Patch "gfs2: Fix glock_hash_walk bugs" has been added to the 5.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    gfs2: Fix glock_hash_walk bugs

to the 5.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gfs2-fix-glock_hash_walk-bugs.patch
and it can be found in the queue-5.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 814f88e8de67bec7913c613e02101b534c396147
Author: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Date:   Thu Oct 7 15:57:44 2021 +0200

    gfs2: Fix glock_hash_walk bugs
    
    [ Upstream commit 7427f3bb49d81525b7dd1d0f7c5f6bbc752e6f0e ]
    
    So far, glock_hash_walk took a reference on each glock it iterated over, and it
    was the examiner's responsibility to drop those references.  Dropping the final
    reference to a glock can sleep and the examiners are called in a RCU critical
    section with spin locks held, so examiners that didn't need the extra reference
    had to drop it asynchronously via gfs2_glock_queue_put or similar.  This wasn't
    done correctly in thaw_glock which did call gfs2_glock_put, and not at all in
    dump_glock_func.
    
    Change glock_hash_walk to not take glock references at all.  That way, the
    examiners that don't need them won't have to bother with slow asynchronous
    puts, and the examiners that do need references can take them themselves.
    
    Reported-by: Alexander Aring <aahringo@xxxxxxxxxx>
    Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index fea68ed127b89..b17b6350c0317 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1894,10 +1894,10 @@ static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
 	do {
 		rhashtable_walk_start(&iter);
 
-		while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl))
-			if (gl->gl_name.ln_sbd == sdp &&
-			    lockref_get_not_dead(&gl->gl_lockref))
+		while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl)) {
+			if (gl->gl_name.ln_sbd == sdp)
 				examiner(gl);
+		}
 
 		rhashtable_walk_stop(&iter);
 	} while (cond_resched(), gl == ERR_PTR(-EAGAIN));
@@ -1939,7 +1939,6 @@ static void flush_delete_work(struct gfs2_glock *gl)
 					   &gl->gl_delete, 0);
 		}
 	}
-	gfs2_glock_queue_work(gl, 0);
 }
 
 void gfs2_flush_delete_work(struct gfs2_sbd *sdp)
@@ -1956,10 +1955,10 @@ void gfs2_flush_delete_work(struct gfs2_sbd *sdp)
 
 static void thaw_glock(struct gfs2_glock *gl)
 {
-	if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) {
-		gfs2_glock_put(gl);
+	if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))
+		return;
+	if (!lockref_get_not_dead(&gl->gl_lockref))
 		return;
-	}
 	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
 	gfs2_glock_queue_work(gl, 0);
 }
@@ -1975,9 +1974,12 @@ static void clear_glock(struct gfs2_glock *gl)
 	gfs2_glock_remove_from_lru(gl);
 
 	spin_lock(&gl->gl_lockref.lock);
-	if (gl->gl_state != LM_ST_UNLOCKED)
-		handle_callback(gl, LM_ST_UNLOCKED, 0, false);
-	__gfs2_glock_queue_work(gl, 0);
+	if (!__lockref_is_dead(&gl->gl_lockref)) {
+		gl->gl_lockref.count++;
+		if (gl->gl_state != LM_ST_UNLOCKED)
+			handle_callback(gl, LM_ST_UNLOCKED, 0, false);
+		__gfs2_glock_queue_work(gl, 0);
+	}
 	spin_unlock(&gl->gl_lockref.lock);
 }