[PATCH v9 1/4] unicode: Add utf8_casefold_hash

[Eric Biggers]

On Tue, Jun 23, 2020 at 09:33:38PM -0700, Daniel Rosenberg wrote:
> This adds a case insensitive hash function to allow taking the hash
> without needing to allocate a casefolded copy of the string.

It would be helpful to add a few more details in this commit message.
Somewhat along the lines of: ->d_hash() for casefolding currently allocates
memory, it needs to use GFP_ATOMIC due to ->d_hash() being called in rcu-walk
mode, this is unreliable and inefficient, and this patch allows solving that
problem by removing the need to allocate memory.

- Eric