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Re: [Qemu-devel] [PATCH] xen_disk: support cache backend option
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] [PATCH] xen_disk: support cache backend option |
Date: |
Wed, 26 Jun 2013 15:58:59 -0500 |
User-agent: |
Notmuch/0.15.2+77~g661dcf8 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Stefano Stabellini <address@hidden> writes:
> Support a backend option "cache" that specifies the cache mode that
> should be used to open the disk file or device.
>
> See: http://marc.info/?l=xen-devel&m=137226872905057
>
> Signed-off-by: Stefano Stabellini <address@hidden>
Is the guest setting this or a management tool? I thought we were
moving to having the Xen management tools use QMP and the command line
instead of putting this stuff in XenStore...
Regards,
Anthony Liguori
>
> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
> index f484404..092aa6b 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -94,6 +94,7 @@ struct XenBlkDev {
> char *type;
> char *dev;
> char *devtype;
> + char *cache;
> const char *fileproto;
> const char *filename;
> int ring_ref;
> @@ -734,6 +735,12 @@ static int blk_init(struct XenDevice *xendev)
> if (blkdev->devtype == NULL) {
> blkdev->devtype = xenstore_read_be_str(&blkdev->xendev,
> "device-type");
> }
> + if (blkdev->cache == NULL) {
> + blkdev->cache = xenstore_read_be_str(&blkdev->xendev, "cache");
> + }
> + if (blkdev->cache == NULL) {
> + blkdev->cache = g_strdup("writeback");
> + }
>
> /* do we have all we need? */
> if (blkdev->params == NULL ||
> @@ -774,6 +781,8 @@ out_error:
> blkdev->dev = NULL;
> g_free(blkdev->devtype);
> blkdev->devtype = NULL;
> + g_free(blkdev->cache);
> + blkdev->cache = NULL;
> return -1;
> }
>
> @@ -782,8 +791,14 @@ static int blk_connect(struct XenDevice *xendev)
> struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev,
> xendev);
> int pers, index, qflags;
>
> - /* read-only ? */
> - qflags = BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
> + if (!strcmp(blkdev->cache, "none")) {
> + qflags = BDRV_O_NATIVE_AIO | BDRV_O_NOCACHE;
> + } else if (!strcmp(blkdev->cache, "writethrough")) {
> + qflags = 0;
> + } else {
> + /* default to writeback */
> + qflags = BDRV_O_NATIVE_AIO | BDRV_O_CACHE_WB;
> + }
> if (strcmp(blkdev->mode, "w") == 0) {
> qflags |= BDRV_O_RDWR;
> }
> @@ -950,6 +965,7 @@ static int blk_free(struct XenDevice *xendev)
> g_free(blkdev->type);
> g_free(blkdev->dev);
> g_free(blkdev->devtype);
> + g_free(blkdev->cache);
> qemu_bh_delete(blkdev->bh);
> return 0;
> }