1. 04 Apr, 2016 1 commit
    • Kirill A. Shutemov's avatar
      mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros · 09cbfeaf
      Kirill A. Shutemov authored
      PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
      ago with promise that one day it will be possible to implement page
      cache with bigger chunks than PAGE_SIZE.
      
      This promise never materialized.  And unlikely will.
      
      We have many places where PAGE_CACHE_SIZE assumed to be equal to
      PAGE_SIZE.  And it's constant source of confusion on whether
      PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
      especially on the border between fs and mm.
      
      Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
      breakage to be doable.
      
      Let's stop pretending that pages in page cache are special.  They are
      not.
      
      The changes are pretty straight-forward:
      
       - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
      
       - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
      
       - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};
      
       - page_cache_get() -> get_page();
      
       - page_cache_release() -> put_page();
      
      This patch contains automated changes generated with coccinelle using
      script below.  For some reason, coccinelle doesn't patch header files.
      I've called spatch for them manually.
      
      The only adjustment after coccinelle is revert of changes to
      PAGE_CAHCE_ALIGN definition: we are going to drop it later.
      
      There are few places in the code where coccinelle didn't reach.  I'll
      fix them manually in a separate patch.  Comments and documentation also
      will be addressed with the separate patch.
      
      virtual patch
      
      @@
      expression E;
      @@
      - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
      + E
      
      @@
      expression E;
      @@
      - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
      + E
      
      @@
      @@
      - PAGE_CACHE_SHIFT
      + PAGE_SHIFT
      
      @@
      @@
      - PAGE_CACHE_SIZE
      + PAGE_SIZE
      
      @@
      @@
      - PAGE_CACHE_MASK
      + PAGE_MASK
      
      @@
      expression E;
      @@
      - PAGE_CACHE_ALIGN(E)
      + PAGE_ALIGN(E)
      
      @@
      expression E;
      @@
      - page_cache_get(E)
      + get_page(E)
      
      @@
      expression E;
      @@
      - page_cache_release(E)
      + put_page(E)
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      09cbfeaf
  2. 20 Nov, 2013 2 commits
    • Phillip Lougher's avatar
      Squashfs: Directly decompress into the page cache for file data · 0d455c12
      Phillip Lougher authored
      This introduces an implementation of squashfs_readpage_block()
      that directly decompresses into the page cache.
      
      This uses the previously added page handler abstraction to push
      down the necessary kmap_atomic/kunmap_atomic operations on the
      page cache buffers into the decompressors.  This enables
      direct copying into the page cache without using the slow
      kmap/kunmap calls.
      
      The code detects when multiple threads are racing in
      squashfs_readpage() to decompress the same block, and avoids
      this regression by falling back to using an intermediate
      buffer.
      
      This patch enhances the performance of Squashfs significantly
      when multiple processes are accessing the filesystem simultaneously
      because it not only reduces memcopying, but it more importantly
      eliminates the lock contention on the intermediate buffer.
      
      Using single-thread decompression.
      
              dd if=file1 of=/dev/null bs=4096 &
              dd if=file2 of=/dev/null bs=4096 &
              dd if=file3 of=/dev/null bs=4096 &
              dd if=file4 of=/dev/null bs=4096
      
      Before:
      
      629145600 bytes (629 MB) copied, 45.8046 s, 13.7 MB/s
      
      After:
      
      629145600 bytes (629 MB) copied, 9.29414 s, 67.7 MB/s
      Signed-off-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
      Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
      0d455c12
    • Phillip Lougher's avatar
      Squashfs: Generalise paging handling in the decompressors · 846b730e
      Phillip Lougher authored
      Further generalise the decompressors by adding a page handler
      abstraction.  This adds helpers to allow the decompressors
      to access and process the output buffers in an implementation
      independant manner.
      
      This allows different types of output buffer to be passed
      to the decompressors, with the implementation specific
      aspects handled at decompression time, but without the
      knowledge being held in the decompressor wrapper code.
      
      This will allow the decompressors to handle Squashfs
      cache buffers, and page cache pages.
      
      This patch adds the abstraction and an implementation for
      the caches.
      Signed-off-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
      Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
      846b730e