Commit 3159f943 authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

xarray: Replace exceptional entries 



Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries.  This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry).  It is also a change in emphasis; exceptional entries are
intimidating and different.  As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
parent 66ee620f

arch/powerpc/include/asm/book3s/64/pgtable.h

+1 −3
Original line number Diff line number Diff line
@@ -723,9 +723,7 @@ static inline bool pte_user(pte_t pte) 
	BUILD_BUG_ON(_PAGE_HPTEFLAGS & (0x1f << _PAGE_BIT_SWAP_TYPE)); \

	BUILD_BUG_ON(_PAGE_HPTEFLAGS & _PAGE_SWP_SOFT_DIRTY);	\

	} while (0)

/*

 * on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;

 */



#define SWP_TYPE_BITS 5

#define __swp_type(x)		(((x).val >> _PAGE_BIT_SWAP_TYPE) \

				& ((1UL << SWP_TYPE_BITS) - 1))

arch/powerpc/include/asm/nohash/64/pgtable.h

+1 −3
Original line number Diff line number Diff line
@@ -313,9 +313,7 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma, 
#define MAX_SWAPFILES_CHECK() do { \

	BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS); \

	} while (0)

/*

 * on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;

 */



#define SWP_TYPE_BITS 5

#define __swp_type(x)		(((x).val >> _PAGE_BIT_SWAP_TYPE) \

				& ((1UL << SWP_TYPE_BITS) - 1))

drivers/gpu/drm/i915/i915_gem.c

+7 −10
Original line number Diff line number Diff line
@@ -5996,7 +5996,8 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj, 
	count = __sg_page_count(sg);



	while (idx + count <= n) {

		unsigned long exception, i;

		void *entry;

		unsigned long i;

		int ret;



		/* If we cannot allocate and insert this entry, or the
@@ -6011,12 +6012,9 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj, 
		if (ret && ret != -EEXIST)

			goto scan;



		exception =

			RADIX_TREE_EXCEPTIONAL_ENTRY |

			idx << RADIX_TREE_EXCEPTIONAL_SHIFT;

		entry = xa_mk_value(idx);

		for (i = 1; i < count; i++) {

			ret = radix_tree_insert(&iter->radix, idx + i,

						(void *)exception);

			ret = radix_tree_insert(&iter->radix, idx + i, entry);

			if (ret && ret != -EEXIST)

				goto scan;

		}
@@ -6054,15 +6052,14 @@ lookup: 
	GEM_BUG_ON(!sg);



	/* If this index is in the middle of multi-page sg entry,

	 * the radixtree will contain an exceptional entry that points

	 * the radix tree will contain a value entry that points

	 * to the start of that range. We will return the pointer to

	 * the base page and the offset of this page within the

	 * sg entry's range.

	 */

	*offset = 0;

	if (unlikely(radix_tree_exception(sg))) {

		unsigned long base =

			(unsigned long)sg >> RADIX_TREE_EXCEPTIONAL_SHIFT;

	if (unlikely(xa_is_value(sg))) {

		unsigned long base = xa_to_value(sg);



		sg = radix_tree_lookup(&iter->radix, base);

		GEM_BUG_ON(!sg);

drivers/staging/erofs/utils.c

+6 −12
Original line number Diff line number Diff line
@@ -35,7 +35,6 @@ static atomic_long_t erofs_global_shrink_cnt; 


#ifdef CONFIG_EROFS_FS_ZIP



/* radix_tree and the future XArray both don't use tagptr_t yet */

struct erofs_workgroup *erofs_find_workgroup(

	struct super_block *sb, pgoff_t index, bool *tag)

{
@@ -47,9 +46,8 @@ repeat: 
	rcu_read_lock();

	grp = radix_tree_lookup(&sbi->workstn_tree, index);

	if (grp != NULL) {

		*tag = radix_tree_exceptional_entry(grp);

		grp = (void *)((unsigned long)grp &

			~RADIX_TREE_EXCEPTIONAL_ENTRY);

		*tag = xa_pointer_tag(grp);

		grp = xa_untag_pointer(grp);



		if (erofs_workgroup_get(grp, &oldcount)) {

			/* prefer to relax rcu read side */
@@ -83,9 +81,7 @@ int erofs_register_workgroup(struct super_block *sb, 
	sbi = EROFS_SB(sb);

	erofs_workstn_lock(sbi);



	if (tag)

		grp = (void *)((unsigned long)grp |

			1UL << RADIX_TREE_EXCEPTIONAL_SHIFT);

	grp = xa_tag_pointer(grp, tag);



	err = radix_tree_insert(&sbi->workstn_tree,

		grp->index, grp);
@@ -131,9 +127,7 @@ repeat: 


	for (i = 0; i < found; ++i) {

		int cnt;

		struct erofs_workgroup *grp = (void *)

			((unsigned long)batch[i] &

				~RADIX_TREE_EXCEPTIONAL_ENTRY);

		struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);



		first_index = grp->index + 1;
@@ -150,8 +144,8 @@ repeat: 
#endif

			continue;



		if (radix_tree_delete(&sbi->workstn_tree,

			grp->index) != grp) {

		if (xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,

			grp->index)) != grp) {

#ifdef EROFS_FS_HAS_MANAGED_CACHE

skip:

			erofs_workgroup_unfreeze(grp, 1);

fs/btrfs/compression.c

+1 −1
Original line number Diff line number Diff line
@@ -440,7 +440,7 @@ static noinline int add_ra_bio_pages(struct inode *inode, 
		rcu_read_lock();

		page = radix_tree_lookup(&mapping->i_pages, pg_index);

		rcu_read_unlock();

		if (page && !radix_tree_exceptional_entry(page)) {

		if (page && !xa_is_value(page)) {

			misses++;

			if (misses > 4)

				break;

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