[PATCH 2/7] pNFS: Don't allocate more pages than we need to fit a layoutget response

[Trond Myklebust <trondmy@gmail.com>]

For the 'files' and 'flexfiles' layout types, we do not expect the reply
to be any larger than 4k. The block and scsi layout types are a little more
greedy, so we keep allocating the maximum response size for now.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/filelayout/filelayout.c         | 1 +
 fs/nfs/flexfilelayout/flexfilelayout.c | 1 +
 fs/nfs/pnfs.c                          | 7 +++++++
 fs/nfs/pnfs.h                          | 1 +
 4 files changed, 10 insertions(+)

diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
index d175724ff566..61f46facb39c 100644
--- a/fs/nfs/filelayout/filelayout.c
+++ b/fs/nfs/filelayout/filelayout.c
@@ -1164,6 +1164,7 @@ static struct pnfs_layoutdriver_type filelayout_type = {
 	.id			= LAYOUT_NFSV4_1_FILES,
 	.name			= "LAYOUT_NFSV4_1_FILES",
 	.owner			= THIS_MODULE,
+	.max_layoutget_response	= 4096, /* 1 page or so... */
 	.alloc_layout_hdr	= filelayout_alloc_layout_hdr,
 	.free_layout_hdr	= filelayout_free_layout_hdr,
 	.alloc_lseg		= filelayout_alloc_lseg,
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index cae43333ef16..86bcba40ca61 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -2356,6 +2356,7 @@ static struct pnfs_layoutdriver_type flexfilelayout_type = {
 	.name			= "LAYOUT_FLEX_FILES",
 	.owner			= THIS_MODULE,
 	.flags			= PNFS_LAYOUTGET_ON_OPEN,
+	.max_layoutget_response	= 4096, /* 1 page or so... */
 	.set_layoutdriver	= ff_layout_set_layoutdriver,
 	.alloc_layout_hdr	= ff_layout_alloc_layout_hdr,
 	.free_layout_hdr	= ff_layout_free_layout_hdr,
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 6b5b2d36f502..c5672c02afd6 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -991,6 +991,7 @@ pnfs_alloc_init_layoutget_args(struct inode *ino,
 	   gfp_t gfp_flags)
 {
 	struct nfs_server *server = pnfs_find_server(ino, ctx);
+	size_t max_reply_sz = server->pnfs_curr_ld->max_layoutget_response;
 	size_t max_pages = max_response_pages(server);
 	struct nfs4_layoutget *lgp;
 
@@ -1000,6 +1001,12 @@ pnfs_alloc_init_layoutget_args(struct inode *ino,
 	if (lgp == NULL)
 		return NULL;
 
+	if (max_reply_sz) {
+		size_t npages = (max_reply_sz + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		if (npages < max_pages)
+			max_pages = npages;
+	}
+
 	lgp->args.layout.pages = nfs4_alloc_pages(max_pages, gfp_flags);
 	if (!lgp->args.layout.pages) {
 		kfree(lgp);
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index ece367ebde69..e2e9fcd5341d 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -125,6 +125,7 @@ struct pnfs_layoutdriver_type {
 	struct module *owner;
 	unsigned flags;
 	unsigned max_deviceinfo_size;
+	unsigned max_layoutget_response;
 
 	int (*set_layoutdriver) (struct nfs_server *, const struct nfs_fh *);
 	int (*clear_layoutdriver) (struct nfs_server *);
-- 
2.17.1