This is a note to let you know that I've just added the patch titled
ext4: fix lockdep warning when enabling MMP
to the 6.2-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:
ext4-fix-lockdep-warning-when-enabling-mmp.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 949f95ff39bf188e594e7ecd8e29b82eb108f5bf Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 11 Apr 2023 14:10:19 +0200
Subject: ext4: fix lockdep warning when enabling MMP
From: Jan Kara <jack@xxxxxxx>
commit 949f95ff39bf188e594e7ecd8e29b82eb108f5bf upstream.
When we enable MMP in ext4_multi_mount_protect() during mount or
remount, we end up calling sb_start_write() from write_mmp_block(). This
triggers lockdep warning because freeze protection ranks above s_umount
semaphore we are holding during mount / remount. The problem is harmless
because we are guaranteed the filesystem is not frozen during mount /
remount but still let's fix the warning by not grabbing freeze
protection from ext4_multi_mount_protect().
Cc: stable@xxxxxxxxxx
Reported-by: syzbot+6b7df7d5506b32467149@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=ab7e5b6f400b7778d46f01841422e5718fb81843
Signed-off-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230411121019.21940-1-jack@xxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/mmp.c | 30 +++++++++++++++++++++---------
1 file changed, 21 insertions(+), 9 deletions(-)
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -39,28 +39,36 @@ static void ext4_mmp_csum_set(struct sup
* Write the MMP block using REQ_SYNC to try to get the block on-disk
* faster.
*/
-static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
+static int write_mmp_block_thawed(struct super_block *sb,
+ struct buffer_head *bh)
{
struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
- /*
- * We protect against freezing so that we don't create dirty buffers
- * on frozen filesystem.
- */
- sb_start_write(sb);
ext4_mmp_csum_set(sb, mmp);
lock_buffer(bh);
bh->b_end_io = end_buffer_write_sync;
get_bh(bh);
submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh);
wait_on_buffer(bh);
- sb_end_write(sb);
if (unlikely(!buffer_uptodate(bh)))
return -EIO;
-
return 0;
}
+static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
+{
+ int err;
+
+ /*
+ * We protect against freezing so that we don't create dirty buffers
+ * on frozen filesystem.
+ */
+ sb_start_write(sb);
+ err = write_mmp_block_thawed(sb, bh);
+ sb_end_write(sb);
+ return err;
+}
+
/*
* Read the MMP block. It _must_ be read from disk and hence we clear the
* uptodate flag on the buffer.
@@ -340,7 +348,11 @@ skip:
seq = mmp_new_seq();
mmp->mmp_seq = cpu_to_le32(seq);
- retval = write_mmp_block(sb, bh);
+ /*
+ * On mount / remount we are protected against fs freezing (by s_umount
+ * semaphore) and grabbing freeze protection upsets lockdep
+ */
+ retval = write_mmp_block_thawed(sb, bh);
if (retval)
goto failed;
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-6.2/inotify-avoid-reporting-event-with-invalid-wd.patch
queue-6.2/ext4-fix-warning-in-mb_find_extent.patch
queue-6.2/ext4-avoid-deadlock-in-fs-reclaim-with-page-writeback.patch
queue-6.2/writeback-fix-call-of-incorrect-macro.patch
queue-6.2/ext4-check-iomap-type-only-if-ext4_iomap_begin-does-not-fail.patch
queue-6.2/ext4-fix-lockdep-warning-when-enabling-mmp.patch
queue-6.2/ext4-fix-data-races-when-using-cached-status-extents.patch
