Messages in this thread | | | From | "Benjamin Coddington" <> | Subject | Re: Regression in 5.1.20: Reading long directory fails | Date | Sun, 08 Sep 2019 07:39:08 -0400 |
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On 6 Sep 2019, at 16:50, Chuck Lever wrote:
>> On Sep 6, 2019, at 4:47 PM, Jason L Tibbitts III <tibbs@math.uh.edu> >> wrote: >> >>>>>>> "JBF" == J Bruce Fields <bfields@fieldses.org> writes: >> >> JBF> Those readdir changes were client-side, right? Based on that >> I'd >> JBF> been assuming a client bug, but maybe it'd be worth getting a >> full >> JBF> packet capture of the readdir reply to make sure it's legit. >> >> I have been working with bcodding on IRC for the past couple of days >> on >> this. Fortunately I was able to come up with way to fill up a >> directory >> in such a way that it will fail with certainty and as a bonus doesn't >> include any user data so I can feel OK about sharing packet captures. >> I >> have a capture alongside a kernel trace of the problematic operation >> in >> https://www.math.uh.edu/~tibbs/nfs/. Not that I can particularly >> tell >> anything useful from that, but bcodding says that it seems to point >> to >> some issue in sunrpc. >> >> And because I can easily reproduce this and I was able to do a >> bisect: >> >> 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d is the first bad commit >> commit 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d >> Author: Chuck Lever <chuck.lever@oracle.com> >> Date: Mon Feb 11 11:25:41 2019 -0500 >> >> SUNRPC: Use au_rslack when computing reply buffer size >> >> au_rslack is significantly smaller than (au_cslack << 2). Using >> that value results in smaller receive buffers. In some cases this >> eliminates an extra segment in Reply chunks (RPC/RDMA). >> >> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> >> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> >> >> :040000 040000 d4d1ce2fbe0035c5bd9df976b8c448df85dcb505 >> 7011a792dfe72ff9cd70d66e45d353f3d7817e3e M net >> >> But of course, I can't say whether this is the actual bad commit or >> whether it just introduced a behavior change which alters the >> conditions >> under which the problem appears. > > The first place I'd start looking is the XDR constants at the head of > fs/nfs/nfs4xdr.c > having to do with READDIR. > > The report of behavior changes with the use of krb5p also makes this > commit plausible.
After sprinkling the printk's, we're coming up one word short in the receive buffer. I think we're not accounting for the xdr pad of buf->pages for NFS4 readdir -- but I need to check the RFCs. Anyone know if v4 READDIR results have to be aligned?
Also need to check just why krb5i is the only auth that cares..
Ben
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