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dax: Flush partial PMDs correctly

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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: c1901cd33c ("page cache: Convert find_get_entries_tag to XArray")
Cc: <stable@vger.kernel.org>
Reported-by: Piotr Balcer <piotr.balcer@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Matthew Wilcox 2019-03-01 11:12:41 -08:00 committed by Dan Williams
parent 0cefc36b32
commit e4b3448bc3
1 changed files with 9 additions and 10 deletions
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19
fs/dax.c
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@ -843,9 +843,8 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
struct address_space *mapping, void *entry)
{
unsigned long pfn;
unsigned long pfn, index, count;
long ret = 0;
size_t size;
/*
* A page got tagged dirty in DAX mapping? Something is seriously
@ -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 use needs to be
* aligned to the start 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);
dax_entry_mkclean(mapping, xas->xa_index, pfn);
dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
dax_entry_mkclean(mapping, index, pfn);
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, index, count);
return ret;
put_unlocked: