Re: [Qemu-devel] [Xen-devel] [PATCH RFC 1/3] xen_disk: handle disk files on ramfs/tmpfs

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Mon, Dec 31, 2012 at 01:16:12PM +0100, Roger Pau Monne wrote:
> Files that reside on ramfs or tmpfs cannot be opened with O_DIRECT,

That is not entirely true. There are patches floating around (LKML)
to make tmpfs/ramfs be able to do this.

> if first call to bdrv_open fails with errno = EINVAL, try a second
> call without BDRV_O_NOCACHE.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> Cc: xen-devel@lists.xen.org
> Cc: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>
> Cc: Anthony PERARD <anthony.perard@citrix.com>
> ---
>  hw/xen_disk.c |   16 +++++++++++++---
>  1 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
> index e6bb2f2..a159ee5 100644
> --- a/hw/xen_disk.c
> +++ b/hw/xen_disk.c
> @@ -562,7 +562,7 @@ static void blk_alloc(struct XenDevice *xendev)
>  static int blk_init(struct XenDevice *xendev)
>  {
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
> -    int index, qflags, info = 0;
> +    int index, qflags, info = 0, rc;
>  
>      /* read xenstore entries */
>      if (blkdev->params == NULL) {
> @@ -625,8 +625,18 @@ static int blk_init(struct XenDevice *xendev)
>          xen_be_printf(&blkdev->xendev, 2, "create new bdrv (xenbus setup)\n");
>          blkdev->bs = bdrv_new(blkdev->dev);
>          if (blkdev->bs) {
> -            if (bdrv_open(blkdev->bs, blkdev->filename, qflags,
> -                        bdrv_find_whitelisted_format(blkdev->fileproto)) != 0) {
> +            rc = bdrv_open(blkdev->bs, blkdev->filename, qflags,
> +                        bdrv_find_whitelisted_format(blkdev->fileproto));
> +            if (rc != 0 && errno == EINVAL) {
> +                /* Files on ramfs or tmpfs cannot be opened with O_DIRECT,
> +                 * remove the BDRV_O_NOCACHE flag, and try to open
> +                 * the file again.
> +                 */
> +                qflags &= ~BDRV_O_NOCACHE;
> +                rc = bdrv_open(blkdev->bs, blkdev->filename, qflags,
> +                        bdrv_find_whitelisted_format(blkdev->fileproto));
> +            }
> +            if (rc != 0) {
>                  bdrv_delete(blkdev->bs);
>                  blkdev->bs = NULL;
>              }
> -- 
> 1.7.7.5 (Apple Git-26)
> 
> 
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