diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2024-05-22 10:26:49 +0200 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2024-06-25 14:21:10 +0200 |
| commit | b95a40122a8183873736e0506df8e3a881178099 (patch) | |
| tree | 261ca382465877f76dae4ec35677440fd0d4e5d4 | |
| parent | c94ad1d5e3885bd4fa6abb695baf5a8f5c3c309c (diff) | |
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 <ubizjak@gmail.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240522082729.971123-3-ubizjak@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
| -rw-r--r-- | drivers/iommu/iommufd/pages.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c index 528f356238b3..117f644a0c5b 100644 --- a/drivers/iommu/iommufd/pages.c +++ b/drivers/iommu/iommufd/pages.c @@ -809,13 +809,14 @@ static int incr_user_locked_vm(struct iopt_pages *pages, unsigned long npages) lock_limit = task_rlimit(pages->source_task, RLIMIT_MEMLOCK) >> PAGE_SHIFT; + + cur_pages = atomic_long_read(&pages->source_user->locked_vm); do { - cur_pages = atomic_long_read(&pages->source_user->locked_vm); new_pages = cur_pages + npages; if (new_pages > lock_limit) return -ENOMEM; - } while (atomic_long_cmpxchg(&pages->source_user->locked_vm, cur_pages, - new_pages) != cur_pages); + } while (!atomic_long_try_cmpxchg(&pages->source_user->locked_vm, + &cur_pages, new_pages)); return 0; } |