Re: [Qemu-devel] [PATCH] gluster: add support for PREALLOC_MODE_FALLOC

[Niels de Vos <ndevos@redhat.com>]

On Tue, May 16, 2017 at 11:42:37AM -0400, Jeff Cody wrote:
> On Mon, May 15, 2017 at 09:11:36PM +0200, Niels de Vos wrote:
> > Add missing support for "preallocation=falloc" to the Gluster block
> > driver. This change bases its logic on that of block/file-posix.c and
> > removed the gluster_supports_zerofill() function in favour of an #ifdef
> > check in an easy to read switch-statement.
> > 
> > Reported-by: Satheesaran Sundaramoorthi <sasundar@redhat.com>
> > URL: https://bugzilla.redhat.com/1450759
> > Signed-off-by: Niels de Vos <ndevos@redhat.com>
> > ---
> >  block/gluster.c | 61 +++++++++++++++++++++++++++++++++++----------------------
> >  1 file changed, 38 insertions(+), 23 deletions(-)
> > 
> > diff --git a/block/gluster.c b/block/gluster.c
> > index 7c76cd0..566166f 100644
> > --- a/block/gluster.c
> > +++ b/block/gluster.c
> > @@ -965,11 +965,6 @@ static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
> >      return acb.ret;
> >  }
> >  
> > -static inline bool gluster_supports_zerofill(void)
> > -{
> > -    return 1;
> > -}
> > -
> >  static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset,
> >                                          int64_t size)
> >  {
> > @@ -977,11 +972,6 @@ static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset,
> >  }
> >  
> >  #else
> > -static inline bool gluster_supports_zerofill(void)
> > -{
> > -    return 0;
> > -}
> > -
> >  static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset,
> >                                          int64_t size)
> >  {
> > @@ -996,9 +986,10 @@ static int qemu_gluster_create(const char *filename,
> >      struct glfs *glfs;
> >      struct glfs_fd *fd;
> >      int ret = 0;
> > -    int prealloc = 0;
> > +    PreallocMode prealloc;
> >      int64_t total_size = 0;
> >      char *tmp = NULL;
> > +    Error *local_err = NULL;
> >  
> >      gconf = g_new0(BlockdevOptionsGluster, 1);
> >      gconf->debug = qemu_opt_get_number_del(opts, GLUSTER_OPT_DEBUG,
> > @@ -1026,13 +1017,12 @@ static int qemu_gluster_create(const char *filename,
> >                            BDRV_SECTOR_SIZE);
> >  
> >      tmp = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
> > -    if (!tmp || !strcmp(tmp, "off")) {
> > -        prealloc = 0;
> > -    } else if (!strcmp(tmp, "full") && gluster_supports_zerofill()) {
> > -        prealloc = 1;
> > -    } else {
> > -        error_setg(errp, "Invalid preallocation mode: '%s'"
> > -                         " or GlusterFS doesn't support zerofill API", tmp);
> > +    prealloc = qapi_enum_parse(PreallocMode_lookup, tmp,
> > +                               PREALLOC_MODE__MAX, PREALLOC_MODE_OFF,
> > +                               &local_err);
> > +    g_free(tmp);
> > +    if (local_err) {
> > +        error_propagate(errp, local_err);
> >          ret = -EINVAL;
> >          goto out;
> >      }
> > @@ -1041,21 +1031,46 @@ static int qemu_gluster_create(const char *filename,
> >                      O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR | S_IWUSR);
> >      if (!fd) {
> >          ret = -errno;
> > -    } else {
> > +        goto out;
> > +    }
> > +
> > +    switch (prealloc) {
> > +    case PREALLOC_MODE_FALLOC:
> > +        if (!glfs_fallocate(fd, 0, 0, total_size)) {
> > +            error_setg(errp, "Could not preallocate data for the new file");
> > +            ret = -errno;
> > +        }
> 
> Both glfs_fallocate() and glfs_zerofill() are from the same release version,
> right?  I think we need a CONFIG_GLUSTER_FALLOC around the
> PREALLOC_MODE_FALLOC case, just like CONFIG_GLUSTERFS_ZEROFILL.

Yes, both were added at the same GlusterFS release. I'll add the check
in ./configure and #ifdef it.

> > +        break;
> > +#ifdef CONFIG_GLUSTERFS_ZEROFILL
> > +    case PREALLOC_MODE_FULL:
> >          if (!glfs_ftruncate(fd, total_size)) {
> > -            if (prealloc && qemu_gluster_zerofill(fd, 0, total_size)) {
> > +            if (qemu_gluster_zerofill(fd, 0, total_size)) {
> 
> If using the CONFIG_GLUSTER_ZEROFILL here, then please get rid of the
> qemu_gluster_zerofill() wrapper, which is in place for the same reason as
> this ifdef.  We can just call glfs_zerofill() here directly.

Right, will do!

> > +                error_setg(errp, "Could not zerofill the new file");
> >                  ret = -errno;
> >              }
> >          } else {
> > +            error_setg(errp, "Could not resize file");
> >              ret = -errno;
> >          }
> > -
> > -        if (glfs_close(fd) != 0) {
> > +        break;
> > +#endif /* CONFIG_GLUSTERFS_ZEROFILL */
> > +    case PREALLOC_MODE_OFF:
> > +        if (glfs_ftruncate(fd, total_size) != 0) {
> >              ret = -errno;
> > +            error_setg(errp, "Could not resize file");
> >          }
> > +        break;
> > +    default:
> > +        ret = -EINVAL;
> > +        error_setg(errp, "Unsupported preallocation mode: %s",
> > +                   PreallocMode_lookup[prealloc]);
> > +        break;
> > +    }
> > +
> > +    if (glfs_close(fd) != 0) {
> > +        ret = -errno;
> >      }
> >  out:
> > -    g_free(tmp);
> >      qapi_free_BlockdevOptionsGluster(gconf);
> >      glfs_clear_preopened(glfs);
> 
> A question that doesn't have to do with this patch: is it safe to call
> glfs_clear_preopened(NULL)?

glfs_clear_preopened() actually is a function that has its
implementation in block/gluster.c. Yes, it can accept NULL and will
return immediately.

Thanks,
Niels