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

[Jeff Cody <jcody@redhat.com>]

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.

> +        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.

> +                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)?


-Jeff