From: Matthew Wilcox <mawil...@microsoft.com>
Signed-off-by: Matthew Wilcox <mawil...@microsoft.com>
---
fs/dax.c | 98 +++++++++++++++++-----------------------------------------------
1 file changed, 26 insertions(+), 72 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 494e8fb7a98f..3eb0cf176d69 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -44,6 +44,7 @@
/* The 'colour' (ie low bits) within a PMD of a page offset. */
#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
+#define PMD_ORDER (PMD_SHIFT - PAGE_SHIFT)
static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
@@ -89,10 +90,10 @@ static void *dax_radix_locked_entry(sector_t sector,
unsigned long flags)
DAX_ENTRY_LOCK);
}
-static unsigned int dax_radix_order(void *entry)
+static unsigned int dax_entry_order(void *entry)
{
if (xa_to_value(entry) & DAX_PMD)
- return PMD_SHIFT - PAGE_SHIFT;
+ return PMD_ORDER;
return 0;
}
@@ -299,10 +300,11 @@ static void *grab_mapping_entry(struct address_space
*mapping, pgoff_t index,
{
XA_STATE(xas, &mapping->pages, index);
bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
- void *entry, **slot;
+ void *entry;
+ xas_set_order(&xas, index, size_flag ? PMD_ORDER : 0);
restart:
- xa_lock_irq(&mapping->pages);
+ xas_lock_irq(&xas);
entry = get_unlocked_mapping_entry(&xas);
if (WARN_ON_ONCE(entry && !xa_is_value(entry))) {
@@ -326,84 +328,36 @@ static void *grab_mapping_entry(struct address_space
*mapping, pgoff_t index,
}
}
- /* No entry for given index? Make sure radix tree is big enough. */
- if (!entry || pmd_downgrade) {
- int err;
-
- if (pmd_downgrade) {
- /*
- * Make sure 'entry' remains valid while we drop
- * xa_lock.
- */
- entry = lock_slot(&xas);
- }
-
- xa_unlock_irq(&mapping->pages);
+ if (pmd_downgrade) {
+ entry = lock_slot(&xas);
/*
* Besides huge zero pages the only other thing that gets
* downgraded are empty entries which don't need to be
* unmapped.
*/
- if (pmd_downgrade && dax_is_zero_entry(entry))
+ if (dax_is_zero_entry(entry)) {
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
unmap_mapping_range(mapping,
(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
-
- err = radix_tree_preload(
- mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
- if (err) {
- if (pmd_downgrade)
- put_locked_mapping_entry(mapping, index);
- return ERR_PTR(err);
+ xas_lock_irq(&xas);
}
- xa_lock_irq(&mapping->pages);
-
- if (!entry) {
- /*
- * We needed to drop the pages lock while calling
- * radix_tree_preload() and we didn't have an entry to
- * lock. See if another thread inserted an entry at
- * our index during this time.
- */
- entry = __radix_tree_lookup(&mapping->pages, index,
- NULL, &slot);
- if (entry) {
- radix_tree_preload_end();
- xa_unlock_irq(&mapping->pages);
- goto restart;
- }
- }
-
- if (pmd_downgrade) {
- radix_tree_delete(&mapping->pages, index);
- mapping->nrexceptional--;
- dax_wake_entry(&xas, entry, true);
- }
-
+ xas_store(&xas, NULL);
+ mapping->nrexceptional--;
+ dax_wake_entry(&xas, entry, true);
+ }
+ if (!entry || pmd_downgrade) {
entry = dax_radix_locked_entry(0, size_flag | DAX_EMPTY);
-
- err = __radix_tree_insert(&mapping->pages, index,
- dax_radix_order(entry), entry);
- radix_tree_preload_end();
- if (err) {
- xa_unlock_irq(&mapping->pages);
- /*
- * Our insertion of a DAX entry failed, most likely
- * because we were inserting a PMD entry and it
- * collided with a PTE sized entry at a different
- * index in the PMD range. We haven't inserted
- * anything into the radix tree and have no waiters to
- * wake.
- */
- return ERR_PTR(err);
- }
- /* Good, we have inserted empty locked entry into the tree. */
- mapping->nrexceptional++;
- xa_unlock_irq(&mapping->pages);
- return entry;
+ xas_store(&xas, entry);
+ if (!xas_error(&xas))
+ mapping->nrexceptional++;
+ } else {
+ entry = lock_slot(&xas);
}
- entry = lock_slot(&xas);
out_unlock:
- xa_unlock_irq(&mapping->pages);
+ xas_unlock_irq(&xas);
+ if (xas_nomem(&xas, GFP_NOIO))
+ goto restart;
return entry;
}
@@ -682,7 +636,7 @@ static int dax_writeback_one(struct block_device *bdev,
* worry about partial PMD writebacks.
*/
sector = dax_radix_sector(entry);
- size = PAGE_SIZE << dax_radix_order(entry);
+ size = PAGE_SIZE << dax_entry_order(entry);
id = dax_read_lock();
ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
--
2.15.1
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