[PATCH 11/11] nfs: use wait_var_event_spinlock() to wait for nfsi->layout to change.

[NeilBrown <neilb@suse.de>]

The recently added interface wait_var_event_spinlock() is designed for
waiting for events that can only be checked under a spinlock.
This matches the requirements for waiting for nfsi->layout so we can
change to using wait_var_event_spinlock().

This avoids a use of plain wake_up_var() which always needs to be
checked for correct barrier usage.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/pnfs.c | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 400f409f45fa..04be1165a1c5 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -306,7 +306,6 @@ void
 pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
 {
 	struct inode *inode;
-	unsigned long i_state;
 
 	if (!lo)
 		return;
@@ -317,12 +316,11 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
 		if (!list_empty(&lo->plh_segs))
 			WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n");
 		pnfs_detach_layout_hdr(lo);
-		i_state = inode->i_state;
+		/* Notify pnfs_destroy_layout_final() that we're done */
+		if (inode->i_state & (I_FREEING | I_CLEAR))
+			wake_up_var_locked(lo, &inode->i_lock);
 		spin_unlock(&inode->i_lock);
 		pnfs_free_layout_hdr(lo);
-		/* Notify pnfs_destroy_layout_final() that we're done */
-		if (i_state & (I_FREEING | I_CLEAR))
-			wake_up_var(lo);
 	}
 }
 
@@ -795,23 +793,16 @@ void pnfs_destroy_layout(struct nfs_inode *nfsi)
 }
 EXPORT_SYMBOL_GPL(pnfs_destroy_layout);
 
-static bool pnfs_layout_removed(struct nfs_inode *nfsi,
-				struct pnfs_layout_hdr *lo)
-{
-	bool ret;
-
-	spin_lock(&nfsi->vfs_inode.i_lock);
-	ret = nfsi->layout != lo;
-	spin_unlock(&nfsi->vfs_inode.i_lock);
-	return ret;
-}
-
 void pnfs_destroy_layout_final(struct nfs_inode *nfsi)
 {
 	struct pnfs_layout_hdr *lo = __pnfs_destroy_layout(nfsi);
 
-	if (lo)
-		wait_var_event(lo, pnfs_layout_removed(nfsi, lo));
+	if (lo) {
+		spin_lock(&nfsi->vfs_inode.i_lock);
+		wait_var_event_spinlock(lo, nfsi->layout != lo,
+					&nfsi->vfs_inode.i_lock);
+		spin_unlock(&nfsi->vfs_inode.i_lock);
+	}
 }
 
 static bool
-- 
2.47.0