1 files changed, 20 insertions, 0 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index 34852ece4057..1b24ad07d4f5 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -160,6 +160,22 @@ static struct pnfs_layout_hdr * get_layout_by_fh(struct nfs_client *clp,
         return lo;
 }
 
+/*
+ * Enforce RFC5661 section 12.5.5.2.1. (Layout Recall and Return Sequencing)
+ */
+static bool pnfs_check_stateid_sequence(struct pnfs_layout_hdr *lo,
+                                        const nfs4_stateid *new)
+{
+        u32 oldseq, newseq;
+
+        oldseq = be32_to_cpu(lo->plh_stateid.seqid);
+        newseq = be32_to_cpu(new->seqid);
+
+        if (newseq > oldseq + 1)
+                return false;
+        return true;
+}
+
 static u32 initiate_file_draining(struct nfs_client *clp,
                                   struct cb_layoutrecallargs *args)
 {
@@ -175,6 +191,10 @@ static u32 initiate_file_draining(struct nfs_client *clp,
         ino = lo->plh_inode;
 
         spin_lock(&ino->i_lock);
+        if (!pnfs_check_stateid_sequence(lo, &args->cbl_stateid)) {
+                rv = NFS4ERR_DELAY;
+                goto unlock;
+        }
         pnfs_set_layout_stateid(lo, &args->cbl_stateid, true);
         spin_unlock(&ino->i_lock);