Re: [Qemu-devel] [PATCH V5 2/5] qemu-nbd: support internal snapshot export

[Wenchao Xia]

于 2013/11/19 19:26, Kevin Wolf 写道:
> Am 10.11.2013 um 23:03 hat Wenchao Xia geschrieben:
> > Now it is possible to directly export an internal snapshot, which
> > can be used to probe the snapshot's contents without qemu-img
> > convert.
> >
> > Signed-off-by: Wenchao Xia <address@hidden>
> > ---
> >   block/snapshot.c         |   18 +++++++++++++++++
> >   include/block/snapshot.h |    8 +++++++
> >   qemu-nbd.c               |   47 ++++++++++++++++++++++++++++++++++++++++++++-
> >   qemu-nbd.texi            |    8 ++++++-
> >   4 files changed, 78 insertions(+), 3 deletions(-)
> >
> > diff --git a/block/snapshot.c b/block/snapshot.c
> > index e51a7db..7cc45fa 100644
> > --- a/block/snapshot.c
> > +++ b/block/snapshot.c
> > @@ -25,6 +25,24 @@
> >   #include "block/snapshot.h"
> >   #include "block/block_int.h"
> >
> > +QemuOptsList internal_snapshot_opts = {
> > +    .name = "snapshot",
> > +    .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
> > +    .desc = {
> > +        {
> > +            .name = SNAPSHOT_OPT_ID,
> > +            .type = QEMU_OPT_STRING,
> > +            .help = "snapshot id"
> > +        },{
> > +            .name = SNAPSHOT_OPT_NAME,
> > +            .type = QEMU_OPT_STRING,
> > +            .help = "snapshot name"
> > +        },{
> > +            /* end of list */
> > +        }
> > +    },
> > +};
> > +
> >   int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
> >                          const char *name)
> >   {
> > diff --git a/include/block/snapshot.h b/include/block/snapshot.h
> > index d05bea7..770d9bb 100644
> > --- a/include/block/snapshot.h
> > +++ b/include/block/snapshot.h
> > @@ -27,6 +27,14 @@
> >
> >   #include "qemu-common.h"
> >   #include "qapi/error.h"
> > +#include "qemu/option.h"
> > +
> > +
> > +#define SNAPSHOT_OPT_BASE       "snapshot."
> > +#define SNAPSHOT_OPT_ID         "snapshot.id"
> > +#define SNAPSHOT_OPT_NAME       "snapshot.name"
> > +
> > +extern QemuOptsList internal_snapshot_opts;
> >
> >   typedef struct QEMUSnapshotInfo {
> >       char id_str[128]; /* unique snapshot id */
> > diff --git a/qemu-nbd.c b/qemu-nbd.c
> > index c26c98e..f934eaa 100644
> > --- a/qemu-nbd.c
> > +++ b/qemu-nbd.c
> > @@ -20,6 +20,7 @@
> >   #include "block/block.h"
> >   #include "block/nbd.h"
> >   #include "qemu/main-loop.h"
> > +#include "block/snapshot.h"
> >
> >   #include <stdarg.h>
> >   #include <stdio.h>
> > @@ -79,7 +80,14 @@ static void usage(const char *name)
> >   "\n"
> >   "Block device options:\n"
> >   "  -r, --read-only      export read-only\n"
> > -"  -s, --snapshot       use snapshot file\n"
> > +"  -s, --snapshot       use FILE as an external snapshot, create a temporary\n"
> > +"                       file with backing_file=FILE, redirect the write to\n"
> > +"                       the temporary one\n"
> > +"  -l, --load-snapshot=SNAPSHOT_PARAM\n"
> > +"                       load an internal snapshot inside FILE and export it\n"
> > +"                       as an read-only device, SNAPSHOT_PARAM format is\n"
> > +"                       'snapshot.id=[ID],snapshot.name=[NAME]', or\n"
> > +"                       '[ID_OR_NAME]'\n"
> >   "  -n, --nocache        disable host cache\n"
> >   "      --cache=MODE     set cache mode (none, writeback, ...)\n"
> >   #ifdef CONFIG_LINUX_AIO
> > @@ -315,7 +323,9 @@ int main(int argc, char **argv)
> >       char *device = NULL;
> >       int port = NBD_DEFAULT_PORT;
> >       off_t fd_size;
> > -    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:t";
> > +    QemuOpts *sn_opts = NULL;
> > +    const char *sn_id_or_name = NULL;
> > +    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
> >       struct option lopt[] = {
> >           { "help", 0, NULL, 'h' },
> >           { "version", 0, NULL, 'V' },
> > @@ -328,6 +338,7 @@ int main(int argc, char **argv)
> >           { "connect", 1, NULL, 'c' },
> >           { "disconnect", 0, NULL, 'd' },
> >           { "snapshot", 0, NULL, 's' },
> > +        { "load-snapshot", 1, NULL, 'l' },
> >           { "nocache", 0, NULL, 'n' },
> >           { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
> >   #ifdef CONFIG_LINUX_AIO
> > @@ -428,6 +439,18 @@ int main(int argc, char **argv)
> >                   errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
> >               }
> >               break;
> > +        case 'l':
> > +            if (strncmp(optarg, SNAPSHOT_OPT_BASE, strlen(SNAPSHOT_OPT_BASE))
> > +                == 0) {
>
> You can avoid this ugly line break by using strstart():
>
>      if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
>          ...
>
> Kevin
  Will use strstart(), thanks for tipping.