pNFS: Wait for stale layoutget calls to complete in pnfs_update_layout()

If the old layout was recalled, and we returned NFS4ERR_NOMATCHINGLAYOUT
then we need to wait for all outstanding layoutget calls to complete
before we can send a new one.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index bf7f0b21066deac733eeee694f5703b4e7f92a2e..030c39c107c21c498778538db1a3b0654cd6d1fd 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1740,6 +1740,17 @@ static bool pnfs_prepare_to_retry_layoutget(struct pnfs_layout_hdr *lo)
                                   TASK_UNINTERRUPTIBLE);
 }
 
+static void nfs_layoutget_begin(struct pnfs_layout_hdr *lo)
+{
+       atomic_inc(&lo->plh_outstanding);
+}
+
+static void nfs_layoutget_end(struct pnfs_layout_hdr *lo)
+{
+       if (atomic_dec_and_test(&lo->plh_outstanding))
+               wake_up_var(&lo->plh_outstanding);
+}
+
 static void pnfs_clear_first_layoutget(struct pnfs_layout_hdr *lo)
 {
        unsigned long *bitlock = &lo->plh_flags;
@@ -1839,6 +1850,21 @@ lookup_again:
                goto out_unlock;
        }
 
+       /*
+        * If the layout segment list is empty, but there are outstanding
+        * layoutget calls, then they might be subject to a layoutrecall.
+        */
+       if (list_empty(&lo->plh_segs) &&
+           atomic_read(&lo->plh_outstanding) != 0) {
+               spin_unlock(&ino->i_lock);
+               if (wait_var_event_killable(&lo->plh_outstanding,
+                                       atomic_read(&lo->plh_outstanding) == 0
+                                       || !list_empty(&lo->plh_segs)))
+                       goto out_put_layout_hdr;
+               pnfs_put_layout_hdr(lo);
+               goto lookup_again;
+       }
+
        lseg = pnfs_find_lseg(lo, &arg, strict_iomode);
        if (lseg) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
@@ -1912,7 +1938,7 @@ lookup_again:
                                PNFS_UPDATE_LAYOUT_BLOCKED);
                goto out_unlock;
        }
-       atomic_inc(&lo->plh_outstanding);
+       nfs_layoutget_begin(lo);
        spin_unlock(&ino->i_lock);
 
        _add_to_server_list(lo, server);
@@ -1929,14 +1955,14 @@ lookup_again:
        if (!lgp) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, NULL,
                                         PNFS_UPDATE_LAYOUT_NOMEM);
-               atomic_dec(&lo->plh_outstanding);
+               nfs_layoutget_end(lo);
                goto out_put_layout_hdr;
        }
 
        lseg = nfs4_proc_layoutget(lgp, &timeout);
        trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_SEND_LAYOUTGET);
-       atomic_dec(&lo->plh_outstanding);
+       nfs_layoutget_end(lo);
        if (IS_ERR(lseg)) {
                switch(PTR_ERR(lseg)) {
                case -EBUSY:
@@ -2031,7 +2057,7 @@ _pnfs_grab_empty_layout(struct inode *ino, struct nfs_open_context *ctx)
                goto out_unlock;
        if (test_and_set_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags))
                goto out_unlock;
-       atomic_inc(&lo->plh_outstanding);
+       nfs_layoutget_begin(lo);
        spin_unlock(&ino->i_lock);
        _add_to_server_list(lo, NFS_SERVER(ino));
        return lo;
@@ -2172,8 +2198,8 @@ void nfs4_lgopen_release(struct nfs4_layoutget *lgp)
                struct inode *inode = lgp->args.inode;
                if (inode) {
                        struct pnfs_layout_hdr *lo = NFS_I(inode)->layout;
-                       atomic_dec(&lo->plh_outstanding);
                        pnfs_clear_first_layoutget(lo);
+                       nfs_layoutget_end(lo);
                }
                pnfs_layoutget_free(lgp);
        }