[Lustre-devel] Needed: insight on obd_set_info_async()

Andreas Dilger adilger at sun.com
Sun Oct 4 00:34:27 PDT 2009

On Oct 02, 2009  17:06 -0500, Nicolas Williams wrote:
> I'm trying to find out which uses of obd_set_info_async() involve values
> that come from a PTLRPC message buffer, and which ones don't.  It would
> help to know what obd_set_info_async() is for...  It seems it's a
> glorified ioctl()...

Sort of, yes, though I would characterize it more like a "get/set system
xattr".  It can get/set key,value pairs on a local or remote node.  The
"async" part means that the caller is the one in charge of handling waiting
for completion of the operation.  This is important when doing an operation
that may involve many OSTs, since we want the RPCs to happen in parallel
instead of in series.

> I'm tempted to augment it to always take a struct ptlrpc_request *req
> argument, so that req == NULL || val == NULL, and when req != NULL the
> value will be obtained using req_capsule_*_get().  Between that and
> enhancements to req_capsule_extend() and what not we might be able to
> ensure that 'val' is always swabbed by capsule code.

I can't comment on the HEAD capsule code, maybe someone else can...

> But if the uses of obd_set_info_async() are very clearly distinguishable
> it might be better to introduce a variant that takes a struct
> ptlrpc_request *req _instead_ of val/vallen.

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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