gfs2: Update to the evict / remote delete documentation

Try to be a bit more clear and remove some duplications.  We cannot
actually get rid of the verification step eventually, so remove the
comment saying so.

Signed-off-by: Andreas Gruenbacher <[email protected]>

Author: Andreas Gruenbacher

fs/gfs2/glock.c

@@ -965,13 +965,16 @@ static void gfs2_try_evict(struct gfs2_glock *gl)
 
 	/*
 	 * If there is contention on the iopen glock and we have an inode, try
-	 * to grab and release the inode so that it can be evicted.  This will
-	 * allow the remote node to go ahead and delete the inode without us
-	 * having to do it, which will avoid rgrp glock thrashing.
+	 * to grab and release the inode so that it can be evicted.  The
+	 * GIF_DEFER_DELETE flag indicates to gfs2_evict_inode() that the inode
+	 * should not be deleted locally.  This will allow the remote node to
+	 * go ahead and delete the inode without us having to do it, which will
+	 * avoid rgrp glock thrashing.
 	 *
 	 * The remote node is likely still holding the corresponding inode
 	 * glock, so it will run before we get to verify that the delete has
-	 * happened below.
+	 * happened below.  (Verification is triggered by the call to
+	 * gfs2_queue_verify_delete() in gfs2_evict_inode().)
 	 */
 	spin_lock(&gl->gl_lockref.lock);
 	ip = gl->gl_object;
@@ -1027,26 +1030,8 @@ static void delete_work_func(struct work_struct *work)
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 	bool verify_delete = test_and_clear_bit(GLF_VERIFY_DELETE, &gl->gl_flags);
 
-	if (test_and_clear_bit(GLF_TRY_TO_EVICT, &gl->gl_flags)) {
-		/*
-		 * If we can evict the inode, give the remote node trying to
-		 * delete the inode some time before verifying that the delete
-		 * has happened.  Otherwise, if we cause contention on the inode glock
-		 * immediately, the remote node will think that we still have
-		 * the inode in use, and so it will give up waiting.
-		 *
-		 * If we can't evict the inode, signal to the remote node that
-		 * the inode is still in use.  We'll later try to delete the
-		 * inode locally in gfs2_evict_inode.
-		 *
-		 * FIXME: We only need to verify that the remote node has
-		 * deleted the inode because nodes before this remote delete
-		 * rework won't cooperate.  At a later time, when we no longer
-		 * care about compatibility with such nodes, we can skip this
-		 * step entirely.
-		 */
+	if (test_and_clear_bit(GLF_TRY_TO_EVICT, &gl->gl_flags))
 		gfs2_try_evict(gl);
-	}
 
 	if (verify_delete) {
 		u64 no_addr = gl->gl_name.ln_number;

fs/gfs2/super.c

@@ -1272,9 +1272,9 @@ static enum evict_behavior gfs2_upgrade_iopen_glock(struct inode *inode)
 	 * exclusive access to the iopen glock here.
 	 *
 	 * Otherwise, the other nodes holding the lock will be notified about
-	 * our locking request.  If they do not have the inode open, they are
-	 * expected to evict the cached inode and release the lock, allowing us
-	 * to proceed.
+	 * our locking request (see iopen_go_callback()).  If they do not have
+	 * the inode open, they are expected to evict the cached inode and
+	 * release the lock, allowing us to proceed.
 	 *
 	 * Otherwise, if they cannot evict the inode, they are expected to poke
 	 * the inode glock (note: not the iopen glock).  We will notice that