gfs2: Add new go_held glock operation

Right now, inode_go_instantiate() contains functionality that relates to
how a glock is held rather than the glock itself, like waiting for
pending direct I/O to complete and completing interrupted truncates.
This code is meant to be run each time a holder is acquired, but
go_instantiate is actually only called once, when the glock is
instantiated.

To fix that, introduce a new go_held glock operation that is called each
time a glock holder is acquired.  Move the holder specific code in
inode_go_instantiate() over to inode_go_held().
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glock.c

@@ -488,7 +488,7 @@ int gfs2_instantiate(struct gfs2_holder *gh)
 
 again:
 	if (!test_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags))
-		return 0;
+		goto done;
 
 	/*
 	 * Since we unlock the lockref lock, we set a flag to indicate
@@ -511,7 +511,13 @@ int gfs2_instantiate(struct gfs2_holder *gh)
 	if (!ret)
 		clear_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
 	clear_and_wake_up_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
-	return ret;
+	if (ret)
+		return ret;
+
+done:
+	if (glops->go_held)
+		return glops->go_held(gh);
+	return 0;
 }
 
 /**

fs/gfs2/glops.c

@@ -489,14 +489,21 @@ static int inode_go_instantiate(struct gfs2_holder *gh)
 {
 	struct gfs2_glock *gl = gh->gh_gl;
 	struct gfs2_inode *ip = gl->gl_object;
-	int error = 0;
 
 	if (!ip) /* no inode to populate - read it in later */
-		goto out;
+		return 0;
 
-	error = gfs2_inode_refresh(ip);
-	if (error)
-		goto out;
+	return gfs2_inode_refresh(ip);
+}
+
+static int inode_go_held(struct gfs2_holder *gh)
+{
+	struct gfs2_glock *gl = gh->gh_gl;
+	struct gfs2_inode *ip = gl->gl_object;
+	int error = 0;
+
+	if (!ip) /* no inode to populate - read it in later */
+		return 0;
 
 	if (gh->gh_state != LM_ST_DEFERRED)
 		inode_dio_wait(&ip->i_inode);
@@ -506,7 +513,6 @@ static int inode_go_instantiate(struct gfs2_holder *gh)
 	    (gh->gh_state == LM_ST_EXCLUSIVE))
 		error = gfs2_truncatei_resume(ip);
 
-out:
 	return error;
 }
 
@@ -730,6 +736,7 @@ const struct gfs2_glock_operations gfs2_inode_glops = {
 	.go_inval = inode_go_inval,
 	.go_demote_ok = inode_go_demote_ok,
 	.go_instantiate = inode_go_instantiate,
+	.go_held = inode_go_held,
 	.go_dump = inode_go_dump,
 	.go_type = LM_TYPE_INODE,
 	.go_flags = GLOF_ASPACE | GLOF_LRU | GLOF_LVB,

fs/gfs2/incore.h

@@ -220,6 +220,7 @@ struct gfs2_glock_operations {
 	void (*go_inval) (struct gfs2_glock *gl, int flags);
 	int (*go_demote_ok) (const struct gfs2_glock *gl);
 	int (*go_instantiate) (struct gfs2_holder *gh);
+	int (*go_held)(struct gfs2_holder *gh);
 	void (*go_dump)(struct seq_file *seq, struct gfs2_glock *gl,
 			const char *fs_id_buf);
 	void (*go_callback)(struct gfs2_glock *gl, bool remote);