1. 20 7月, 2007 3 次提交
    • M
      ocfs2: release page lock before calling ->page_mkwrite · 69676147
      Mark Fasheh 提交于
      __do_fault() was calling ->page_mkwrite() with the page lock held, which
      violates the locking rules for that callback.  Release and retake the page
      lock around the callback to avoid deadlocking file systems which manually
      take it.
      Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      69676147
    • N
      mm: merge populate and nopage into fault (fixes nonlinear) · 54cb8821
      Nick Piggin 提交于
      Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes
      the virtual address -> file offset differently from linear mappings.
      
      ->populate is a layering violation because the filesystem/pagecache code
      should need to know anything about the virtual memory mapping.  The hitch here
      is that the ->nopage handler didn't pass down enough information (ie.  pgoff).
       But it is more logical to pass pgoff rather than have the ->nopage function
      calculate it itself anyway (because that's a similar layering violation).
      
      Having the populate handler install the pte itself is likewise a nasty thing
      to be doing.
      
      This patch introduces a new fault handler that replaces ->nopage and
      ->populate and (later) ->nopfn.  Most of the old mechanism is still in place
      so there is a lot of duplication and nice cleanups that can be removed if
      everyone switches over.
      
      The rationale for doing this in the first place is that nonlinear mappings are
      subject to the pagefault vs invalidate/truncate race too, and it seemed stupid
      to duplicate the synchronisation logic rather than just consolidate the two.
      
      After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in
      pagecache.  Seems like a fringe functionality anyway.
      
      NOPAGE_REFAULT is removed.  This should be implemented with ->fault, and no
      users have hit mainline yet.
      
      [akpm@linux-foundation.org: cleanup]
      [randy.dunlap@oracle.com: doc. fixes for readahead]
      [akpm@linux-foundation.org: build fix]
      Signed-off-by: NNick Piggin <npiggin@suse.de>
      Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
      Cc: Mark Fasheh <mark.fasheh@oracle.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      54cb8821
    • N
      mm: fix fault vs invalidate race for linear mappings · d00806b1
      Nick Piggin 提交于
      Fix the race between invalidate_inode_pages and do_no_page.
      
      Andrea Arcangeli identified a subtle race between invalidation of pages from
      pagecache with userspace mappings, and do_no_page.
      
      The issue is that invalidation has to shoot down all mappings to the page,
      before it can be discarded from the pagecache.  Between shooting down ptes to
      a particular page, and actually dropping the struct page from the pagecache,
      do_no_page from any process might fault on that page and establish a new
      mapping to the page just before it gets discarded from the pagecache.
      
      The most common case where such invalidation is used is in file truncation.
      This case was catered for by doing a sort of open-coded seqlock between the
      file's i_size, and its truncate_count.
      
      Truncation will decrease i_size, then increment truncate_count before
      unmapping userspace pages; do_no_page will read truncate_count, then find the
      page if it is within i_size, and then check truncate_count under the page
      table lock and back out and retry if it had subsequently been changed (ptl
      will serialise against unmapping, and ensure a potentially updated
      truncate_count is actually visible).
      
      Complexity and documentation issues aside, the locking protocol fails in the
      case where we would like to invalidate pagecache inside i_size.  do_no_page
      can come in anytime and filemap_nopage is not aware of the invalidation in
      progress (as it is when it is outside i_size).  The end result is that
      dangling (->mapping == NULL) pages that appear to be from a particular file
      may be mapped into userspace with nonsense data.  Valid mappings to the same
      place will see a different page.
      
      Andrea implemented two working fixes, one using a real seqlock, another using
      a page->flags bit.  He also proposed using the page lock in do_no_page, but
      that was initially considered too heavyweight.  However, it is not a global or
      per-file lock, and the page cacheline is modified in do_no_page to increment
      _count and _mapcount anyway, so a further modification should not be a large
      performance hit.  Scalability is not an issue.
      
      This patch implements this latter approach.  ->nopage implementations return
      with the page locked if it is possible for their underlying file to be
      invalidated (in that case, they must set a special vm_flags bit to indicate
      so).  do_no_page only unlocks the page after setting up the mapping
      completely.  invalidation is excluded because it holds the page lock during
      invalidation of each page (and ensures that the page is not mapped while
      holding the lock).
      
      This also allows significant simplifications in do_no_page, because we have
      the page locked in the right place in the pagecache from the start.
      Signed-off-by: NNick Piggin <npiggin@suse.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d00806b1
  2. 18 7月, 2007 37 次提交