pnfs: allow splicing pre-encoded pages into the layoutcommit args

Currently there is no XDR buffer space allocated for the per-layout driver
layoutcommit payload, which leads to server buffer overflows in the
blocklayout driver even under simple workloads.  As we can't do per-layout
sizes for XDR operations we'll have to splice a previously encoded list
of pages into the XDR stream, similar to how we handle ACL buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 57b5728e0b8e..8827ab130ed3 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1854,6 +1854,7 @@ void pnfs_cleanup_layoutcommit(struct nfs4_layoutcommit_data *data)
 int
 pnfs_layoutcommit_inode(struct inode *inode, bool sync)
 {
+        struct pnfs_layoutdriver_type *ld = NFS_SERVER(inode)->pnfs_curr_ld;
         struct nfs4_layoutcommit_data *data;
         struct nfs_inode *nfsi = NFS_I(inode);
         loff_t end_pos;
@@ -1904,6 +1905,20 @@ pnfs_layoutcommit_inode(struct inode *inode, bool sync)
         data->args.lastbytewritten = end_pos - 1;
         data->res.server = NFS_SERVER(inode);
 
+        if (ld->prepare_layoutcommit) {
+                status = ld->prepare_layoutcommit(&data->args);
+                if (status) {
+                        spin_lock(&inode->i_lock);
+                        if (end_pos < nfsi->layout->plh_lwb)
+                                nfsi->layout->plh_lwb = end_pos;
+                        spin_unlock(&inode->i_lock);
+                        put_rpccred(data->cred);
+                        set_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags);
+                        goto clear_layoutcommitting;
+                }
+        }
+
+
         status = nfs4_proc_layoutcommit(data, sync);
 out:
         if (status)