)]}'
{
  "commit": "b009c024ff0059e293c1937516f2defe56263650",
  "tree": "35d71c837b954e884c429c9c36a85aaf7b033c49",
  "parents": [
    "212260aa07135b327752dc02625c68cf4ce04caf"
  ],
  "author": {
    "name": "Michel Lespinasse",
    "email": "walken@google.com",
    "time": "Thu Jan 13 15:46:07 2011 -0800"
  },
  "committer": {
    "name": "Linus Torvalds",
    "email": "torvalds@linux-foundation.org",
    "time": "Thu Jan 13 17:32:35 2011 -0800"
  },
  "message": "do_wp_page: remove the \u0027reuse\u0027 flag\n\nmlocking a shared, writable vma currently causes the corresponding pages\nto be marked as dirty and queued for writeback.  This seems rather\nunnecessary given that the pages are not being actually modified during\nmlock.  It is understood that for non-shared mappings (file or anon) we\nwant to use a write fault in order to break COW, but there is just no such\nneed for shared mappings.\n\nThe first two patches in this series do not introduce any behavior change.\n The intent there is to make it obvious that dirtying file pages is only\ndone in the (writable, shared) case.  I think this clarifies the code, but\nI wouldn\u0027t mind dropping these two patches if there is no consensus about\nthem.\n\nThe last patch is where we actually avoid dirtying shared mappings during\nmlock.  Note that as a side effect of this, we won\u0027t call page_mkwrite()\nfor the mappings that define it, and won\u0027t be pre-allocating data blocks\nat the FS level if the mapped file was sparsely allocated.  My\nunderstanding is that mlock does not need to provide such guarantee, as\nevidenced by the fact that it never did for the filesystems that don\u0027t\ndefine page_mkwrite() - including some common ones like ext3.  However, I\nwould like to gather feedback on this from filesystem people as a\nprecaution.  If this turns out to be a showstopper, maybe block\npreallocation can be added back on using a different interface.\n\nLarge shared mlocks are getting significantly (\u003e2x) faster in my tests, as\nthe disk can be fully used for reading the file instead of having to share\nbetween this and writeback.\n\nThis patch:\n\nReorganize the code to remove the \u0027reuse\u0027 flag.  No behavior changes.\n\nSigned-off-by: Michel Lespinasse \u003cwalken@google.com\u003e\nCc: Hugh Dickins \u003chughd@google.com\u003e\nCc: Rik van Riel \u003criel@redhat.com\u003e\nCc: Kosaki Motohiro \u003ckosaki.motohiro@jp.fujitsu.com\u003e\nCc: Peter Zijlstra \u003cpeterz@infradead.org\u003e\nCc: Nick Piggin \u003cnpiggin@kernel.dk\u003e\nCc: Theodore Tso \u003ctytso@google.com\u003e\nCc: Michael Rubin \u003cmrubin@google.com\u003e\nCc: Suleiman Souhlal \u003csuleiman@google.com\u003e\nCc: Dave Chinner \u003cdavid@fromorbit.com\u003e\nCc: Christoph Hellwig \u003chch@infradead.org\u003e\nSigned-off-by: Andrew Morton \u003cakpm@linux-foundation.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@linux-foundation.org\u003e\n",
  "tree_diff": [
    {
      "type": "modify",
      "old_id": "02e48aa0ed136ff8e4d808d954a20d0b46e6d23d",
      "old_mode": 33188,
      "old_path": "mm/memory.c",
      "new_id": "d0cc1c134a6477384c54d04223cd338875400b2f",
      "new_mode": 33188,
      "new_path": "mm/memory.c"
    }
  ]
}