data.discard == discard_enable) {
error (g, _("discard support cannot be enabled on read-only drives"));
free_drive_servers (data.servers, data.nr_servers);

2
src/guestfs-internal-frontend.h
View File

@@ -152,6 +152,8 @@ struct guestfs___add_libvirt_dom_argv {
const char *cachemode;
#define GUESTFS___ADD_LIBVIRT_DOM_DISCARD_BITMASK (UINT64_C(1)<<5)
const char *discard;
#define GUESTFS___ADD_LIBVIRT_DOM_COPYONREAD_BITMASK (UINT64_C(1)<<6)
int copyonread;
};
extern GUESTFS_DLL_PUBLIC int guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom, const struct guestfs___add_libvirt_dom_argv *optargs);

1
src/guestfs-internal.h
View File

@@ -262,6 +262,7 @@ struct drive {
char *disk_label;
char *cachemode;
enum discard discard;
bool copyonread;
};
/* Extra hv parameters (from guestfs_config). */

3
src/launch-direct.c
View File

@@ -528,7 +528,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
* the if=... at the end.
*/
param = safe_asprintf
(g, "file=%s%s,cache=%s%s%s%s%s%s,id=hd%zu",
(g, "file=%s%s,cache=%s%s%s%s%s%s%s,id=hd%zu",
escaped_file,
drv->readonly ? ",snapshot=on" : "",
drv->cachemode ? drv->cachemode : "writeback",
@@ -537,6 +537,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
drv->src.format ? drv->src.format : "",
drv->disk_label ? ",serial=" : "",
drv->disk_label ? drv->disk_label : "",
drv->copyonread ? ",copy-on-read=on" : "",
i);
}
else {

13
src/launch-libvirt.c
View File

@@ -817,7 +817,7 @@ static int construct_libvirt_xml_devices (guestfs_h *g, const struct libvirt_xml
static int construct_libvirt_xml_qemu_cmdline (guestfs_h *g, const struct libvirt_xml_params *params, xmlTextWriterPtr xo);
static int construct_libvirt_xml_disk (guestfs_h *g, const struct backend_libvirt_data *data, xmlTextWriterPtr xo, struct drive *drv, size_t drv_index);
static int construct_libvirt_xml_disk_target (guestfs_h *g, xmlTextWriterPtr xo, size_t drv_index);
static int construct_libvirt_xml_disk_driver_qemu (guestfs_h *g, const struct backend_libvirt_data *data, struct drive *drv, xmlTextWriterPtr xo, const char *format, const char *cachemode, enum discard discard);
static int construct_libvirt_xml_disk_driver_qemu (guestfs_h *g, const struct backend_libvirt_data *data, struct drive *drv, xmlTextWriterPtr xo, const char *format, const char *cachemode, enum discard discard, bool copyonread);
static int construct_libvirt_xml_disk_address (guestfs_h *g, xmlTextWriterPtr xo, size_t drv_index);
static int construct_libvirt_xml_disk_source_hosts (guestfs_h *g, xmlTextWriterPtr xo, const struct drive_source *src);
static int construct_libvirt_xml_disk_source_seclabel (guestfs_h *g, const struct backend_libvirt_data *data, xmlTextWriterPtr xo);
@@ -1277,7 +1277,7 @@ construct_libvirt_xml_disk (guestfs_h *g,
if (construct_libvirt_xml_disk_driver_qemu (g, data, drv,
xo, "qcow2", "unsafe",
discard_disable)
discard_disable, false)
== -1)
return -1;
}
@@ -1416,7 +1416,7 @@ construct_libvirt_xml_disk (guestfs_h *g,
if (construct_libvirt_xml_disk_driver_qemu (g, data, drv, xo, format,
drv->cachemode ? : "writeback",
drv->discard)
drv->discard, false)
== -1)
return -1;
}
@@ -1458,7 +1458,8 @@ construct_libvirt_xml_disk_driver_qemu (guestfs_h *g,
xmlTextWriterPtr xo,
const char *format,
const char *cachemode,
enum discard discard)
enum discard discard,
bool copyonread)
{
bool discard_unmap = false;
@@ -1492,6 +1493,8 @@ construct_libvirt_xml_disk_driver_qemu (guestfs_h *g,
attribute ("cache", cachemode);
if (discard_unmap)
attribute ("discard", "unmap");
if (copyonread)
attribute ("copy_on_read", "on");
} end_element ();
return 0;
@@ -1578,7 +1581,7 @@ construct_libvirt_xml_appliance (guestfs_h *g,
if (construct_libvirt_xml_disk_driver_qemu (g, params->data, NULL, xo,
"qcow2", "unsafe",
discard_disable) == -1)
discard_disable, false) == -1)
return -1;
if (construct_libvirt_xml_disk_address (g, xo, params->appliance_index)

16
src/libvirt-domain.c
View File

@@ -65,6 +65,7 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
const char *iface;
const char *cachemode;
const char *discard;
bool copyonread;
struct guestfs___add_libvirt_dom_argv optargs2 = { .bitmask = 0 };
libvirturi = optargs->bitmask & GUESTFS_ADD_DOMAIN_LIBVIRTURI_BITMASK
@@ -83,6 +84,8 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
? optargs->cachemode : NULL;
discard = optargs->bitmask & GUESTFS_ADD_DOMAIN_DISCARD_BITMASK
? optargs->discard : NULL;
copyonread = optargs->bitmask & GUESTFS_ADD_DOMAIN_COPYONREAD_BITMASK
? optargs->copyonread : false;
if (live && readonly) {
error (g, _("you cannot set both live and readonly flags"));
@@ -143,6 +146,10 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
optargs2.bitmask |= GUESTFS___ADD_LIBVIRT_DOM_DISCARD_BITMASK;
optargs2.discard = discard;
}
if (copyonread) {
optargs2.bitmask |= GUESTFS___ADD_LIBVIRT_DOM_COPYONREAD_BITMASK;
optargs2.copyonread = copyonread;
}
r = guestfs___add_libvirt_dom (g, dom, &optargs2);
@@ -179,6 +186,7 @@ guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
const char *iface;
const char *cachemode;
const char *discard;
bool copyonread;
int live;
/* Default for back-compat reasons: */
enum readonlydisk readonlydisk = readonlydisk_write;
@@ -220,6 +228,10 @@ guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
optargs->bitmask & GUESTFS___ADD_LIBVIRT_DOM_DISCARD_BITMASK
? optargs->discard : NULL;
copyonread =
optargs->bitmask & GUESTFS___ADD_LIBVIRT_DOM_COPYONREAD_BITMASK
? optargs->copyonread : false;
if (live && readonly) {
error (g, _("you cannot set both live and readonly flags"));
return -1;
@@ -289,6 +301,10 @@ guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
data.optargs.bitmask |= GUESTFS_ADD_DRIVE_OPTS_DISCARD_BITMASK;
data.optargs.discard = discard;
}
if (copyonread) {
data.optargs.bitmask |= GUESTFS_ADD_DRIVE_OPTS_COPYONREAD_BITMASK;
data.optargs.copyonread = copyonread;
}
/* Checkpoint the command line around the operation so that either
* all disks are added or none are added.