On Sat, Feb 16, 2019 at 07:35:11AM -0800, Matthew Wilcox wrote:
> Another way to fix this would be to mask the address in dax_entry_mkclean(),
> but I think this is cleaner.
That's clearly rubbish, dax_entry_mkclean() can't possibly mask the
address. It might be mis-aligned in another process. But ... if it's
misaligned in another process, dax_entry_mkclean() will only clean the first
PTE associated with the PMD; it won't clean the whole thing. I think we need
something like this:
(I'll have to split it apart to give us something to backport)
diff --git a/fs/dax.c b/fs/dax.c
index 6959837cc465..09680aa0481f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -768,7 +768,7 @@ unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
/* Walk all mappings of a given index of a file and writeprotect them */
static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
- unsigned long pfn)
+ pgoff_t end, unsigned long pfn)
{
struct vm_area_struct *vma;
pte_t pte, *ptep = NULL;
@@ -776,7 +776,7 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
spinlock_t *ptl;
i_mmap_lock_read(mapping);
- vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, index, end) {
struct mmu_notifier_range range;
unsigned long address;
@@ -843,9 +843,9 @@ 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;
long ret = 0;
- size_t size;
+ unsigned long count;
/*
* A page got tagged dirty in DAX mapping? Something is seriously
@@ -894,17 +894,18 @@ 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);
- dax_entry_mkclean(mapping, xas->xa_index, pfn);
- dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
+ dax_entry_mkclean(mapping, index, index + count - 1, 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 +918,7 @@ 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:
