nfs41: serialize first layoutget of a file

Per RFC 5661 Errata 3208:
| A client MAY always forget its layout state and associated
| layout stateid at any time (See also section 12.5.5.1).
| In such case, the client MUST use a non-layout stateid for the next
| LAYOUTGET operation. This will signal the server that the client has
| no more layouts on the file and its respective layout state can be
| released before issuing a new layout in response to LAYOUTGET.

In order to make such a signal unique to server, client needs to serialize
all layoutgets using non-layout stateid. We implement this by serializing
layoutgets when client has no layout segments at hand.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Tom Haynes <Thomas.Haynes@primarydata.com>

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index fa00b56..7e1bac1 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1288,6 +1288,7 @@ pnfs_update_layout(struct inode *ino,
        struct nfs_client *clp = server->nfs_client;
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_segment *lseg = NULL;
+       bool first;
 
        if (!pnfs_enabled_sb(NFS_SERVER(ino)))
                goto out;
@@ -1295,6 +1296,8 @@ pnfs_update_layout(struct inode *ino,
        if (pnfs_within_mdsthreshold(ctx, ino, iomode))
                goto out;
 
+lookup_again:
+       first = false;
        spin_lock(&ino->i_lock);
        lo = pnfs_find_alloc_layout(ino, ctx, gfp_flags);
        if (lo == NULL) {
@@ -1312,10 +1315,27 @@ pnfs_update_layout(struct inode *ino,
        if (pnfs_layout_io_test_failed(lo, iomode))
                goto out_unlock;
 
-       /* Check to see if the layout for the given range already exists */
-       lseg = pnfs_find_lseg(lo, &arg);
-       if (lseg)
-               goto out_unlock;
+       first = list_empty(&lo->plh_segs);
+       if (first) {
+               /* The first layoutget for the file. Need to serialize per
+                * RFC 5661 Errata 3208.
+                */
+               if (test_and_set_bit(NFS_LAYOUT_FIRST_LAYOUTGET,
+                                    &lo->plh_flags)) {
+                       spin_unlock(&ino->i_lock);
+                       wait_on_bit(&lo->plh_flags, NFS_LAYOUT_FIRST_LAYOUTGET,
+                                   TASK_UNINTERRUPTIBLE);
+                       pnfs_put_layout_hdr(lo);
+                       goto lookup_again;
+               }
+       } else {
+               /* Check to see if the layout for the given range
+                * already exists
+                */
+               lseg = pnfs_find_lseg(lo, &arg);
+               if (lseg)
+                       goto out_unlock;
+       }
 
        if (pnfs_layoutgets_blocked(lo, 0))
                goto out_unlock;
@@ -1343,6 +1363,13 @@ pnfs_update_layout(struct inode *ino,
        lseg = send_layoutget(lo, ctx, &arg, gfp_flags);
        atomic_dec(&lo->plh_outstanding);
 out_put_layout_hdr:
+       if (first) {
+               unsigned long *bitlock = &lo->plh_flags;
+
+               clear_bit_unlock(NFS_LAYOUT_FIRST_LAYOUTGET, bitlock);
+               smp_mb__after_atomic();
+               wake_up_bit(bitlock, NFS_LAYOUT_FIRST_LAYOUTGET);
+       }
        pnfs_put_layout_hdr(lo);
 out:
        dprintk("%s: inode %s/%llu pNFS layout segment %s for "

diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index c398821..4cf0d54 100644 (file)
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -95,6 +95,7 @@ enum {
        NFS_LAYOUT_ROC,                 /* some lseg had roc bit set */
        NFS_LAYOUT_RETURN,              /* Return this layout ASAP */
        NFS_LAYOUT_INVALID_STID,        /* layout stateid id is invalid */
+       NFS_LAYOUT_FIRST_LAYOUTGET,     /* Serialize first layoutget */
 };
 
 enum layoutdriver_policy_flags {