This is a rather hot function that is called with a potentially NULL
"struct common_audit_data" pointer argument. And in that case it has to
provide and initialize its own dummy common_audit_data structure.
However, all the _common_ cases already pass it a real audit-data
structure, so that uncommon NULL case not only creates a silly run-time
test, more importantly it causes that function to have a big stack frame
for the dummy variable that isn't even used in the common case!
So get rid of that stupid run-time behavior, and make the (few)
functions that currently call with a NULL pointer just call a new helper
function instead (naturally called inode_has_perm_noapd(), since it has
no adp argument).
This makes the run-time test be a static code generation issue instead,
and allows for a much denser stack since none of the common callers need
the dummy structure. And a denser stack not only means less stack space
usage, it means better cache behavior. So we have a win-win-win from
this simplification: less code executed, smaller stack footprint, and
better cache behavior.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
95f4efb2d7