Re: [PATCH 5/5] quota: handle IO errors in dquot_transfer()

[Jan Kara <jack@suse.cz>]

On Mon 14-12-09 15:21:16, Dmitry Monakhov wrote:
> transfer_to[cnt] = dqget() may returns NULL due to IO error.
> But NULL value in transfer_to[cnt] means a dquot transfer
> optimization. So after operation succeed inode will have new
> i_uid or i_gid but accounted to old dquot. This behaviour
> is differ from dquot_initialize(). Let's handle IO error from
> dqget() equally in all functions.
> 
> In appliance to dquot_transfer() this means that we have to finish
> operation regardless to IO errors from dqget().
  In principle, the patch is fine (see just about a bug below). But even
better would be if you converted dquot_transfer() to actually return real
return codes (0, -EDQUOT, -EIO...) and make it return EIO in case of IO
error. Then a filesystem can properly fail chown if quota transfer cannot
be performed. This is a larger project since filesystems using
dquot_transfer need to be changed and also other dquot_... functions need
to be converted to this calling convention for the sake of consistency. But
it would be a good cleanup.

...
>  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> -		transfer_from[cnt] = NULL;
> -		transfer_to[cnt] = NULL;
>  		warntype_to[cnt] = QUOTA_NL_NOWARN;
> +		if (!valid[cnt])
> +			continue;
> +		transfer_to[cnt] = dqget(inode->i_sb, iattr->ia_uid, cnt);
  This is wrong! You have to take ia_gid in case of GRPQUOTA.

> @@ -1767,9 +1769,11 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
>  	space = cur_space + rsv_space;
>  	/* Build the transfer_from list and check the limits */
>  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> -		if (!transfer_to[cnt])
> +		if (!valid[cnt])
>  			continue;
>  		transfer_from[cnt] = inode->i_dquot[cnt];
> +		if (!transfer_to[cnt])
> +			continue;
>  		if (check_idq(transfer_to[cnt], 1, warntype_to + cnt) ==
>  		    NO_QUOTA || check_bdq(transfer_to[cnt], space, 0,
>  		    warntype_to + cnt) == NO_QUOTA)
> @@ -1783,10 +1787,15 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
>  		/*
>  		 * Skip changes for same uid or gid or for turned off quota-type.
>  		 */
> -		if (!transfer_to[cnt])
> +		if (!valid[cnt])
>  			continue;
> +		/*
> +		 * Due to IO error we might not have transfer_to[] or
> +		 * transfer_from[] structure. Nor than less the operation must
                                              ^^ I suppose this should be
"Nonetheless"
> +		 * being done regardless quota io errors.
> +		 */
> +		inode->i_dquot[cnt] = transfer_to[cnt];
>  
> -		/* Due to IO error we might not have transfer_from[] structure */
>  		if (transfer_from[cnt]) {
>  			warntype_from_inodes[cnt] =
>  				info_idq_free(transfer_from[cnt], 1);
> @@ -1797,12 +1806,11 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
>  			dquot_free_reserved_space(transfer_from[cnt],
>  						  rsv_space);
>  		}
> -
> -		dquot_incr_inodes(transfer_to[cnt], 1);
> -		dquot_incr_space(transfer_to[cnt], cur_space);
> -		dquot_resv_space(transfer_to[cnt], rsv_space);
> -
> -		inode->i_dquot[cnt] = transfer_to[cnt];
> +		if (transfer_to[cnt]) {
> +			dquot_incr_inodes(transfer_to[cnt], 1);
> +			dquot_incr_space(transfer_to[cnt], cur_space);
> +			dquot_resv_space(transfer_to[cnt], rsv_space);
> +		}
>  	}
>  	spin_unlock(&dq_data_lock);
>  	up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
> -- 
> 1.6.0.4
> 
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR