dax_layout_busy_warn_on_not_exceptional

   1 dax: dax_layout_busy_page() warn on !exceptional
   2
   3 From: Ross Zwisler <ross.zwisler@linux.intel.com>
   4
   5 Inodes using DAX should only ever have exceptional entries in their page
   6 caches.  Make this clear by warning if the iteration in
   7 dax_layout_busy_page() ever sees a non-exceptional entry, and by adding a
   8 comment for the pagevec_release() call which only deals with struct page
   9 pointers.
  10
  11 Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
  12 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  13 Reviewed-by: Jan Kara <jack@suse.cz>
  14 ---
  15  fs/dax.c | 10 +++++++++-
  16  1 file changed, 9 insertions(+), 1 deletion(-)
  17
  18 diff --git a/fs/dax.c b/fs/dax.c
  19 index 641192808bb6..897b51e41d8f 100644
  20 --- a/fs/dax.c
  21 +++ b/fs/dax.c
  22 @@ -566,7 +566,8 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
  23                         if (index >= end)
  24                                 break;
  25
  26 -                       if (!radix_tree_exceptional_entry(pvec_ent))
  27 +                       if (WARN_ON_ONCE(
  28 +                            !radix_tree_exceptional_entry(pvec_ent)))
  29                                 continue;
  30
  31                         xa_lock_irq(&mapping->i_pages);
  32 @@ -578,6 +579,13 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
  33                         if (page)
  34                                 break;
  35                 }
  36 +
  37 +               /*
  38 +                * We don't expect normal struct page entries to exist in our
  39 +                * tree, but we keep these pagevec calls so that this code is
  40 +                * consistent with the common pattern for handling pagevecs
  41 +                * throughout the kernel.
  42 +                */
  43                 pagevec_remove_exceptionals(&pvec);
  44                 pagevec_release(&pvec);
  45                 index++;
  46 --
  47 2.14.4
  48
  49