[RFC PATCH 0/2] Move rq_vec[] and rq_bvec[] out of svc_rqst

[cel@kernel.org]

From: Chuck Lever <chuck.lever@oracle.com>

In order to make RPCSVC_MAXPAYLOAD larger (or variable in size), we
need to do something clever with the payload arrays embedded in
struct svc_rqst. Here's one way of dealing with two of them.

My preference is to keep these arrays allocated all the time because
allocating them on demand increases the risk of a memory allocation
failure during a large I/O. This is a quick-and-dirty approach that
might be replaced once NFSD is converted to use large folios.

The downside of this design choice is that it pins a few pages per
NFSD thread (and that's the current situation already). But note
that because RPCSVC_MAXPAGES is 259, each array is just over a page
in size, making the allocation waste quite a bit of memory beyond
the end of the array due to power-of-2 allocator round up. This gets
worse as the MAXPAGES value is doubled or quadrupled.

I plan to look at rq_pages[] next.

Chuck Lever (2):
  sunrpc: Replace the rq_bvec array with dynamically-allocated memory
  sunrpc: Replace the rq_vec array with dynamically-allocated memory

 fs/nfsd/nfs4proc.c         |  2 +-
 fs/nfsd/vfs.c              |  2 +-
 include/linux/sunrpc/svc.h |  4 ++--
 net/sunrpc/svc.c           | 14 +++++++++++++-
 net/sunrpc/svcsock.c       |  7 +++----
 5 files changed, 20 insertions(+), 9 deletions(-)

-- 
2.49.0