> On Dec 3, 2020, at 3:39 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Thu, 2020-12-03 at 15:31 -0500, Anna Schumaker wrote: >> On Thu, Dec 3, 2020 at 3:27 PM Chuck Lever <chuck.lever@xxxxxxxxxx> >> wrote: >>> >>> >>> >>>> On Dec 3, 2020, at 3:18 PM, schumaker.anna@xxxxxxxxx wrote: >>>> >>>> From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> >>>> >>>> We might need this to better handle shifting around data in the >>>> reply >>>> buffer. >>>> >>>> Suggested-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> >>>> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> >>>> --- >>>> fs/nfs/nfs42xdr.c | 2 ++ >>>> fs/nfs/read.c | 13 +++++++++++-- >>>> include/linux/nfs_xdr.h | 1 + >>>> 3 files changed, 14 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c >>>> index 8432bd6b95f0..ef095a5f86f7 100644 >>>> --- a/fs/nfs/nfs42xdr.c >>>> +++ b/fs/nfs/nfs42xdr.c >>>> @@ -1297,6 +1297,8 @@ static int nfs4_xdr_dec_read_plus(struct >>>> rpc_rqst *rqstp, >>>> struct compound_hdr hdr; >>>> int status; >>>> >>>> + xdr_set_scratch_buffer(xdr, page_address(res->scratch), >>>> PAGE_SIZE); >>> >>> I intend to submit this for v5.11: >>> >>> https://git.linux-nfs.org/?p=cel/cel-2.6.git;a=commit;h=0ae4c3e8a64ace1b8d7de033b0751afe43024416 >> >> Thanks for the heads up! This patch can probably be deferred until >> yours goes in. >> >>> >>> But seems like enough callers need a scratch buffer that the XDR >>> layer should set up it transparently for all requests. >> >> That could work too, and save some headache. >> > > Why not just integrate it into xdr_init_decode_pages(), and then add a > matching xdr_exit_decode_pages() to free up any allocated page? Sounds OK. For comparison, to support xdr_stream decoding on the server, I've changed svc_rqst_alloc() to grab a page that stays around until the nfsd thread dies. There is a new svcxdr_init_decode() API that attaches that page for use as the decoding scratch buffer. Since it's a new API, the call sites that set up new streams with xdr_init_decode() are not affected. See: https://git.linux-nfs.org/?p=cel/cel-2.6.git;a=commit;h=5191955d6fc65e6d4efe8f4f10a6028298f57281 -- Chuck Lever
