iommufd: Use atomic_long_try_cmpxchg() in incr_user_locked_vm()

Use atomic_long_try_cmpxchg() instead of
atomic_long_cmpxchg (*ptr, old, new) != old in incr_user_locked_vm().
cmpxchg returns success in ZF flag, so this change saves a compare
after cmpxchg (and related move instruction in front of cmpxchg).

Also, atomic_long_try_cmpxchg() implicitly assigns old *ptr
value to "old" when cmpxchg fails. There is no need to re-read
the value in the loop.

Signed-off-by: Uros Bizjak <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Kevin Tian <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Robin Murphy <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

0 files changed, 0 insertions, 0 deletions