Merge patch series "cheaper MAY_EXEC handling for path lookup"

Mateusz Guzik <mjguzik@gmail.com> says:

In short, MAY_WRITE checks are elided.

This obsoletes the idea of pre-computing if perm checks are necessary as
that turned out to be too hairy. The new code has 2 more branches per
path component compared to that idea, but the perf difference for
typical paths (< 6 components) was basically within noise. To be
revisited if someone(tm) removes other slowdowns.

Instead of the pre-computing thing I added IOP_FASTPERM_MAY_EXEC so that
filesystems like btrfs can still avoid the hard work.

* patches from https://patch.msgid.link/20251107142149.989998-1-mjguzik@gmail.com:
  fs: retire now stale MAY_WRITE predicts in inode_permission()
  btrfs: utilize IOP_FASTPERM_MAY_EXEC
  fs: speed up path lookup with cheaper handling of MAY_EXEC

Link: https://patch.msgid.link/20251107142149.989998-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>