pnfs: avoid incorrect use of layout stateid

The code could violate the following from RFC5661, section 12.5.3:
"Once a client has no more layouts on a file, the layout stateid is no
longer valid and MUST NOT be used."

This can occur when a layout already has a lseg, starts another
non-everlapping LAYOUTGET, and a CB_LAYOUTRECALL for the existing lseg
is processed before we hit pnfs_layout_process().

Solve by setting, each time the client has no more lsegs for a file, a
flag which blocks further use of the layout and triggers its removal.

This also fixes a second bug which occurs in the same instance as
above.  If we actually use pnfs_layout_process, we add the new lseg to
the layout, but the layout has been removed from the nfs_client list
by the intervening CB_LAYOUTRECALL and will not be added back.  Thus
the newly acquired lseg will not be properly returned in the event of
a subsequent CB_LAYOUTRECALL.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 1b1bc1a0fb0a..c8d9b2148cb1 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -255,6 +255,9 @@ put_lseg_locked(struct pnfs_layout_segment *lseg,
                         list_del_init(&lseg->pls_layout->plh_layouts);
                         spin_unlock(&clp->cl_lock);
                         clear_bit(NFS_LAYOUT_BULK_RECALL, &lseg->pls_layout->plh_flags);
+                        set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);
+                        /* Matched by initial refcount set in alloc_init_layout_hdr */
+                        put_layout_hdr_locked(lseg->pls_layout);
                 }
                 rpc_wake_up(&NFS_SERVER(ino)->roc_rpcwaitq);
                 list_add(&lseg->pls_list, tmp_list);
@@ -299,6 +302,11 @@ mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
 
         dprintk("%s:Begin lo %p\n", __func__, lo);
 
+        if (list_empty(&lo->plh_segs)) {
+                if (!test_and_set_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags))
+                        put_layout_hdr_locked(lo);
+                return 0;
+        }
         list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
                 if (should_free_lseg(lseg->pls_range.iomode, iomode)) {
                         dprintk("%s: freeing lseg %p iomode %d "
@@ -332,10 +340,8 @@ pnfs_destroy_layout(struct nfs_inode *nfsi)
         spin_lock(&nfsi->vfs_inode.i_lock);
         lo = nfsi->layout;
         if (lo) {
-                set_bit(NFS_LAYOUT_DESTROYED, &nfsi->layout->plh_flags);
+                lo->plh_block_lgets++; /* permanently block new LAYOUTGETs */
                 mark_matching_lsegs_invalid(lo, &tmp_list, IOMODE_ANY);
-                /* Matched by refcount set to 1 in alloc_init_layout_hdr */
-                put_layout_hdr_locked(lo);
         }
         spin_unlock(&nfsi->vfs_inode.i_lock);
         pnfs_free_lseg_list(&tmp_list);
@@ -403,6 +409,7 @@ pnfs_layoutgets_blocked(struct pnfs_layout_hdr *lo, nfs4_stateid *stateid,
             (int)(lo->plh_barrier - be32_to_cpu(stateid->stateid.seqid)) >= 0)
                 return true;
         return lo->plh_block_lgets ||
+                test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags) ||
                 test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags) ||
                 (list_empty(&lo->plh_segs) &&
                  (atomic_read(&lo->plh_outstanding) > lget));