[Cluster-devel] [GFS2] Fix glock dumping oops

[Steven Whitehouse]

Hi,

On Tue, 2007-07-24 at 08:24 -0500, Kevin Anderson wrote:
> What bugzilla does this address?
> 
> Kevin
> 

bz #248479, GFS2: cat /debug/gfs2/morph-cluster:gfs_vs0/glocks, panic!

Steve.

> On Tue, 2007-07-24 at 14:11 +0100, Steven Whitehouse wrote: 
> > Hi,
> > 
> > This fixes an oops which was occurring during glock dumping due to the
> > seq file code not taking a reference to the glock. Also this fixes a
> > memory leak which occurred in certain cases, in turn preventing the
> > filesystem from unmounting.
> > 
> > Steve.
> > 
> > ----------------------------------------------------------------------
> > diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> > index d403fd7..e4bc8ae 100644
> > --- a/fs/gfs2/glock.c
> > +++ b/fs/gfs2/glock.c
> > @@ -46,7 +46,6 @@ struct glock_iter {
> >  	int hash;                     /* hash bucket index         */
> >  	struct gfs2_sbd *sdp;         /* incore superblock         */
> >  	struct gfs2_glock *gl;        /* current glock struct      */
> > -	struct hlist_head *hb_list;   /* current hash bucket ptr   */
> >  	struct seq_file *seq;         /* sequence file for debugfs */
> >  	char string[512];             /* scratch space             */
> >  };
> > @@ -1990,47 +1989,38 @@ int __init gfs2_glock_init(void)
> >  
> >  static int gfs2_glock_iter_next(struct glock_iter *gi)
> >  {
> > +	struct gfs2_glock *gl;
> > +
> >  	read_lock(gl_lock_addr(gi->hash));
> > -	while (1) {
> > -		if (!gi->hb_list) {  /* If we don't have a hash bucket yet */
> > -			gi->hb_list = &gl_hash_table[gi->hash].hb_list;
> > -			if (hlist_empty(gi->hb_list)) {
> > -				read_unlock(gl_lock_addr(gi->hash));
> > -				gi->hash++;
> > -				read_lock(gl_lock_addr(gi->hash));
> > -				gi->hb_list = NULL;
> > -				if (gi->hash >= GFS2_GL_HASH_SIZE) {
> > -					read_unlock(gl_lock_addr(gi->hash));
> > -					return 1;
> > -				}
> > -				else
> > -					continue;
> > -			}
> > -			if (!hlist_empty(gi->hb_list)) {
> > -				gi->gl = list_entry(gi->hb_list->first,
> > -						    struct gfs2_glock,
> > -						    gl_list);
> > -			}
> > -		} else {
> > -			if (gi->gl->gl_list.next == NULL) {
> > -				read_unlock(gl_lock_addr(gi->hash));
> > -				gi->hash++;
> > -				read_lock(gl_lock_addr(gi->hash));
> > -				gi->hb_list = NULL;
> > -				continue;
> > -			}
> > -			gi->gl = list_entry(gi->gl->gl_list.next,
> > -					    struct gfs2_glock, gl_list);
> > -		}
> > +	gl = gi->gl;
> > +	if (gl) {
> > +		gi->gl = hlist_entry(gl->gl_list.next, struct gfs2_glock,
> > +				     gl_list);
> >  		if (gi->gl)
> > -			break;
> > +			gfs2_glock_hold(gi->gl);
> >  	}
> >  	read_unlock(gl_lock_addr(gi->hash));
> > +	if (gl)
> > +		gfs2_glock_put(gl);
> > +
> > +	while(gi->gl == NULL) {
> > +		gi->hash++;
> > +		if (gi->hash >= GFS2_GL_HASH_SIZE)
> > +			return 1;
> > +		read_lock(gl_lock_addr(gi->hash));
> > +		gi->gl = hlist_entry(gl_hash_table[gi->hash].hb_list.first,
> > +				     struct gfs2_glock, gl_list);
> > +		if (gi->gl)
> > +			gfs2_glock_hold(gi->gl);
> > +		read_unlock(gl_lock_addr(gi->hash));
> > +	}
> >  	return 0;
> >  }
> >  
> >  static void gfs2_glock_iter_free(struct glock_iter *gi)
> >  {
> > +	if (gi->gl)
> > +		gfs2_glock_put(gi->gl);
> >  	kfree(gi);
> >  }
> >  
> > @@ -2044,12 +2034,17 @@ static struct glock_iter *gfs2_glock_iter_init(struct gfs2_sbd *sdp)
> >  
> >  	gi->sdp = sdp;
> >  	gi->hash = 0;
> > -	gi->gl = NULL;
> > -	gi->hb_list = NULL;
> >  	gi->seq = NULL;
> >  	memset(gi->string, 0, sizeof(gi->string));
> >  
> > -	if (gfs2_glock_iter_next(gi)) {
> > +	read_lock(gl_lock_addr(gi->hash));
> > +	gi->gl = hlist_entry(gl_hash_table[gi->hash].hb_list.first,
> > +			     struct gfs2_glock, gl_list);
> > +	if (gi->gl)
> > +		gfs2_glock_hold(gi->gl);
> > +	read_unlock(gl_lock_addr(gi->hash));
> > +
> > +	if (!gi->gl && gfs2_glock_iter_next(gi)) {
> >  		gfs2_glock_iter_free(gi);
> >  		return NULL;
> >  	}
> > @@ -2066,7 +2061,7 @@ static void *gfs2_glock_seq_start(struct seq_file *file, loff_t *pos)
> >  	if (!gi)
> >  		return NULL;
> >  
> > -	while (n--) {
> > +	while(n--) {
> >  		if (gfs2_glock_iter_next(gi)) {
> >  			gfs2_glock_iter_free(gi);
> >  			return NULL;
> > @@ -2093,7 +2088,9 @@ static void *gfs2_glock_seq_next(struct seq_file *file, void *iter_ptr,
> >  
> >  static void gfs2_glock_seq_stop(struct seq_file *file, void *iter_ptr)
> >  {
> > -	/* nothing for now */
> > +	struct glock_iter *gi = iter_ptr;
> > +	if (gi)
> > +		gfs2_glock_iter_free(gi);
> >  }
> >  
> >  static int gfs2_glock_seq_show(struct seq_file *file, void *iter_ptr)
> > 
> >