Re: [PATCH v3 09/28] fsverity: pass log_blocksize to end_enable_verity()

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Oct 11, 2023 at 01:17:36PM +0200, Andrey Albershteyn wrote:
> On 2023-10-10 20:19:06, Eric Biggers wrote:
> > On Fri, Oct 06, 2023 at 08:49:03PM +0200, Andrey Albershteyn wrote:
> > > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
> > > index 252b2668894c..cac012d4c86a 100644
> > > --- a/include/linux/fsverity.h
> > > +++ b/include/linux/fsverity.h
> > > @@ -51,6 +51,7 @@ struct fsverity_operations {
> > >  	 * @desc: the verity descriptor to write, or NULL on failure
> > >  	 * @desc_size: size of verity descriptor, or 0 on failure
> > >  	 * @merkle_tree_size: total bytes the Merkle tree took up
> > > +	 * @log_blocksize: log size of the Merkle tree block
> > >  	 *
> > >  	 * If desc == NULL, then enabling verity failed and the filesystem only
> > >  	 * must do any necessary cleanups.  Else, it must also store the given
> > > @@ -65,7 +66,8 @@ struct fsverity_operations {
> > >  	 * Return: 0 on success, -errno on failure
> > >  	 */
> > >  	int (*end_enable_verity)(struct file *filp, const void *desc,
> > > -				 size_t desc_size, u64 merkle_tree_size);
> > > +				 size_t desc_size, u64 merkle_tree_size,
> > > +				 u8 log_blocksize);
> > 
> > Maybe just pass the block_size itself instead of log2(block_size)?
> 
> XFS will still do `index << log2(block_size)` to get block's offset.
> So, not sure if there's any difference.

It's only used in the following:

	offset = 0;
	for (index = 1; offset < merkle_tree_size; index++) {
		xfs_fsverity_merkle_key_to_disk(&name, offset);
		args.name = (const uint8_t *)&name.merkleoff;
		args.attr_filter = XFS_ATTR_VERITY;
		error = xfs_attr_set(&args);
		offset = index << log_blocksize;
	}

... which can be the following instead:

	for (offset = 0; offset < merkle_tree_size; offset += block_size) {
		xfs_fsverity_merkle_key_to_disk(&name, offset);
		args.name = (const uint8_t *)&name.merkleoff;
		args.attr_filter = XFS_ATTR_VERITY;
		error = xfs_attr_set(&args);
	}