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Message-ID: <ZE6a310qzNzd40l5@mit.edu> Date: Sun, 30 Apr 2023 12:44:15 -0400 From: "Theodore Ts'o" <tytso@....edu> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org, Christian Brauner <brauner@...nel.org>, syzbot+aacb82fca60873422114@...kaller.appspotmail.com, syzbot+6b7df7d5506b32467149@...kaller.appspotmail.com, syzkaller-bugs@...glegroups.com Subject: Re: [PATCH] ext4: Fix lockdep warning when enabling MMP On Sun, Apr 30, 2023 at 12:34:00PM -0400, Theodore Ts'o wrote: > On Tue, Apr 11, 2023 at 02:10:19PM +0200, Jan Kara wrote: > > 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(). > > > > Reported-by: syzbot+aacb82fca60873422114@...kaller.appspotmail.com > > I believe this is the wrong Reported-by. The correct one looks like > it should be: ... By the way, I noticed because I was browsing the syzbot dashboard for the ext4 subsystem, and the Syzbot page for "possible deadlock in sys_quotactl_fd"[1], I saw a discussion link to lore for the patch "[PATCH] ext4: Fix lockdep warning when enabling MMP", and said, "Hmm.... that looks wrong." :-) [1] https://syzkaller.appspot.com/bug?id=1680b22e0e5eb9245a6faff10221ed76b8c5eb81 Anyway, thanks to the Syzbot team for adding Disscusion links to the Syzbot pages. It makes it a lot easier to find discussions related to a particular issue. Note: you can also manually add a thread to the discussions section by simply adding a CC to the Reported-by link for the particular issue (for example, "Cc: syzbot+aacb82fca60873422114@...kaller.appspotmail.com"). Cheers, - Ted
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