On Thu 28-02-19 20:24:48, Matthew Wilcox wrote: > The radix tree would rewind the index in an iterator to the lowest index > 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@xxxxxxxxx> > Tested-by: Dan Williams <dan.j.williams@xxxxxxxxx> > Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> > --- 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, > xas_unlock_irq(xas); > > /* > - * 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... Honza > > 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_dev, > xas_clear_mark(xas, PAGECACHE_TAG_DIRTY); > 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); > return ret; > > put_unlocked: > -- > 2.20.1 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
