[Yaffs] Rewind readdir when entries deleted

[Charles Manning]

On Saturday 05 November 2005 13:34, Todd Poynor wrote:
> busybox rm -rf <dir>, bonnie++, and other applications that do not
> rewinddir after each file removal, may fail to remove all files when
> multiple readdir calls are needed due to the number of dentries.  The
> file position passed into the subsequent readdir calls no longer
> describes the list position of the "next" entry to be returned.
>
> The below solution causes a subsequent readdir to restart whenever a
> file is deleted from that directory since the previous call.  In some
> uses this will cause dentries to be returned twice, but it is a quick
> solution for rm -rf.  If the inode version bumping introduced below
> remains the sole situation in which a version would be bumped by yaffs,
> it would be possible to compute the proper index to restart at.
>
> Other suggestions welcomed.  Note some shells introduce a rewinddir into
> the rm -r code to avoid this problem.

It might instead make sense to use the feature introduced in 1.19 to handle 
this a bit faster in yaffs direct. See
http://www.aleph1.co.uk/cgi-bin/viewcvs.cgi/yaffs2/yaffs_guts.c?r1=1.18&r2=1.19
This implements a fix for the problem

I first encountered a problem like this when using YAFFS in WinCE. The problem 
was addressed by creating a list of returned objects and checking the list 
before returning it. This solution degrades with large directories and the 
above solution handles it.

Perhaps it makes sense to propagate this solution into Linux space too.

>
> Signed-off-by: Todd Poynor <tpoynor at mvista.com>
>
> Index: yaffs_fs.c
> ===================================================================
> RCS file: /home/aleph1/cvs/yaffs2/yaffs_fs.c,v
> retrieving revision 1.33
> diff -u -r1.33 yaffs_fs.c
> --- yaffs_fs.c	27 Oct 2005 22:24:04 -0000	1.33
> +++ yaffs_fs.c	5 Nov 2005 00:28:27 -0000
> @@ -814,6 +814,15 @@
>
>  	curoffs = 1;
>
> +	/* If the directory has changed since the open or last call to
> +	   readdir, rewind to after the 2 canned entries. */
> +
> +	if (f->f_version != inode->i_version) {
> +		offset = 2;
> +		f->f_pos = offset;
> +		f->f_version = inode->i_version;
> +	}
> +
>  	list_for_each(i, &obj->variant.directoryVariant.children) {
>  		curoffs++;
>  		if (curoffs >= offset) {
> @@ -981,15 +990,15 @@
>
>  	retVal = yaffs_Unlink(yaffs_InodeToObject(dir), dentry->d_name.name);
>
> -	yaffs_GrossUnlock(dev);
> -
>  	if (retVal == YAFFS_OK) {
>  		dentry->d_inode->i_nlink--;
> +		dir->i_version++;
> +		yaffs_GrossUnlock(dev);
>  		mark_inode_dirty(dentry->d_inode);
>  		return 0;
> -	} else {
> -		return -ENOTEMPTY;
>  	}
> +	yaffs_GrossUnlock(dev);
> +	return -ENOTEMPTY;
>  }
>
>  /*
>
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