On Tue, Feb 21, 2017 at 7:46 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > Hi Andreas- > > >> On Feb 20, 2017, at 4:31 PM, Andreas Gruenbacher <agruenba@xxxxxxxxxx> wrote: >> >> On Mon, Feb 20, 2017 at 6:15 PM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: >>> On Mon, Feb 20, 2017 at 11:42:31AM -0500, Chuck Lever wrote: >>>> >>>>> On Feb 20, 2017, at 11:09 AM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: >>>>> >>>>> On Sun, Feb 19, 2017 at 02:29:03PM -0500, Chuck Lever wrote: >>>>>> >>>>>>> On Feb 18, 2017, at 9:07 PM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: >>>>>>> >>>>>>> From: Weston Andros Adamson <dros@xxxxxxxxxx> >>>>>>> >>>>>>> Instead of preallocating pags, allow xdr_partial_copy_from_skb() to >>>>>>> allocate whatever pages we need on demand. This is what the NFSv3 ACL >>>>>>> code does. >>>>>> >>>>>> The patch description does not explain why this change is >>>>>> being done. >>>>> >>>>> The only justification I see is avoiding allocating pages unnecessarily. >>>> >>>> That makes sense. Is there a real world workload that has seen >>>> a negative effect? >>>> >>>> >>>>> Without this patch, for each getacl, we allocate 17 pages (if I'm >>>>> calculating correctly) and probably rarely use most of them. >>>>> >>>>> In the v3 case I think it's 7 pages instead of 17. >>>> >>>> I would have guessed 9. Out of curiosity, is there a reason >>>> documented for these size limits? >>> >>> >>> In the v4 case: >>> >>> #define NFS4ACL_MAXPAGES DIV_ROUND_UP(XATTR_SIZE_MAX, PAGE_SIZE) >>> >>> And I believe XATTR_SIZE_MAX is a global maximum on the size of any >>> extend attribute value. >> >> XATTR_SIZE_MAX is the maximum size of an extended attribute. NFSv4 >> ACLs are passed through unchanged in "system.nfs4_acl". > > "Extended attribute" means this is a Linux-specific limit? Yes. > Is there anything that prevents a non-Linux system from constructing > or returning an ACL that is larger than that? No. > What happens on a Linux client when a server returns an ACL that does > not fit in this allotment? I would hope an error, but I haven't tested it. Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
