Commit ec4907ff authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

dax: Hash on XArray instead of mapping 



Since the XArray is embedded in the struct address_space, its address
contains exactly as much entropy as the address of the mapping.  This
patch is purely preparatory for later patches which will simplify the
wait/wake interfaces.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent a77d19f4

fs/dax.c

+15 −14
Original line number Diff line number Diff line
@@ -116,7 +116,7 @@ static int dax_is_empty_entry(void *entry) 
 * DAX page cache entry locking

 */

struct exceptional_entry_key {

	struct address_space *mapping;

	struct xarray *xa;

	pgoff_t entry_start;

};
@@ -125,7 +125,7 @@ struct wait_exceptional_entry_queue { 
	struct exceptional_entry_key key;

};



static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,

static wait_queue_head_t *dax_entry_waitqueue(struct xarray *xa,

		pgoff_t index, void *entry, struct exceptional_entry_key *key)

{

	unsigned long hash;
@@ -138,21 +138,21 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping, 
	if (dax_is_pmd_entry(entry))

		index &= ~PG_PMD_COLOUR;



	key->mapping = mapping;

	key->xa = xa;

	key->entry_start = index;



	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);

	hash = hash_long((unsigned long)xa ^ index, DAX_WAIT_TABLE_BITS);

	return wait_table + hash;

}



static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode,

				       int sync, void *keyp)

static int wake_exceptional_entry_func(wait_queue_entry_t *wait,

		unsigned int mode, int sync, void *keyp)

{

	struct exceptional_entry_key *key = keyp;

	struct wait_exceptional_entry_queue *ewait =

		container_of(wait, struct wait_exceptional_entry_queue, wait);



	if (key->mapping != ewait->key.mapping ||

	if (key->xa != ewait->key.xa ||

	    key->entry_start != ewait->key.entry_start)

		return 0;

	return autoremove_wake_function(wait, mode, sync, NULL);
@@ -163,13 +163,13 @@ static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mo 
 * The important information it's conveying is whether the entry at

 * this index used to be a PMD entry.

 */

static void dax_wake_mapping_entry_waiter(struct address_space *mapping,

static void dax_wake_mapping_entry_waiter(struct xarray *xa,

		pgoff_t index, void *entry, bool wake_all)

{

	struct exceptional_entry_key key;

	wait_queue_head_t *wq;



	wq = dax_entry_waitqueue(mapping, index, entry, &key);

	wq = dax_entry_waitqueue(xa, index, entry, &key);



	/*

	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -248,7 +248,8 @@ static void *__get_unlocked_mapping_entry(struct address_space *mapping, 
			return entry;

		}



		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);

		wq = dax_entry_waitqueue(&mapping->i_pages, index, entry,

				&ewait.key);

		prepare_to_wait_exclusive(wq, &ewait.wait,

					  TASK_UNINTERRUPTIBLE);

		xa_unlock_irq(&mapping->i_pages);
@@ -289,7 +290,7 @@ static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index) 
	}

	unlock_slot(mapping, slot);

	xa_unlock_irq(&mapping->i_pages);

	dax_wake_mapping_entry_waiter(mapping, index, entry, false);

	dax_wake_mapping_entry_waiter(&mapping->i_pages, index, entry, false);

}



static void put_locked_mapping_entry(struct address_space *mapping,
@@ -309,7 +310,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping, 
		return;



	/* We have to wake up next waiter for the page cache entry lock */

	dax_wake_mapping_entry_waiter(mapping, index, entry, false);

	dax_wake_mapping_entry_waiter(&mapping->i_pages, index, entry, false);

}



static unsigned long dax_entry_size(void *entry)
@@ -578,8 +579,8 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, 
			dax_disassociate_entry(entry, mapping, false);

			radix_tree_delete(&mapping->i_pages, index);

			mapping->nrexceptional--;

			dax_wake_mapping_entry_waiter(mapping, index, entry,

					true);

			dax_wake_mapping_entry_waiter(&mapping->i_pages,

					index, entry, true);

		}



		entry = dax_make_locked(0, size_flag | DAX_EMPTY);