linux-kernel - Forwarded: [PATCH] btrfs: debug folio_alloc

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Message-ID: <6960b720.050a0220.1c677c.03b9.GAE@google.com>
Date: Fri, 09 Jan 2026 00:06:56 -0800
From: syzbot <syzbot+b4a2af3000eaa84d95d5@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Forwarded: [PATCH] btrfs: debug folio_alloc_buffers parameters

For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com.

***

Subject: [PATCH] btrfs: debug folio_alloc_buffers parameters
Author: kartikey406@...il.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Debug patch to understand NULL pointer dereference in create_empty_buffers.
Print folio_size and blocksize to identify why folio_alloc_buffers returns NULL.

NOT FOR MERGE - debug only.

Signed-off-by: Deepanshu Kartikey <kartikey406@...il.com>
---
 fs/buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 838c0c571022..487a32faaa16 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -928,7 +928,7 @@ struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
 	/* The folio lock pins the memcg */
 	memcg = folio_memcg(folio);
 	old_memcg = set_active_memcg(memcg);
-
+	pr_err("DEBUG: folio_size=%lu blocksize=%lu\n",folio_size(folio), size);
 	head = NULL;
 	offset = folio_size(folio);
 	while ((offset -= size) >= 0) {
-- 
2.43.0