Re: ReiserFS / 2.4.6 / Data Corruption

[Hans Reiser <reiser@namesys.com>]

Andrew, can you do this such that there is no disruption of our disk format, and make a mount option
out of it, and probably we should use this patch....

After you make a mount option out of it, grev will benchmark it for us using the usual suite of
benchmarks.

Comments Chris?  

Thanks,

Hans

Andrew Morton wrote:
> 
> Joshua Schmidlkofer wrote:
> >
> > I've almost quit using reiser, because everytime I have a power outage, the
> > last 2 or three files that I've editted, even ones that I haven't touched in
> > a while, will usually be hopelessly corrupted.  The '<file>~' that Emacs
> > makes is usually fine though.
> 
> It's a matter of timing.  There is a lengthy window where the metadata
> is written, but its data is not.  If you crash in this window, the files
> contain old data.
> 
> You can narrow the window of exposure by fiddling with the
> parameters in /proc/sys/vm/bdflush - force a full flush every
> five seconds, say.
> 
> >   It seems to be that any open file is
> > in danger.  I don't know if this is normal, or not, but I switched to XFS on
> > several machines.  I have nothing against reiser.  I assumed that these
> > problems were due to immaturity....
> 
> I'm under the impression that XFS also leaves data in the hands
> of the kernel's normal writeback mechanisms and will thus be
> exposed to the same problem.  I may be wrong about this.
> 
> Here's a ten-minute hack which gives reiserfs a simple `ordered data'
> mode.  It simply pushes all the dirty buffers and pages out to disk
> before running a commit.  Performance is still OK.
> 
> I hit reset partway through a massive file tree copy and every
> file which had been copied came up peachy - which is very different
> from the behaviour without the patch.  Interestingly, there were
> zero truncated files as well.  hmmm...
> 
> --- linux-2.4.7/include/linux/fs.h      Sat Jul 21 12:37:14 2001
> +++ lk-ext3/include/linux/fs.h  Sat Jul 28 02:37:43 2001
> @@ -1061,6 +1061,7 @@ extern int fs_may_remount_ro(struct supe
>  extern int try_to_free_buffers(struct page *, unsigned int);
>  extern void refile_buffer(struct buffer_head * buf);
>  extern void end_buffer_io_sync(struct buffer_head *bh, int uptodate);
> +extern int flush_all_but_supers(kdev_t dev);
> 
>  /* reiserfs_writepage needs this */
>  extern void set_buffer_async_io(struct buffer_head *bh) ;
> --- linux-2.4.7/include/linux/reiserfs_fs_sb.h  Sat Jul 21 12:37:14 2001
> +++ lk-ext3/include/linux/reiserfs_fs_sb.h      Sat Jul 28 02:37:43 2001
> @@ -289,6 +289,8 @@ struct reiserfs_sb_info
>                                 /* To be obsoleted soon by per buffer seals.. -Hans */
>      atomic_t s_generation_counter; // increased by one every time the
>      // tree gets re-balanced
> +
> +    int no_sync;
> 
>      /* session statistics */
>      int s_kmallocs;
> --- linux-2.4.7/fs/reiserfs/journal.c   Sat Jul 21 12:37:14 2001
> +++ lk-ext3/fs/reiserfs/journal.c       Sat Jul 28 02:37:43 2001
> @@ -2719,6 +2719,9 @@ static int do_journal_end(struct reiserf
>    reiserfs_discard_all_prealloc(th); /* it should not involve new blocks into
>                                       * the transaction */
>  #endif
> +
> +  if (!p_s_sb->u.reiserfs_sb.no_sync)
> +       flush_all_but_supers(p_s_sb->s_dev);
> 
>    rs = SB_DISK_SUPER_BLOCK(p_s_sb) ;
>    /* setup description block */
> --- linux-2.4.7/fs/reiserfs/super.c     Wed Jul  4 18:21:31 2001
> +++ lk-ext3/fs/reiserfs/super.c Sat Jul 28 02:37:43 2001
> @@ -116,7 +116,9 @@ void reiserfs_put_super (struct super_bl
>    /* note, journal_release checks for readonly mount, and can decide not
>    ** to do a journal_end
>    */
> +  s->u.reiserfs_sb.no_sync = 1;
>    journal_release(&th, s) ;
> +  s->u.reiserfs_sb.no_sync = 0;
> 
>    for (i = 0; i < SB_BMAP_NR (s); i ++)
>      brelse (SB_AP_BITMAP (s)[i]);
> --- linux-2.4.7/fs/buffer.c     Sat Jul 21 12:37:14 2001
> +++ lk-ext3/fs/buffer.c Sat Jul 28 02:37:43 2001
> @@ -333,6 +333,18 @@ int fsync_dev(kdev_t dev)
>         return sync_buffers(dev, 1);
>  }
> 
> +int flush_all_but_supers(kdev_t dev)
> +{
> +       sync_buffers(dev, 0);
> +
> +       lock_kernel();
> +       sync_inodes(dev);
> +       DQUOT_SYNC(dev);
> +       unlock_kernel();
> +
> +       return sync_buffers(dev, 1);
> +}
> +
>  /*
>   * There's no real reason to pretend we should
>   * ever do anything differently
> --- linux-2.4.7/kernel/ksyms.c  Sat Jul 21 12:37:14 2001
> +++ lk-ext3/kernel/ksyms.c      Sat Jul 28 02:37:43 2001
> @@ -161,6 +161,7 @@ EXPORT_SYMBOL(d_lookup);
>  EXPORT_SYMBOL(__d_path);
>  EXPORT_SYMBOL(mark_buffer_dirty);
>  EXPORT_SYMBOL(set_buffer_async_io); /* for reiserfs_writepage */
> +EXPORT_SYMBOL(flush_all_but_supers);
>  EXPORT_SYMBOL(__mark_buffer_dirty);
>  EXPORT_SYMBOL(__mark_inode_dirty);
>  EXPORT_SYMBOL(get_empty_filp);