queue-5.0/dax-flush-partial-pmds-correctly.patch

   1 From e4b3448bc346fedf36db64124a664a959995b085 Mon Sep 17 00:00:00 2001
   2 From: Matthew Wilcox <willy@infradead.org>
   3 Date: Fri, 1 Mar 2019 11:12:41 -0800
   4 Subject: dax: Flush partial PMDs correctly
   5
   6 From: Matthew Wilcox <willy@infradead.org>
   7
   8 commit e4b3448bc346fedf36db64124a664a959995b085 upstream.
   9
  10 The radix tree would rewind the index in an iterator to the lowest index
  11 of a multi-slot entry.  The XArray iterators instead leave the index
  12 unchanged, but I overlooked that when converting DAX from the radix tree
  13 to the XArray.  Adjust the index that we use for flushing to the start
  14 of the PMD range.
  15
  16 Fixes: c1901cd33cf4 ("page cache: Convert find_get_entries_tag to XArray")
  17 Cc: <stable@vger.kernel.org>
  18 Reported-by: Piotr Balcer <piotr.balcer@intel.com>
  19 Tested-by: Dan Williams <dan.j.williams@intel.com>
  20 Reviewed-by: Jan Kara <jack@suse.cz>
  21 Signed-off-by: Matthew Wilcox <willy@infradead.org>
  22 Signed-off-by: Dan Williams <dan.j.williams@intel.com>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24
  25 ---
  26  fs/dax.c |   19 +++++++++----------
  27  1 file changed, 9 insertions(+), 10 deletions(-)
  28
  29 --- a/fs/dax.c
  30 +++ b/fs/dax.c
  31 @@ -843,9 +843,8 @@ unlock_pte:
  32  static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
  33                 struct address_space *mapping, void *entry)
  34  {
  35 -       unsigned long pfn;
  36 +       unsigned long pfn, index, count;
  37         long ret = 0;
  38 -       size_t size;
  39
  40         /*
  41          * A page got tagged dirty in DAX mapping? Something is seriously
  42 @@ -894,17 +893,18 @@ static int dax_writeback_one(struct xa_s
  43         xas_unlock_irq(xas);
  44
  45         /*
  46 -        * Even if dax_writeback_mapping_range() was given a wbc->range_start
  47 -        * in the middle of a PMD, the 'index' we are given will be aligned to
  48 -        * the start index of the PMD, as will the pfn we pull from 'entry'.
  49 +        * If dax_writeback_mapping_range() was given a wbc->range_start
  50 +        * in the middle of a PMD, the 'index' we use needs to be
  51 +        * aligned to the start of the PMD.
  52          * This allows us to flush for PMD_SIZE and not have to worry about
  53          * partial PMD writebacks.
  54          */
  55         pfn = dax_to_pfn(entry);
  56 -       size = PAGE_SIZE << dax_entry_order(entry);
  57 +       count = 1UL << dax_entry_order(entry);
  58 +       index = xas->xa_index & ~(count - 1);
  59
  60 -       dax_entry_mkclean(mapping, xas->xa_index, pfn);
  61 -       dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
  62 +       dax_entry_mkclean(mapping, index, pfn);
  63 +       dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_SIZE);
  64         /*
  65          * After we have flushed the cache, we can clear the dirty tag. There
  66          * cannot be new dirty data in the pfn after the flush has completed as
  67 @@ -917,8 +917,7 @@ static int dax_writeback_one(struct xa_s
  68         xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
  69         dax_wake_entry(xas, entry, false);
  70
  71 -       trace_dax_writeback_one(mapping->host, xas->xa_index,
  72 -                       size >> PAGE_SHIFT);
  73 +       trace_dax_writeback_one(mapping->host, index, count);
  74         return ret;
  75
  76   put_unlocked: