NFSv4.1: Deal with wraparound issues when updating the layout stateid

[deliverable/linux.git] / fs / nfs / pnfs.c

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index d737557747b91b82947ec2d1e9552a35d9fb9419..f1387e87513ff619bcea36117fc29795106ec559 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -549,6 +549,15 @@ pnfs_destroy_all_layouts(struct nfs_client *clp)
        }
 }
 
+/*
+ * Compare 2 layout stateid sequence ids, to see which is newer,
+ * taking into account wraparound issues.
+ */
+static bool pnfs_seqid_is_newer(u32 s1, u32 s2)
+{
+       return (s32)s1 - (s32)s2 > 0;
+}
+
 /* update lo->plh_stateid with new if is more recent */
 void
 pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
@@ -558,7 +567,7 @@ pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
 
        oldseq = be32_to_cpu(lo->plh_stateid.seqid);
        newseq = be32_to_cpu(new->seqid);
-       if ((int)(newseq - oldseq) > 0) {
+       if (list_empty(&lo->plh_segs) || pnfs_seqid_is_newer(newseq, oldseq)) {
                nfs4_stateid_copy(&lo->plh_stateid, new);
                if (update_barrier) {
                        u32 new_barrier = be32_to_cpu(new->seqid);
@@ -907,18 +916,19 @@ pnfs_find_alloc_layout(struct inode *ino,
 
        dprintk("%s Begin ino=%p layout=%p\n", __func__, ino, nfsi->layout);
 
-       if (nfsi->layout) {
-               pnfs_get_layout_hdr(nfsi->layout);
-               return nfsi->layout;
-       }
+       if (nfsi->layout != NULL)
+               goto out_existing;
        spin_unlock(&ino->i_lock);
        new = alloc_init_layout_hdr(ino, ctx, gfp_flags);
        spin_lock(&ino->i_lock);
 
-       if (likely(nfsi->layout == NULL))       /* Won the race? */
+       if (likely(nfsi->layout == NULL)) {     /* Won the race? */
                nfsi->layout = new;
-       else
-               pnfs_free_layout_hdr(new);
+               return new;
+       }
+       pnfs_free_layout_hdr(new);
+out_existing:
+       pnfs_get_layout_hdr(nfsi->layout);
        return nfsi->layout;
 }
 
@@ -1180,6 +1190,10 @@ pnfs_layout_process(struct nfs4_layoutget *lgp)
                dprintk("%s forget reply due to state\n", __func__);
                goto out_forget_reply;
        }
+
+       /* Done processing layoutget. Set the layout stateid */
+       pnfs_set_layout_stateid(lo, &res->stateid, false);
+
        init_lseg(lo, lseg);
        lseg->pls_range = res->range;
        pnfs_get_lseg(lseg);
@@ -1190,8 +1204,6 @@ pnfs_layout_process(struct nfs4_layoutget *lgp)
                set_bit(NFS_LAYOUT_ROC, &lo->plh_flags);
        }
 
-       /* Done processing layoutget. Set the layout stateid */
-       pnfs_set_layout_stateid(lo, &res->stateid, false);
        spin_unlock(&ino->i_lock);
        return lseg;
 out: