On Thu 28-02-19 20:24:48, Matthew Wilcox wrote:
The radix tree would rewind the index in an iterator to the lowest
of a multi-slot entry. The XArray iterators instead leave the index
unchanged, but I overlooked that when converting DAX from the radix tree
to the XArray. Adjust the index that we use for flushing to the start
of the PMD range.
Fixes: c1901cd33cf4 "page cache: Convert find_get_entries_tag to XArray"
Reported-by: Piotr Balcer <piotr.balcer(a)intel.com>
Tested-by: Dan Williams <dan.j.williams(a)intel.com>
Signed-off-by: Matthew Wilcox <willy(a)infradead.org>
Thanks for the patch! One comment below:
@@ -894,17 +893,18 @@ static int dax_writeback_one(struct xa_state
*xas, struct dax_device *dax_dev,
- * Even if dax_writeback_mapping_range() was given a wbc->range_start
- * in the middle of a PMD, the 'index' we are given will be aligned to
- * the start index of the PMD, as will the pfn we pull from 'entry'.
+ * If dax_writeback_mapping_range() was given a wbc->range_start
+ * in the middle of a PMD, the 'index' we are given needs to be
+ * aligned to the start index of the PMD.
* This allows us to flush for PMD_SIZE and not have to worry about
* partial PMD writebacks.
pfn = dax_to_pfn(entry);
- size = PAGE_SIZE << dax_entry_order(entry);
+ count = 1UL << dax_entry_order(entry);
+ index = xas->xa_index &~ (count - 1);
Hum, why do you compute 'index' here when you actually never use it? The
whole patch looks fishy since it is effectively a noop AFAICT...
dax_entry_mkclean(mapping, xas->xa_index, pfn);
- dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
+ dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_SIZE);
* After we have flushed the cache, we can clear the dirty tag. There
* cannot be new dirty data in the pfn after the flush has completed as
@@ -917,8 +917,7 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device
dax_wake_entry(xas, entry, false);
- trace_dax_writeback_one(mapping->host, xas->xa_index,
- size >> PAGE_SHIFT);
+ trace_dax_writeback_one(mapping->host, xas->xa_index, count);
Jan Kara <jack(a)suse.com>
SUSE Labs, CR