Convert the ioctl method syscall path to use the uverbs_api data
structures. The new uapi structure includes all the same information, just
in a different and more optimal way.
- Use attr_bkey instead of 2 level radix trees for everything related to
attributes. This includes the attribute storage, presence, and
detection of missing mandatory attributes.
- Avoid iterating over all attribute storage at finish, instead use
find_first_bit with the attr_bkey to locate only those attrs that need
cleanup.
- Organize things to always run, and always rely on, cleanup. This
avoids a bunch of tricky error unwind cases.
- Locate the method using the radix tree, and locate the attributes
using a very efficient incremental radix tree lookup
- Use the precomputed destroy_bkey to handle uobject destruction
- Use the precomputed allocation sizes and precomputed 'need_stack'
to avoid maths in the fast path. This is optimal if userspace
does not pass (many) unsupported attributes.
Overall this results in much better codegen for the attribute accessors,
everything is now stored in bitmaps or linear arrays indexed by attr_bkey.
The compiler can compute attr_bkey values at compile time for all method
attributes, meaning things like uverbs_attr_is_valid() now compile into
single instruction bit tests.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This radix tree datastructure is intended to replace the 'hash' structure
used today for parsing ioctl methods during system calls. This first
commit introduces the structure and builds it from the existing .rodata
descriptions.
The so-called hash arrangement is actually a 5 level open coded radix tree.
This new version uses a 3 level radix tree built using the radix tree
library.
Overall this is much less code and much easier to build as the radix tree
API allows for dynamic modification during the building. There is a small
memory penalty to pay for this, but since the radix tree is allocated on
a per device basis, a few kb of RAM seems immaterial considering the
gained simplicity.
The radix tree is similar to the existing tree, but also has a 'attr_bkey'
concept, which is a small value'd index for each method attribute. This is
used to simplify and improve performance of everything in the next
patches.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Jason Gunthorpe