On Wed, 2024-02-07 at 14:58 -0500, Olga Kornievskaia wrote:

On Wed, Feb 7, 2024 at 2:51 PM Olga Kornievskaia
[off-list ref] wrote:

quoted

On Wed, Feb 7, 2024 at 2:12 PM Trond Myklebust
[off-list ref] wrote:

quoted

On Wed, 2024-02-07 at 13:29 -0500, Olga Kornievskaia wrote:

quoted

From: Olga Kornievskaia <redacted>

Currently, if the server returns a partial layout, the client
gets
stuck asking for a layout indefinitely. Until we add support
for
partial layouts, treat partial layout as layout unavailable
error.

Signed-off-by: Olga Kornievskaia <redacted>
---
 fs/nfs/nfs4proc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index dae4c1b6cc1c..108bc7f3e8c2 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c

@@ -9790,6 +9790,12 @@ nfs4_proc_layoutget(struct

nfs4_layoutget
*lgp,
      if (status != 0)
              goto out;

+     /* Since client does not support partial pnfs layout,
then
treat
+      * getting a partial layout as LAYOUTUNAVAILABLE error
+      */
+     if (lgp->args.range.length != lgp->res.range.length)
+             task->tk_status = -NFS4ERR_LAYOUTUNAVAILABLE;

I think this case is better handled by allowing the caller to set
lgp-

quoted

args.minlength to an appropriate minimum value.

I do not understand what this suggestion means. What I can think of
is
that the caller would set an appropriate minimum value and the code
here would check that the result is at least as large?

A follow up question on a "minimum value". It seems that since the
client would then need to set it to the same value as the "length"
(ie
whole file layout value), yes? So it shifts the responsibility to the
server, disallowing it from returning a partial layout.

quoted

If so, can you explain why that's more desirable? Seems to me it'd
be
more lines for something that would be removed later?

What I'm saying is that the protocol expects the client to send the
minimal acceptable layout length as a separate argument from the
desired length. Right now, we set the minimal length in
pnfs_alloc_init_layoutget_args() to be the smaller of PAGE_SIZE or the
length of the I/O segment.
The expectation is that all the pnfs drivers should be able to handle
that.

If you're telling me that there are drivers that do not handle being
given a layout with the minimal length that is set in
pnfs_alloc_init_layoutget_args(), then we should give them control over
that value.

quoted

quoted

quoted

+
      if (task->tk_status < 0) {
              exception->retry = 1;
              status = nfs4_layoutget_handle_exception(task,
lgp,
exception);

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com