Re: [RFC] mm: optimise generic_file_read_iter

On Fri, Aug 06, 2021 at 12:42:43PM +0100, Pavel Begunkov wrote:

Unless direct I/O path of generic_file_read_iter() ended up with an
error or a short read, it doesn't use inode. So, load inode and size
later, only when they're needed. This cuts two memory reads and also
imrpoves code generation, e.g. loads from stack.

... and the same question here.

NOTE: as a side effect, it reads inode->i_size after ->direct_IO(), and
I'm not sure whether that's valid, so would be great to get feedback
from someone who knows better.

Ought to be safe, I think, but again, how much effect have you observed
from the patch?