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authorGreg Farnum <gregf@hq.newdream.net>2010-09-17 10:10:55 -0700
committerSage Weil <sage@newdream.net>2010-10-20 15:38:16 -0700
commitac0b74d8a1ced8ea86147467daf06b15b130dd94 (patch)
treea71aec65be7f71b42ae78907acd5b0f4aeafd3a9
parent18a38193efcaac1fb3c94ad8fa04bb117850a3c2 (diff)
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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: Greg Farnum <gregf@hq.newdream.net> Signed-off-by: Sage Weil <sage@newdream.net>
-rw-r--r--include/linux/ceph/pagelist.h21
-rw-r--r--net/ceph/pagelist.c106
2 files changed, 118 insertions, 9 deletions
diff --git a/include/linux/ceph/pagelist.h b/include/linux/ceph/pagelist.h
index cc9327aa1c9..9660d6b0a35 100644
--- a/include/linux/ceph/pagelist.h
+++ b/include/linux/ceph/pagelist.h
@@ -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);
diff --git a/net/ceph/pagelist.c b/net/ceph/pagelist.c
index 3b146cfac18..b8cbc456d0b 100644
--- a/net/ceph/pagelist.c
+++ b/net/ceph/pagelist.c
@@ -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);
- kunmap(page);
+ 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);
-
+ 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;
+ ceph_pagelist_unmap_tail(pl);
list_add_tail(&page->lru, &pl->head);
- if (pl->mapped_tail)
- ceph_pagelist_unmap_tail(pl);
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);