[libvirt RFC] qemu_saveimage: only use wrapper when using --bypass-cache

[Ani Sinha]

On Tue, Apr 12, 2022 at 10:09 PM Ani Sinha <ani at anisinha.ca> wrote:

> On Tue, Apr 12, 2022 at 2:48 PM Claudio Fontana <cfontana at suse.de> wrote:
> >
> > align the "save" with the "restore" code,
> > by only using the wrapper when using --bypass-cache.
> >
> > This avoids a copy, resulting in better performance.
> >
> > Signed-off-by: Claudio Fontana <cfontana at suse.de>
> > ---
> >  src/qemu/qemu_saveimage.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/qemu/qemu_saveimage.c b/src/qemu/qemu_saveimage.c
> > index 4fd4c5cfcd..5ea1b2fbcc 100644
> > --- a/src/qemu/qemu_saveimage.c
> > +++ b/src/qemu/qemu_saveimage.c
> > @@ -289,8 +289,10 @@ qemuSaveImageCreate(virQEMUDriver *driver,
> >      if (qemuSecuritySetImageFDLabel(driver->securityManager, vm->def,
> fd) < 0)
> >          goto cleanup;
> >
> > -    if (!(wrapperFd = virFileWrapperFdNew(&fd, path, wrapperFlags)))
> > -        goto cleanup;
> > +    if ((flags & VIR_DOMAIN_SAVE_BYPASS_CACHE)) {
> > +        if (!(wrapperFd = virFileWrapperFdNew(&fd, path, wrapperFlags)))
> > +            goto cleanup;
> > +    }
>
> There is an obvious issue with this code. We are trying to close and
> free a file descriptor that we have not opened when
> VIR_DOMAIN_SAVE_BYPASS_CACHE is set in flags.


I meant *not* set in flags.


>
> >
> >      if (virQEMUSaveDataWrite(data, fd, path) < 0)
> >          goto cleanup;
> > --
> > 2.34.1
> >
>
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