Re: [Qemu-devel] [PATCH v5 RESEND 3/4] raw-posix: Add full image preallocation option

[Hu Tao]

On Tue, Feb 11, 2014 at 05:04:09PM +0800, Fam Zheng wrote:
> On Tue, 02/11 15:07, Hu Tao wrote:
> > This patch adds a new option preallocation for raw format, and implements
> > full preallocation.
> > 
> > Signed-off-by: Hu Tao <address@hidden>
> > ---
> >  block/raw-posix.c | 43 +++++++++++++++++++++++++++++++++++--------
> >  1 file changed, 35 insertions(+), 8 deletions(-)
> > 
> > diff --git a/block/raw-posix.c b/block/raw-posix.c
> > index 01fb41a..1961b74 100644
> > --- a/block/raw-posix.c
> > +++ b/block/raw-posix.c
> > @@ -1229,11 +1229,22 @@ static int raw_create(const char *filename, 
> > QEMUOptionParameter *options,
> >      int fd;
> >      int result = 0;
> >      int64_t total_size = 0;
> > +    PreallocMode prealloc = PREALLOC_MODE_OFF;
> >  
> >      /* Read out options */
> >      while (options && options->name) {
> >          if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
> >              total_size = options->value.n & BDRV_SECTOR_MASK;
> > +        } else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) {
> > +            if (!options->value.s || !strcmp(options->value.s, "off")) {
> > +                prealloc = PREALLOC_MODE_OFF;
> > +            } else if (!strcmp(options->value.s, "full")) {
> > +                prealloc = PREALLOC_MODE_FULL;
> > +            } else {
> > +                error_setg(errp, "Invalid preallocation mode: '%s'",
> > +                           options->value.s);
> > +                return -EINVAL;
> > +            }
> >          }
> >          options++;
> >      }
> > @@ -1243,16 +1254,27 @@ static int raw_create(const char *filename, 
> > QEMUOptionParameter *options,
> >      if (fd < 0) {
> >          result = -errno;
> >          error_setg_errno(errp, -result, "Could not create file");
> > -    } else {
> > -        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 (ftruncate(fd, total_size) != 0) {
> > +        result = -errno;
> > +        error_setg_errno(errp, -result, "Could not resize file");
> > +        goto out_close;
> > +    }
> > +    if (prealloc == PREALLOC_MODE_FULL) {
> > +        /* 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");
> >          }
> >      }
> > +out_close:
> > +    if (qemu_close(fd) != 0) {
> > +        result = -errno;
> > +        error_setg_errno(errp, -result, "Could not close the new file");
> 
> If errp is already set because ftruncate or posix_ftruncate failed, and
> qemu_close() fails too, the call to error_setg_errno() will abort on failing
> the assertion of (*errp == NULL).

The original code also has the problem. This brings a general problem
that two error_setg_errno() could be called on the same errp. In general
the first error is better to reveal to user.

> 
> You could either embed the two failures in one error message, or pick the
> urgent one and drop the other.
> 
> Thanks,
> Fam
> 
> > +    }
> > +out:
> >      return result;
> >  }
> >  
> > @@ -1403,6 +1425,11 @@ static QEMUOptionParameter raw_create_options[] = {
> >          .type = OPT_SIZE,
> >          .help = "Virtual disk size"
> >      },
> > +    {
> > +        .name = BLOCK_OPT_PREALLOC,
> > +        .type = OPT_STRING,
> > +        .help = "Preallocation mode (allowed values: off, full)"
> > +    },
> >      { NULL }
> >  };
> >  
> > -- 
> > 1.8.0
> >