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Re: [xfs] Calltrace in 2.6.27 kernel]

To: "aluno3@xxxxxxxxxxxxxx" <aluno3@xxxxxxxxxxxxxx>
Subject: Re: [xfs] Calltrace in 2.6.27 kernel]
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 14 Nov 2008 11:30:56 -0500
Cc: hch@xxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <491D3BAB.2090207@xxxxxxxxxxxxxx>
References: <491C9687.6040305@xxxxxxxxxxxxxx> <491D3BAB.2090207@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Fri, Nov 14, 2008 at 09:49:47AM +0100, aluno3@xxxxxxxxxxxxxx wrote:
> Hi
> 
> I ran addr2line for both vmlinux and for first call trace (2.6.27)
> add2line returned:
> 
> addr2line -e ./vmlinux c029553d
> fs/xfs/xfs_log.c:3528
> 
> in source:
> 
>         /*
>          * If this happens during log recovery, don't worry about
>          * locking; the log isn't open for business yet.
>          */
>         if (!log ||
>             log->l_flags & XLOG_ACTIVE_RECOVERY) {
>                 mp->m_flags |= XFS_MOUNT_FS_SHUTDOWN;
>                 XFS_BUF_DONE(mp->m_sb_bp);                            
> //3528 line

Thanks a lot.  I think I figured out what happens:

 - we fail the buffer read in xlog_recover_do_inode_trans, and thus
   abort the mount.
 - but before that log recovery has started delayed writeback of inode
   buffers
 - during the mount error handling we call xfs_freesb, which NULLs
   mp->m_sb_bp after the inode has been unmounted
 - but the device close tries to flush all delayed buffers after that,
   and the inode buffer triggers the filesystem shutdown case because
   it also had an I/O error.
 - Now we try to mark the superblock buffer done, but it's not there
   anymore.

The easy fix is to just check for a NULL mp->m_sb_bp before marking it
done.  Note that this will only fix the XFS oops, but not the underling
DM issue, for which I'd ask on the device mapper list.


Index: xfs-2.6/fs/xfs/xfs_log.c
===================================================================
--- xfs-2.6.orig/fs/xfs/xfs_log.c       2008-11-14 17:28:55.000000000 +0100
+++ xfs-2.6/fs/xfs/xfs_log.c    2008-11-14 17:29:20.000000000 +0100
@@ -3525,7 +3525,8 @@ xfs_log_force_umount(
        if (!log ||
            log->l_flags & XLOG_ACTIVE_RECOVERY) {
                mp->m_flags |= XFS_MOUNT_FS_SHUTDOWN;
-               XFS_BUF_DONE(mp->m_sb_bp);
+               if (mp->m_sb_bp)
+                       XFS_BUF_DONE(mp->m_sb_bp);
                return 0;
        }
 
@@ -3546,7 +3547,8 @@ xfs_log_force_umount(
        spin_lock(&log->l_icloglock);
        spin_lock(&log->l_grant_lock);
        mp->m_flags |= XFS_MOUNT_FS_SHUTDOWN;
-       XFS_BUF_DONE(mp->m_sb_bp);
+       if (mp->m_sb_bp)
+               XFS_BUF_DONE(mp->m_sb_bp);
        /*
         * This flag is sort of redundant because of the mount flag, but
         * it's good to maintain the separation between the log and the rest

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