Commit 4c7a6f74 authored by Wang Shilong's avatar Wang Shilong Committed by Chris Mason
Browse files

Btrfs: rework ulist with list+rb_tree 



We are really suffering from now ulist's implementation, some developers
gave their try, and i just gave some of my ideas for things:

 1. use list+rb_tree instead of arrary+rb_tree

 2. add cur_list to iterator rather than ulist structure.

 3. add seqnum into every node when they are added, this is
 used to do selfcheck when iterating node.

I noticed Zach Brown's comments before, long term is to kick off
ulist implementation, however, for now, we need at least avoid
arrary from ulist.

Cc: Liu Bo <bo.li.liu@oracle.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Zach Brown <zab@redhat.com>
Signed-off-by: default avatarWang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent f05c4746

fs/btrfs/ulist.c

+44 −61
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <linux/slab.h>

#include <linux/export.h>

#include "ulist.h"

#include "ctree.h"



/*

 * ulist is a generic data structure to hold a collection of unique u64
@@ -14,10 +15,6 @@ 
 * enumerating it.

 * It is possible to store an auxiliary value along with the key.

 *

 * The implementation is preliminary and can probably be sped up

 * significantly. A first step would be to store the values in an rbtree

 * as soon as ULIST_SIZE is exceeded.

 *

 * A sample usage for ulists is the enumeration of directed graphs without

 * visiting a node twice. The pseudo-code could look like this:

 *
@@ -50,10 +47,9 @@ 
 */

void ulist_init(struct ulist *ulist)

{

	ulist->nnodes = 0;

	ulist->nodes = ulist->int_nodes;

	ulist->nodes_alloced = ULIST_SIZE;

	INIT_LIST_HEAD(&ulist->nodes);

	ulist->root = RB_ROOT;

	ulist->nnodes = 0;

}

EXPORT_SYMBOL(ulist_init);
@@ -66,14 +62,14 @@ EXPORT_SYMBOL(ulist_init); 
 */

void ulist_fini(struct ulist *ulist)

{

	/*

	 * The first ULIST_SIZE elements are stored inline in struct ulist.

	 * Only if more elements are alocated they need to be freed.

	 */

	if (ulist->nodes_alloced > ULIST_SIZE)

		kfree(ulist->nodes);

	ulist->nodes_alloced = 0;	/* in case ulist_fini is called twice */

	struct ulist_node *node;

	struct ulist_node *next;



	list_for_each_entry_safe(node, next, &ulist->nodes, list) {

		kfree(node);

	}

	ulist->root = RB_ROOT;

	INIT_LIST_HEAD(&ulist->nodes);

}

EXPORT_SYMBOL(ulist_fini);
@@ -192,57 +188,29 @@ int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask) 
int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,

		    u64 *old_aux, gfp_t gfp_mask)

{

	int ret = 0;

	struct ulist_node *node = NULL;

	int ret;

	struct ulist_node *node;



	node = ulist_rbtree_search(ulist, val);

	if (node) {

		if (old_aux)

			*old_aux = node->aux;

		return 0;

	}



	if (ulist->nnodes >= ulist->nodes_alloced) {

		u64 new_alloced = ulist->nodes_alloced + 128;

		struct ulist_node *new_nodes;

		void *old = NULL;

		int i;



		/*

		 * if nodes_alloced == ULIST_SIZE no memory has been allocated

		 * yet, so pass NULL to krealloc

		 */

		if (ulist->nodes_alloced > ULIST_SIZE)

			old = ulist->nodes;



		new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,

				     gfp_mask);

		if (!new_nodes)

	node = kmalloc(sizeof(*node), gfp_mask);

	if (!node)

		return -ENOMEM;



		if (!old)

			memcpy(new_nodes, ulist->int_nodes,

			       sizeof(ulist->int_nodes));

	node->val = val;

	node->aux = aux;

#ifdef CONFIG_BTRFS_DEBUG

	node->seqnum = ulist->nnodes;

#endif



		ulist->nodes = new_nodes;

		ulist->nodes_alloced = new_alloced;



		/*

		 * krealloc actually uses memcpy, which does not copy rb_node

		 * pointers, so we have to do it ourselves.  Otherwise we may

		 * be bitten by crashes.

		 */

		ulist->root = RB_ROOT;

		for (i = 0; i < ulist->nnodes; i++) {

			ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);

			if (ret < 0)

				return ret;

		}

	}

	ulist->nodes[ulist->nnodes].val = val;

	ulist->nodes[ulist->nnodes].aux = aux;

	ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);

	BUG_ON(ret);

	++ulist->nnodes;

	ret = ulist_rbtree_insert(ulist, node);

	ASSERT(!ret);

	list_add_tail(&node->list, &ulist->nodes);

	ulist->nnodes++;



	return 1;

}
@@ -266,11 +234,26 @@ EXPORT_SYMBOL(ulist_add); 
 */

struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)

{

	if (ulist->nnodes == 0)

	struct ulist_node *node;



	if (list_empty(&ulist->nodes))

		return NULL;

	if (uiter->i < 0 || uiter->i >= ulist->nnodes)

	if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)

		return NULL;



	return &ulist->nodes[uiter->i++];

	if (uiter->cur_list) {

		uiter->cur_list = uiter->cur_list->next;

	} else {

		uiter->cur_list = ulist->nodes.next;

#ifdef CONFIG_BTRFS_DEBUG

		uiter->i = 0;

#endif

	}

	node = list_entry(uiter->cur_list, struct ulist_node, list);

#ifdef CONFIG_BTRFS_DEBUG

	ASSERT(node->seqnum == uiter->i);

	ASSERT(uiter->i >= 0 && uiter->i < ulist->nnodes);

	uiter->i++;

#endif

	return node;

}

EXPORT_SYMBOL(ulist_next);

fs/btrfs/ulist.h

+11 −27
Original line number Diff line number Diff line
@@ -17,18 +17,12 @@ 
 * enumerating it.

 * It is possible to store an auxiliary value along with the key.

 *

 * The implementation is preliminary and can probably be sped up

 * significantly. A first step would be to store the values in an rbtree

 * as soon as ULIST_SIZE is exceeded.

 */



/*

 * number of elements statically allocated inside struct ulist

 */

#define ULIST_SIZE 16



struct ulist_iterator {

#ifdef CONFIG_BTRFS_DEBUG

	int i;

#endif

	struct list_head *cur_list;  /* hint to start search */

};



/*
@@ -37,6 +31,12 @@ struct ulist_iterator { 
struct ulist_node {

	u64 val;		/* value to store */

	u64 aux;		/* auxiliary value saved along with the val */



#ifdef CONFIG_BTRFS_DEBUG

	int seqnum;		/* sequence number this node is added */

#endif



	struct list_head list;  /* used to link node */

	struct rb_node rb_node;	/* used to speed up search */

};
@@ -46,24 +46,8 @@ struct ulist { 
	 */

	unsigned long nnodes;



	/*

	 * number of nodes we already have room for

	 */

	unsigned long nodes_alloced;



	/*

	 * pointer to the array storing the elements. The first ULIST_SIZE

	 * elements are stored inline. In this case the it points to int_nodes.

	 * After exceeding ULIST_SIZE, dynamic memory is allocated.

	 */

	struct ulist_node *nodes;



	struct list_head nodes;

	struct rb_root root;



	/*

	 * inline storage space for the first ULIST_SIZE entries

	 */

	struct ulist_node int_nodes[ULIST_SIZE];

};



void ulist_init(struct ulist *ulist);
@@ -77,6 +61,6 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux, 
struct ulist_node *ulist_next(struct ulist *ulist,

			      struct ulist_iterator *uiter);



#define ULIST_ITER_INIT(uiter) ((uiter)->i = 0)

#define ULIST_ITER_INIT(uiter) ((uiter)->cur_list = NULL)



#endif

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