Commit 074d7306 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Silence "suspicious RCU usage in gfs2_permission" warning 



Commit 0abd1557 added rcu_dereference() for dereferencing ip->i_gl
in gfs2_permission.  This now causes lockdep to complain when
gfs2_permission is called in non-RCU context:

    WARNING: suspicious RCU usage in gfs2_permission

Switch to rcu_dereference_check() and check for the MAY_NOT_BLOCK flag
to shut up lockdep when we know that dereferencing ip->i_gl is safe.

Fixes: 0abd1557 ("gfs2: fix an oops in gfs2_permission")
Reported-by: default avatar <syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent d6fc6c93

fs/gfs2/inode.c

+4 −3
Original line number Diff line number Diff line
@@ -1867,6 +1867,7 @@ static const char *gfs2_get_link(struct dentry *dentry, 
int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,

		    int mask)

{

	int may_not_block = mask & MAY_NOT_BLOCK;

	struct gfs2_inode *ip;

	struct gfs2_holder i_gh;

	struct gfs2_glock *gl;
@@ -1874,14 +1875,14 @@ int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode, 


	gfs2_holder_mark_uninitialized(&i_gh);

	ip = GFS2_I(inode);

	gl = rcu_dereference(ip->i_gl);

	gl = rcu_dereference_check(ip->i_gl, !may_not_block);

	if (unlikely(!gl)) {

		/* inode is getting torn down, must be RCU mode */

		WARN_ON_ONCE(!(mask & MAY_NOT_BLOCK));

		WARN_ON_ONCE(!may_not_block);

		return -ECHILD;

        }

	if (gfs2_glock_is_locked_by_me(gl) == NULL) {

		if (mask & MAY_NOT_BLOCK)

		if (may_not_block)

			return -ECHILD;

		error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);

		if (error)