1. 12 Sep, 2022 1 commit
    • Fabio M. De Francesco's avatar
      hfsplus: unmap the page in the "fail_page" label · f5b23d67
      Fabio M. De Francesco authored
      Patch series "hfsplus: Replace kmap() with kmap_local_page()".
      
      kmap() is being deprecated in favor of kmap_local_page().
      
      There are two main problems with kmap(): (1) It comes with an overhead as
      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.  Furthermore,
      the tasks can be preempted and, when they are scheduled to run again, the
      kernel virtual addresses are restored and still valid.
      
      Since its use in fs/hfsplus is safe everywhere, it should be preferred.
      
      Therefore, replace kmap() with kmap_local_page() in fs/hfsplus.  Where
      possible, use the suited standard helpers (memzero_page(), memcpy_page())
      instead of open coding kmap_local_page() plus memset() or memcpy().
      
      Fix a bug due to a page being not unmapped if the code jumps to the
      "fail_page" label (1/4).
      
      Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with
      HIGHMEM64GB enabled.
      
      
      This patch (of 4):
      
      Several paths within hfs_btree_open() jump to the "fail_page" label where
      put_page() is called while the page is still mapped.
      
      Call kunmap() to unmap the page soon before put_page().
      
      Link: https://lkml.kernel.org/r/20220809203105.26183-1-fmdefrancesco@gmail.com
      Link: https://lkml.kernel.org/r/20220809203105.26183-2-fmdefrancesco@gmail.comSigned-off-by: default avatarFabio M. De Francesco <fmdefrancesco@gmail.com>
      Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
      Reviewed-by: default avatarViacheslav Dubeyko <slava@dubeyko.com>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Bart Van Assche <bvanassche@acm.org>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Muchun Song <songmuchun@bytedance.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      f5b23d67
  2. 28 Aug, 2022 25 commits
  3. 27 Aug, 2022 14 commits