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Commit 04f17c80 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm btree: prefetch child nodes when walking tree for a dm_btree_del 



dm-btree now takes advantage of dm-bufio's ability to prefetch data via
dm_bm_prefetch().  Prior to this change many btree node visits were
causing a synchronous read.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent cd5acf0b

drivers/md/persistent-data/dm-block-manager.c

+5 −0
Original line number Diff line number Diff line
@@ -615,6 +615,11 @@ int dm_bm_flush_and_unlock(struct dm_block_manager *bm, 
}

EXPORT_SYMBOL_GPL(dm_bm_flush_and_unlock);



void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b)

{

	dm_bufio_prefetch(bm->bufio, b, 1);

}



void dm_bm_set_read_only(struct dm_block_manager *bm)

{

	bm->read_only = true;

drivers/md/persistent-data/dm-block-manager.h

+5 −0
Original line number Diff line number Diff line
@@ -108,6 +108,11 @@ int dm_bm_unlock(struct dm_block *b); 
int dm_bm_flush_and_unlock(struct dm_block_manager *bm,

			   struct dm_block *superblock);



 /*

  * Request data be prefetched into the cache.

  */

void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);



/*

 * Switches the bm to a read only mode.  Once read-only mode

 * has been entered the following functions will return -EPERM.

drivers/md/persistent-data/dm-btree.c

+21 −5
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ struct frame { 
};



struct del_stack {

	struct dm_btree_info *info;

	struct dm_transaction_manager *tm;

	int top;

	struct frame spine[MAX_SPINE_DEPTH];
@@ -183,6 +184,20 @@ static int unprocessed_frames(struct del_stack *s) 
	return s->top >= 0;

}



static void prefetch_children(struct del_stack *s, struct frame *f)

{

	unsigned i;

	struct dm_block_manager *bm = dm_tm_get_bm(s->tm);



	for (i = 0; i < f->nr_children; i++)

		dm_bm_prefetch(bm, value64(f->n, i));

}



static bool is_internal_level(struct dm_btree_info *info, struct frame *f)

{

	return f->level < (info->levels - 1);

}



static int push_frame(struct del_stack *s, dm_block_t b, unsigned level)

{

	int r;
@@ -205,6 +220,7 @@ static int push_frame(struct del_stack *s, dm_block_t b, unsigned level) 
		dm_tm_dec(s->tm, b);



	else {

		uint32_t flags;

		struct frame *f = s->spine + ++s->top;



		r = dm_tm_read_lock(s->tm, b, &btree_node_validator, &f->b);
@@ -217,6 +233,10 @@ static int push_frame(struct del_stack *s, dm_block_t b, unsigned level) 
		f->level = level;

		f->nr_children = le32_to_cpu(f->n->header.nr_entries);

		f->current_child = 0;



		flags = le32_to_cpu(f->n->header.flags);

		if (flags & INTERNAL_NODE || is_internal_level(s->info, f))

			prefetch_children(s, f);

	}



	return 0;
@@ -230,11 +250,6 @@ static void pop_frame(struct del_stack *s) 
	dm_tm_unlock(s->tm, f->b);

}



static bool is_internal_level(struct dm_btree_info *info, struct frame *f)

{

	return f->level < (info->levels - 1);

}



int dm_btree_del(struct dm_btree_info *info, dm_block_t root)

{

	int r;
@@ -243,6 +258,7 @@ int dm_btree_del(struct dm_btree_info *info, dm_block_t root) 
	s = kmalloc(sizeof(*s), GFP_KERNEL);

	if (!s)

		return -ENOMEM;

	s->info = info;

	s->tm = info->tm;

	s->top = -1;