[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Failed to read /local/domain/0/backend/qdisk/26/51713/feature-flush-cache.
On Thu, 2013-10-31 at 19:13 +0100, Samuel Thibault wrote: > Ian Campbell, le Thu 31 Oct 2013 15:14:59 +0000, a écrit : > > extras/mini-os/blkfront.c should deal with this. However it > > unconditionally uses BLKIF_OP_FLUSH_DISKCACHE in blkfront_sync, > > ? It checks for dev->info.flush being 1. Oh, I incorrectly read that as the request being to flush... > AFAIK the printed warning > does not have consequences by itself. > > > I'm not sure what the fallback (if any) is supposed to be. I doubt it > > can be safely ignored, but that might be the only/best option? > > Well, I don't know the precise semantic of missing barrier and cache > features. Normally it means (resp.) there is strict ordering of > operations, and no cache, but I doubt all implementations do that. I'm > indeed afraid there is no other option than what is already implemented. OK, so I also incorrectly read init_blkfront() and took the char path[strlen(dev->backend) + strlen("/feature-flush-cache") + 1]; snprintf(path, sizeof(path), "%s/mode", dev->backend); msg = xenbus_read(XBT_NIL, path, &c); if (msg) { printk("Error %s when reading the mode\n", msg); goto error; } to be erroring on reading feature-flush-cache, which it isn't... So far I'm 0/2, sorry. So, the upshot is that this is just a warning message and nothing to worry about. fanh2010, if you are really bothered by this warning perhaps a patch to make a variant of xenbus_read_integer which silently accepts ENOENT would be reasonable. (wait for Samuel to ack/nack the concept before putting in the effort though) Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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