[Ocfs2-devel] [PATCH 1/3] ext3/ext4: Factor out disk addressability check

[Andreas Dilger]

On 2010-08-12, at 14:15, Joel Becker wrote:

> On Thu, Aug 12, 2010 at 12:45:41PM -0600, Andreas Dilger wrote:
>> On 2010-08-12, at 11:42, Joel Becker wrote:
>>>> +int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
>>>> +{
>>>> +	u64 last_fs_block = num_blocks - 1;
>>>> +
>>>> +	BUG_ON(blocksize_bits < 9);
>>>> +	BUG_ON(blocksize_bits > PAGE_CACHE_SHIFT);
>> 
>> I'd rather not have a BUG_ON() for a "check" function that may be called with on-disk values by some filesystem.  Some filesystems (AFAIR) also handle blocksize > PAGE_SIZE internally, so this helper would not be useful for them.
> 
> 	Filesystems that handle their own page cache certainly wouldn't
> be interested in a generic helper anyway.  All of our pagecache assumes
> blocks between 512<->PAGE_CACHE_SIZE.
> 	If I change the BUG_ON()s to -EINVAL, does that work?  Or do you
> have some way you'd like to allow non-pagecache filesystems to use this
> as well?

That's probably fine for now.  If anyone complains, we can always change it later, since they can't possibly depend on this function yet...

Cheers, Andreas