gfs2: fix scheduling while atomic bug in glocks

Before this patch, in the unlikely event that gfs2_glock_dq encountered
a withdraw, it would do a wait_on_bit to wait for its journal to be
recovered, but it never released the glock's spin_lock, which caused a
scheduling-while-atomic error.

This patch unlocks the lockref spin_lock before waiting for recovery.

Fixes: 601ef0d52e96 ("gfs2: Force withdraw to replay journals and wait for it to finish")
Cc: stable@vger.kernel.org # v5.7+
Reported-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index ea7fc5c..8c547db 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1466,9 +1466,11 @@ void gfs2_glock_dq(struct gfs2_holder *gh)
            glock_blocked_by_withdraw(gl) &&
            gh->gh_gl != sdp->sd_jinode_gl) {
                sdp->sd_glock_dqs_held++;
+               spin_unlock(&gl->gl_lockref.lock);
                might_sleep();
                wait_on_bit(&sdp->sd_flags, SDF_WITHDRAW_RECOVERY,
                            TASK_UNINTERRUPTIBLE);
+               spin_lock(&gl->gl_lockref.lock);
        }
        if (gh->gh_flags & GL_NOCACHE)
                handle_callback(gl, LM_ST_UNLOCKED, 0, false);