From: Josh Durgin <josh.dur...@inktank.com> Writeback caching was added in Ceph 0.46, and writethrough will be in 0.47. These are controlled by general config options, so there's no need to check for librbd version.
Signed-off-by: Josh Durgin <josh.dur...@inktank.com> Signed-off-by: Kevin Wolf <kw...@redhat.com> --- block/rbd.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) diff --git a/block/rbd.c b/block/rbd.c index 1280d66..eebc334 100644 --- a/block/rbd.c +++ b/block/rbd.c @@ -476,6 +476,25 @@ static int qemu_rbd_open(BlockDriverState *bs, const char *filename, int flags) s->snap = g_strdup(snap_buf); } + /* + * Fallback to more conservative semantics if setting cache + * options fails. Ignore errors from setting rbd_cache because the + * only possible error is that the option does not exist, and + * librbd defaults to no caching. If write through caching cannot + * be set up, fall back to no caching. + */ + if (flags & BDRV_O_NOCACHE) { + rados_conf_set(s->cluster, "rbd_cache", "false"); + } else { + rados_conf_set(s->cluster, "rbd_cache", "true"); + if (!(flags & BDRV_O_CACHE_WB)) { + r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0"); + if (r < 0) { + rados_conf_set(s->cluster, "rbd_cache", "false"); + } + } + } + if (strstr(conf, "conf=") == NULL) { /* try default location, but ignore failure */ rados_conf_read_file(s->cluster, NULL); -- 1.7.6.5