From: Andreas Gruenbacher <agruenba@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
gfs2@lists.linux.dev, syzkaller-bugs@googlegroups.com,
syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com
Subject: [PATCH] gfs2: Silence "suspicious RCU usage in gfs2_permission" warning
Date: Mon, 30 Oct 2023 22:33:31 +0100 [thread overview]
Message-ID: <20231030213332.793030-1-agruenba@redhat.com> (raw)
Commit 0abd1557e21c 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: 0abd1557e21c ("gfs2: fix an oops in gfs2_permission")
Reported-by: syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 79e96130ef9e..425bf4e90448 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -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)
reply other threads:[~2023-10-30 21:33 UTC|newest]
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