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dax: Convert dax_layout_busy_page to XArray 

Instead of using a pagevec, just use the XArray iterators.  Add a
conditional rescheduling point which probably should have been there in
the original.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-05-17 13:03:48 -04:00
parent cfc93c6c6c
commit 084a899008
1 changed files with 21 additions and 43 deletions
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64
fs/dax.c
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@ -722,11 +722,10 @@ restart:
*/
struct page *dax_layout_busy_page(struct address_space *mapping)
{
pgoff_t indices[PAGEVEC_SIZE];
XA_STATE(xas, &mapping->i_pages, 0);
void *entry;
unsigned int scanned = 0;
struct page *page = NULL;
struct pagevec pvec;
pgoff_t index, end;
unsigned i;
/*
* In the 'limited' case get_user_pages() for dax is disabled.
@ -737,13 +736,9 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
if (!dax_mapping(mapping) || !mapping_mapped(mapping))
return NULL;
pagevec_init(&pvec);
index = 0;
end = -1;
/*
* If we race get_user_pages_fast() here either we'll see the
* elevated page count in the pagevec_lookup and wait, or
* elevated page count in the iteration and wait, or
* get_user_pages_fast() will see that the page it took a reference
* against is no longer mapped in the page tables and bail to the
* get_user_pages() slow path. The slow path is protected by
@ -755,43 +750,26 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
*/
unmap_mapping_range(mapping, 0, 0, 1);
while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
min(end - index, (pgoff_t)PAGEVEC_SIZE),
indices)) {
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *pvec_ent = pvec.pages[i];
void *entry;
index = indices[i];
if (index >= end)
break;
if (WARN_ON_ONCE(!xa_is_value(pvec_ent)))
continue;
xa_lock_irq(&mapping->i_pages);
entry = get_unlocked_mapping_entry(mapping, index, NULL);
if (entry)
page = dax_busy_page(entry);
put_unlocked_mapping_entry(mapping, index, entry);
xa_unlock_irq(&mapping->i_pages);
if (page)
break;
}
/*
* We don't expect normal struct page entries to exist in our
* tree, but we keep these pagevec calls so that this code is
* consistent with the common pattern for handling pagevecs
* throughout the kernel.
*/
pagevec_remove_exceptionals(&pvec);
pagevec_release(&pvec);
index++;
xas_lock_irq(&xas);
xas_for_each(&xas, entry, ULONG_MAX) {
if (WARN_ON_ONCE(!xa_is_value(entry)))
continue;
if (unlikely(dax_is_locked(entry)))
entry = get_unlocked_entry(&xas);
if (entry)
page = dax_busy_page(entry);
put_unlocked_entry(&xas, entry);
if (page)
break;
if (++scanned % XA_CHECK_SCHED)
continue;
xas_pause(&xas);
xas_unlock_irq(&xas);
cond_resched();
xas_lock_irq(&xas);
}
xas_unlock_irq(&xas);
return page;
}
EXPORT_SYMBOL_GPL(dax_layout_busy_page);