[PATCH 2/6] NFSv4.1/pnfs: derive loga_maxcount from the LAYOUTGET reply buffer

The client advertises a fixed PNFS_LAYOUT_MAXSIZE (4096) in
loga_maxcount no matter what reply buffer it actually allocated.  The
two only happen to agree for layout drivers that cap
max_layoutget_response at a single page.  Block and SCSI layouts
allocate a session-sized reply buffer, yet still tell the server it
must not send more than 4KB of layout: a server whose extent list
encodes larger than a page returns NFS4ERR_TOOSMALL even though the
client has ample room to receive it.

Set loga_maxcount from the size of the page array allocated for the
reply.  The client never advertises more than it can receive, and any
future change to the reply buffer sizing automatically carries its
wire advertisement with it.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Benjamin Coddington <bcodding-F/[email protected]>
---
 fs/nfs/pnfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 10102bda6a38..88deefd45202 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1209,7 +1209,7 @@ pnfs_alloc_init_layoutget_args(struct inode *ino,
 				lgp->args.minlength = i_size - range->offset;
 		}
 	}
-	lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;
+	lgp->args.maxcount = lgp->args.layout.pglen;
 	pnfs_copy_range(&lgp->args.range, range);
 	lgp->args.type = server->pnfs_curr_ld->id;
 	lgp->args.inode = ino;
-- 
2.53.0