Re: [syzbot] Re: [syzbot] [ocfs2?] kernel BUG in ocfs2_iget

[syzbot <syzbot+5bdd4953bc58c8fbd6eb@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: Re: [syzbot] [ocfs2?] kernel BUG in ocfs2_iget
Author: lizhi.xu@windriver.com

BH_Lock state check micro buffer_locked not work?

#syz test: upstream d07b43284ab3

diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
index cdb9b9bdea1f..f67f82adfee2 100644
--- a/fs/ocfs2/buffer_head_io.c
+++ b/fs/ocfs2/buffer_head_io.c
@@ -148,6 +148,8 @@ int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
 		get_bh(bh); /* for end_buffer_read_sync() */
 		bh->b_end_io = end_buffer_read_sync;
 		submit_bh(REQ_OP_READ, bh);
+		printk("bio, jbd: %d, dirty: %d, i: %d, bh: %p, buflocked: %d, bfl: %d, status: %d, %s\n", buffer_jbd(bh),
+			buffer_dirty(bh), i, bh, buffer_locked(bh), bh->b_state & BH_Lock, status, __func__);
 	}
 
 read_failure:
@@ -170,9 +172,15 @@ int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
 			continue;
 		}
 
+		printk("rf, jbd: %d, dirty: %d, i: %d, bh: %p, buflocked: %d, bfl: %d, status: %d, %s\n", buffer_jbd(bh),
+			buffer_dirty(bh), i, bh, buffer_locked(bh), bh->b_state & BH_Lock, status, __func__);
 		/* No need to wait on the buffer if it's managed by JBD. */
-		if (!buffer_jbd(bh))
+		if (!buffer_jbd(bh)) {
+			if (!buffer_locked(bh) && (bh->b_state & BH_Lock) && bh->b_end_io == end_buffer_read_sync)
+				lock_buffer(bh);
+
 			wait_on_buffer(bh);
+		}
 
 		if (!buffer_uptodate(bh)) {
 			/* Status won't be cleared from here on out,
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index e022e40b099e..33c179fa522e 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -411,7 +411,7 @@ map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 static inline void wait_on_buffer(struct buffer_head *bh)
 {
 	might_sleep();
-	if (buffer_locked(bh))
+	if (bh->b_state & BH_Lock)
 		__wait_on_buffer(bh);
 }