Re: [patch] cifs: don't overwrite dentry name in d_revalidate

[Jeff Layton <jlayton@redhat.com>]

On Thu, 11 Nov 2010 18:42:16 +1100
Nick Piggin <npiggin@kernel.dk> wrote:

> Instead, use fatfs's method for dealing with negative dentries to
> preserve case, rather than overwrite dentry name in d_revalidate, which
> is a bit ugly and also gets in the way of doing lock-free path walking.
> 
> Signed-off-by: Nick Piggin <npiggin@kernel.dk>
> 
> Index: linux-2.6/fs/cifs/dir.c
> ===================================================================
> --- linux-2.6.orig/fs/cifs/dir.c	2010-11-11 18:05:55.000000000 +1100
> +++ linux-2.6/fs/cifs/dir.c	2010-11-11 18:06:49.000000000 +1100
> @@ -656,22 +656,34 @@ cifs_lookup(struct inode *parent_dir_ino
>  static int
>  cifs_d_revalidate(struct dentry *direntry, struct nameidata *nd)
>  {
> -	int isValid = 1;
> -
>  	if (direntry->d_inode) {
>  		if (cifs_revalidate_dentry(direntry))
>  			return 0;
> -	} else {
> -		cFYI(1, "neg dentry 0x%p name = %s",
> -			 direntry, direntry->d_name.name);
> -		if (time_after(jiffies, direntry->d_time + HZ) ||
> -			!lookupCacheEnabled) {
> -			d_drop(direntry);
> -			isValid = 0;
> -		}
> +		else
> +			return 1;
> +	}
> +
> +	/*
> +	 * This may be nfsd (or something), anyway, we can't see the
> +	 * intent of this. So, since this can be for creation, drop it.
> +	 */
> +	if (!nd)
> +		return 0;
> +
> +	/*
> +	 * Drop the negative dentry, in order to make sure to use the
> +	 * case sensitive name which is specified by user if this is
> +	 * for creation.
> +	 */
> +	if (!(nd->flags & (LOOKUP_CONTINUE | LOOKUP_PARENT))) {
> +		if (nd->flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
> +			return 0;
>  	}
>  
> -	return isValid;
> +	if (time_after(jiffies, direntry->d_time + HZ) || !lookupCacheEnabled)
> +		return 0;
> +
> +	return 1;
>  }
>  
>  /* static int cifs_d_delete(struct dentry *direntry)
> @@ -709,15 +721,8 @@ static int cifs_ci_compare(struct dentry
>  	struct nls_table *codepage = CIFS_SB(dentry->d_inode->i_sb)->local_nls;
>  
>  	if ((a->len == b->len) &&
> -	    (nls_strnicmp(codepage, a->name, b->name, a->len) == 0)) {
> -		/*
> -		 * To preserve case, don't let an existing negative dentry's
> -		 * case take precedence.  If a is not a negative dentry, this
> -		 * should have no side effects
> -		 */
> -		memcpy((void *)a->name, b->name, a->len);
> +	    (nls_strnicmp(codepage, a->name, b->name, a->len) == 0))
>  		return 0;
> -	}
>  	return 1;
>  }
>  
> --
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Looks good to me.

Acked-by: Jeff Layton <jlayton@redhat.com>