Re: [BUG] Reiserfs panic while running fsstress due to multipletruncate "safe links" for a file.

[Andrew Morton]

On Mon, 27 Nov 2006 15:37:49 -0800
Suzuki <suzuki@xxxxxxxxxx> wrote:

> * Do not add save links for O_DIRECT writes.  
> 
> We add a save link for O_DIRECT writes to protect the i_size against the crashes before we actually finish the I/O. If we hit an -ENOSPC in aops->prepare_write(), we would do a truncate() to release the blocks which might have got initialized. Now the truncate would add another save link for the same inode causing a reiserfs panic for having multiple save links for the same inode.
> 
> 

OK...

But how does this patch fix it?  It removes a lot of code - how come we
don't need it any more?

> 
> 
> Index: linux-2.6.19-rc1/fs/reiserfs/file.c
> ===================================================================
> --- linux-2.6.19-rc1.orig/fs/reiserfs/file.c	2006-10-10 05:54:30.000000000 -0700
> +++ linux-2.6.19-rc1/fs/reiserfs/file.c	2006-11-21 17:17:36.000000000 -0800
> @@ -1306,56 +1306,8 @@
>  			count = MAX_NON_LFS - (unsigned long)*ppos;
>  	}
>  
> -	if (file->f_flags & O_DIRECT) {	// Direct IO needs treatment
> -		ssize_t result, after_file_end = 0;
> -		if ((*ppos + count >= inode->i_size)
> -		    || (file->f_flags & O_APPEND)) {
> -			/* If we are appending a file, we need to put this savelink in here.
> -			   If we will crash while doing direct io, finish_unfinished will
> -			   cut the garbage from the file end. */
> -			reiserfs_write_lock(inode->i_sb);
> -			err =
> -			    journal_begin(&th, inode->i_sb,
> -					  JOURNAL_PER_BALANCE_CNT);
> -			if (err) {
> -				reiserfs_write_unlock(inode->i_sb);
> -				return err;
> -			}
> -			reiserfs_update_inode_transaction(inode);
> -			add_save_link(&th, inode, 1 /* Truncate */ );
> -			after_file_end = 1;
> -			err =
> -			    journal_end(&th, inode->i_sb,
> -					JOURNAL_PER_BALANCE_CNT);
> -			reiserfs_write_unlock(inode->i_sb);
> -			if (err)
> -				return err;
> -		}
> -		result = do_sync_write(file, buf, count, ppos);
> -
> -		if (after_file_end) {	/* Now update i_size and remove the savelink */
> -			struct reiserfs_transaction_handle th;
> -			reiserfs_write_lock(inode->i_sb);
> -			err = journal_begin(&th, inode->i_sb, 1);
> -			if (err) {
> -				reiserfs_write_unlock(inode->i_sb);
> -				return err;
> -			}
> -			reiserfs_update_inode_transaction(inode);
> -			mark_inode_dirty(inode);
> -			err = journal_end(&th, inode->i_sb, 1);
> -			if (err) {
> -				reiserfs_write_unlock(inode->i_sb);
> -				return err;
> -			}
> -			err = remove_save_link(inode, 1 /* truncate */ );
> -			reiserfs_write_unlock(inode->i_sb);
> -			if (err)
> -				return err;
> -		}
> -
> -		return result;
> -	}
> +	if (file->f_flags & O_DIRECT) 
> +		return do_sync_write(file, buf, count, ppos);
>  
>  	if (unlikely((ssize_t) count < 0))
>  		return -EINVAL;
-
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