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gfs2: Silence "suspicious RCU usage in gfs2_permission" warning

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Commit 0abd1557e2 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: 0abd1557e2 ("gfs2: fix an oops in gfs2_permission")
Reported-by: syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2023-10-30 22:06:05 +01:00
parent d6fc6c9363
commit 074d7306a4
1 changed files with 4 additions and 3 deletions
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7
fs/gfs2/inode.c
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@ -1867,6 +1867,7 @@ out:
int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode, int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,
int mask) int mask)
{ {
int may_not_block = mask & MAY_NOT_BLOCK;
struct gfs2_inode *ip; struct gfs2_inode *ip;
struct gfs2_holder i_gh; struct gfs2_holder i_gh;
struct gfs2_glock *gl; struct gfs2_glock *gl;
@ -1874,14 +1875,14 @@ int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,
gfs2_holder_mark_uninitialized(&i_gh); gfs2_holder_mark_uninitialized(&i_gh);
ip = GFS2_I(inode); ip = GFS2_I(inode);
gl = rcu_dereference(ip->i_gl); gl = rcu_dereference_check(ip->i_gl, !may_not_block);
if (unlikely(!gl)) { if (unlikely(!gl)) {
/* inode is getting torn down, must be RCU mode */ /* inode is getting torn down, must be RCU mode */
WARN_ON_ONCE(!(mask & MAY_NOT_BLOCK)); WARN_ON_ONCE(!may_not_block);
return -ECHILD; return -ECHILD;
} }
if (gfs2_glock_is_locked_by_me(gl) == NULL) { if (gfs2_glock_is_locked_by_me(gl) == NULL) {
if (mask & MAY_NOT_BLOCK) if (may_not_block)
return -ECHILD; return -ECHILD;
error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh); error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
if (error) if (error)