linux-kernel - [PATCH V3 0/2] JFS: Implement migrate_folio for jfs_metapage

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Message-ID: <20250417060630.197278-1-shivankg@amd.com>
Date: Thu, 17 Apr 2025 06:06:29 +0000
From: Shivank Garg <shivankg@....com>
To: <shaggy@...nel.org>, <akpm@...ux-foundation.org>
CC: <willy@...radead.org>, <shivankg@....com>, <david@...hat.com>,
	<wangkefeng.wang@...wei.com>, <jane.chu@...cle.com>, <ziy@...dia.com>,
	<donettom@...ux.ibm.com>, <apopple@...dia.com>,
	<jfs-discussion@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>, <syzbot+8bb6fd945af4e0ad9299@...kaller.appspotmail.com>
Subject: [PATCH V3 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

This patch addresses a warning that occurs during memory compaction due
to JFS's missing migrate_folio operation. The warning was introduced by
commit 7ee3647 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystem don't implement migrate_folio.

The syzbot reported following [1]:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
  Modules linked in:
  CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
  RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
  RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

This Implement metapage_migrate_folio which handles both single and multiple
metapages per page configurations.

[1]: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299

V1/V2:
https://lore.kernel.org/all/20250413172356.561544-1-shivankg@amd.com

#syz test: https://github.com/AMDESE/linux-mm.git 07246f14ea

Best Regards,
Shivank

Shivank Garg (2):
  mm: export folio_expected_refs for JFS migration handler
  jfs: implement migrate_folio for jfs_metapage_aops

 fs/jfs/jfs_metapage.c   | 94 +++++++++++++++++++++++++++++++++++++++++
 include/linux/migrate.h |  1 +
 mm/migrate.c            |  3 +-
 3 files changed, 97 insertions(+), 1 deletion(-)

-- 
2.34.1