Commit ac0b74d8 authored by Greg Farnum's avatar Greg Farnum Committed by Sage Weil
Browse files

ceph: add pagelist_reserve, pagelist_truncate, pagelist_set_cursor 



These facilitate preallocation of pages so that we can encode into the pagelist
in an atomic context.

Signed-off-by: default avatarGreg Farnum <gregf@hq.newdream.net>
Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 18a38193

include/linux/ceph/pagelist.h

+21 −0
Original line number Diff line number Diff line
@@ -8,6 +8,14 @@ struct ceph_pagelist { 
	void *mapped_tail;

	size_t length;

	size_t room;

	struct list_head free_list;

	size_t num_pages_free;

};



struct ceph_pagelist_cursor {

	struct ceph_pagelist *pl;   /* pagelist, for error checking */

	struct list_head *page_lru; /* page in list */

	size_t room;		    /* room remaining to reset to */

};



static inline void ceph_pagelist_init(struct ceph_pagelist *pl)
@@ -16,11 +24,24 @@ static inline void ceph_pagelist_init(struct ceph_pagelist *pl) 
	pl->mapped_tail = NULL;

	pl->length = 0;

	pl->room = 0;

	INIT_LIST_HEAD(&pl->free_list);

	pl->num_pages_free = 0;

}



extern int ceph_pagelist_release(struct ceph_pagelist *pl);



extern int ceph_pagelist_append(struct ceph_pagelist *pl, const void *d, size_t l);



extern int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space);



extern int ceph_pagelist_free_reserve(struct ceph_pagelist *pl);



extern void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,

				     struct ceph_pagelist_cursor *c);



extern int ceph_pagelist_truncate(struct ceph_pagelist *pl,

				  struct ceph_pagelist_cursor *c);



static inline int ceph_pagelist_encode_64(struct ceph_pagelist *pl, u64 v)

{

	__le64 ev = cpu_to_le64(v);

net/ceph/pagelist.c

+97 −9
Original line number Diff line number Diff line
@@ -7,35 +7,42 @@ 


static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)

{

	struct page *page = list_entry(pl->head.prev, struct page,

				       lru);

	if (pl->mapped_tail) {

		struct page *page = list_entry(pl->head.prev, struct page, lru);

		kunmap(page);

		pl->mapped_tail = NULL;

	}

}



int ceph_pagelist_release(struct ceph_pagelist *pl)

{

	if (pl->mapped_tail)

	ceph_pagelist_unmap_tail(pl);



	while (!list_empty(&pl->head)) {

		struct page *page = list_first_entry(&pl->head, struct page,

						     lru);

		list_del(&page->lru);

		__free_page(page);

	}

	ceph_pagelist_free_reserve(pl);

	return 0;

}

EXPORT_SYMBOL(ceph_pagelist_release);



static int ceph_pagelist_addpage(struct ceph_pagelist *pl)

{

	struct page *page = __page_cache_alloc(GFP_NOFS);

	struct page *page;



	if (!pl->num_pages_free) {

		page = __page_cache_alloc(GFP_NOFS);

	} else {

		page = list_first_entry(&pl->free_list, struct page, lru);

		list_del(&page->lru);

	}

	if (!page)

		return -ENOMEM;

	pl->room += PAGE_SIZE;

	list_add_tail(&page->lru, &pl->head);

	if (pl->mapped_tail)

	ceph_pagelist_unmap_tail(pl);

	list_add_tail(&page->lru, &pl->head);

	pl->mapped_tail = kmap(page);

	return 0;

}
@@ -63,3 +70,84 @@ int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len) 
	return 0;

}

EXPORT_SYMBOL(ceph_pagelist_append);



/**

 * Allocate enough pages for a pagelist to append the given amount

 * of data without without allocating.

 * Returns: 0 on success, -ENOMEM on error.

 */

int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)

{

	if (space <= pl->room)

		return 0;

	space -= pl->room;

	space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */



	while (space > pl->num_pages_free) {

		struct page *page = __page_cache_alloc(GFP_NOFS);

		if (!page)

			return -ENOMEM;

		list_add_tail(&page->lru, &pl->free_list);

		++pl->num_pages_free;

	}

	return 0;

}

EXPORT_SYMBOL(ceph_pagelist_reserve);



/**

 * Free any pages that have been preallocated.

 */

int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)

{

	while (!list_empty(&pl->free_list)) {

		struct page *page = list_first_entry(&pl->free_list,

						     struct page, lru);

		list_del(&page->lru);

		__free_page(page);

		--pl->num_pages_free;

	}

	BUG_ON(pl->num_pages_free);

	return 0;

}

EXPORT_SYMBOL(ceph_pagelist_free_reserve);



/**

 * Create a truncation point.

 */

void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,

			      struct ceph_pagelist_cursor *c)

{

	c->pl = pl;

	c->page_lru = pl->head.prev;

	c->room = pl->room;

}

EXPORT_SYMBOL(ceph_pagelist_set_cursor);



/**

 * Truncate a pagelist to the given point. Move extra pages to reserve.

 * This won't sleep.

 * Returns: 0 on success,

 *          -EINVAL if the pagelist doesn't match the trunc point pagelist

 */

int ceph_pagelist_truncate(struct ceph_pagelist *pl,

			   struct ceph_pagelist_cursor *c)

{

	struct page *page;



	if (pl != c->pl)

		return -EINVAL;

	ceph_pagelist_unmap_tail(pl);

	while (pl->head.prev != c->page_lru) {

		page = list_entry(pl->head.prev, struct page, lru);

		list_del(&page->lru);                /* remove from pagelist */

		list_add_tail(&page->lru, &pl->free_list); /* add to reserve */

		++pl->num_pages_free;

	}

	pl->room = c->room;

	if (!list_empty(&pl->head)) {

		page = list_entry(pl->head.prev, struct page, lru);

		pl->mapped_tail = kmap(page);

	}

	return 0;

}

EXPORT_SYMBOL(ceph_pagelist_truncate);