1. 10 Jul, 2023 1 commit
    • Fabio M. De Francesco's avatar
      fs/ecryptfs: Replace kmap() with kmap_local_page() · 8b70deb8
      Fabio M. De Francesco authored
      kmap() has been deprecated in favor of kmap_local_page().
      
      Therefore, replace kmap() with kmap_local_page() in fs/ecryptfs.
      
      There are two main problems with kmap(): (1) It comes with an overhead as
      the mapping space is restricted and protected by a global lock for
      synchronization and (2) it also requires global TLB invalidation when the
      kmap’s pool wraps and it might block when the mapping space is fully
      utilized until a slot becomes available.
      
      With kmap_local_page() the mappings are per thread, CPU local, can take
      page faults, and can be called from any context (including interrupts).
      It is faster than kmap() in kernels with HIGHMEM enabled. The tasks can
      be preempted and, when they are scheduled to run again, the kernel
      virtual addresses are restored and still valid.
      
      Obviously, thread locality implies that the kernel virtual addresses
      returned by kmap_local_page() are only valid in the context of the
      callers (i.e., they cannot be handed to other threads).
      
      The use of kmap_local_page() in fs/ecryptfs does not break the
      above-mentioned assumption, so it is allowed and preferred.
      
      Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with
      HIGHMEM64GB enabled.
      Suggested-by: default avatarIra Weiny <ira.weiny@intel.com>
      Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
      Signed-off-by: default avatar"Fabio M. De Francesco" <fmdefrancesco@gmail.com>
      Message-Id: <20230426172223.8896-2-fmdefrancesco@gmail.com>
      Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      8b70deb8
  2. 09 Jul, 2023 10 commits
  3. 08 Jul, 2023 29 commits