> On Mar 3, 2021, at 1:25 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Wed, Mar 03, 2021 at 06:19:33PM +0000, Chuck Lever wrote: >> >> >>> On Mar 3, 2021, at 11:52 AM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote: >>> >>> On Wed, Mar 03, 2021 at 03:43:28PM +0000, Chuck Lever wrote: >>>> Why would that not be OK? the next call to xdr_get_next_encode_buffer() >>>> should do the right thing and bounce the new encoded data from the >>>> next page into this one again. >>>> >>>> So far I have not encountered any problems. Would such a problem show >>>> up with some frequency under normal use, or would it be especially >>>> subtle? >>> >>> I mainly just want to make sure we've got a coherent idea what this code >>> is doing.... >> >> Agreed, that's a good thing. > > I'm also a little vague on what exactly the problem is you're running > into. (Probably because I haven't really looked at the v3 readdir > encoding.) > > Is it approaching the end of a page, or is it running out of buflen? > How exactly does it fail? I don't recall exactly, it was a late last summer when I wrote all these. Approaching the end of a page, IIRC, the unpatched code would leave a gap in the directory entry stream. > --b. > >> >> >>> For testing: large replies that aren't just read data are readdir and >>> getacl. So reading large directories with lots of variably-named files >>> might be good. Also pynfs could easily send a single compound with lots >>> of variable-sized reads, that might be interesting. >> >> I've run the full git regression suite over NFSv3 many many times with >> this patch applied. That includes unpacking via tar, a full build from >> scratch, and then running thousands of individual tests. >> >> So that doesn't exercise a particular corner case, but it does reflect >> a broad variety of directory operations. >> >> >>> Constructing a compound that will result in xdr_reserve_space calls that >>> exactly hit the various corner cases may be hard. But maybe if we just >>> send a bunch of compounds that vary over some range we can still >>> guarantee hitting those cases. >>> >>> --b. >> >> -- >> Chuck Lever -- Chuck Lever
