Persistent memory is divided into nodes, which can be saved and loaded
independently of each other. PRAM nodes are kept on the list and
identified by unique names. Whenever a save operation is initiated by
calling pram_prepare_save(), a new node is created and linked to the
list. When the save operation has been committed by calling
pram_finish_save(), the node becomes loadable. A load operation can be
then initiated by calling pram_prepare_load(), which deletes the node
from the list and prepares the corresponding stream for loading data
from it. After the load has been finished, the pram_finish_load()
function must be called to free the node. Nodes are also deleted when a
save operation is discarded, i.e. pram_discard_save() is called instead
of pram_finish_save().
---
include/linux/pram.h | 7 ++-
mm/pram.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 159 insertions(+), 6 deletions(-)
diff --git a/include/linux/pram.h b/include/linux/pram.h
index cf04548..5b8c2c1 100644
--- a/include/linux/pram.h
+++ b/include/linux/pram.h
@@ -5,7 +5,12 @@
#include <linux/types.h>
#include <linux/mm_types.h>
-struct pram_stream;
+struct pram_node;
+
+struct pram_stream {
+ gfp_t gfp_mask;
+ struct pram_node *node;
+};
#define PRAM_NAME_MAX 256 /* including nul */
diff --git a/mm/pram.c b/mm/pram.c
index cea0e87..3af2039 100644
--- a/mm/pram.c
+++ b/mm/pram.c
@@ -1,10 +1,75 @@
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
+#include <linux/list.h>
#include <linux/mm.h>
+#include <linux/mutex.h>
#include <linux/pram.h>
+#include <linux/string.h>
#include <linux/types.h>
+/*
+ * Persistent memory is divided into nodes that can be saved or loaded
+ * independently of each other. The nodes are identified by unique name
+ * strings.
+ *
+ * The structure occupies a memory page.
+ */
+struct pram_node {
+ __u32 flags; /* see PRAM_* flags below */
+ __u32 type; /* data type, see enum pram_stream_type */
+
+ __u8 name[PRAM_NAME_MAX];
+};
+
+#define PRAM_SAVE 1
+#define PRAM_LOAD 2
+#define PRAM_ACCMODE_MASK 3
+
+static LIST_HEAD(pram_nodes); /* linked through page::lru */
+static DEFINE_MUTEX(pram_mutex); /* serializes open/close */
+
+static inline struct page *pram_alloc_page(gfp_t gfp_mask)
+{
+ return alloc_page(gfp_mask);
+}
+
+static inline void pram_free_page(void *addr)
+{
+ free_page((unsigned long)addr);
+}
+
+static inline void pram_insert_node(struct pram_node *node)
+{
+ list_add(&virt_to_page(node)->lru, &pram_nodes);
+}
+
+static inline void pram_delete_node(struct pram_node *node)
+{
+ list_del(&virt_to_page(node)->lru);
+}
+
+static struct pram_node *pram_find_node(const char *name)
+{
+ struct page *page;
+ struct pram_node *node;
+
+ list_for_each_entry(page, &pram_nodes, lru) {
+ node = page_address(page);
+ if (strcmp(node->name, name) == 0)
+ return node;
+ }
+ return NULL;
+}
+
+static void pram_stream_init(struct pram_stream *ps,
+ struct pram_node *node, gfp_t gfp_mask)
+{
+ memset(ps, 0, sizeof(*ps));
+ ps->gfp_mask = gfp_mask;
+ ps->node = node;
+}
+
/**
* Create a persistent memory node with name @name and initialize stream @ps
* for saving data to it.
@@ -18,13 +83,49 @@
*
* Returns 0 on success, -errno on failure.
*
+ * Error values:
+ * %ENAMETOOLONG: name len >= PRAM_NAME_MAX
+ * %ENOMEM: insufficient memory available
+ * %EEXIST: node with specified name already exists
+ *
* After the save has finished, pram_finish_save() (or pram_discard_save() in
* case of failure) is to be called.
*/
int pram_prepare_save(struct pram_stream *ps,
const char *name, enum pram_stream_type type, gfp_t gfp_mask)
{
- return -ENOSYS;
+ struct page *page;
+ struct pram_node *node;
+ int err = 0;
+
+ BUG_ON(type != PRAM_PAGE_STREAM &&
+ type != PRAM_BYTE_STREAM);
+
+ if (strlen(name) >= PRAM_NAME_MAX)
+ return -ENAMETOOLONG;
+
+ page = pram_alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+ node = page_address(page);
+
+ node->flags = PRAM_SAVE;
+ node->type = type;
+ strcpy(node->name, name);
+
+ mutex_lock(&pram_mutex);
+ if (!pram_find_node(name))
+ pram_insert_node(node);
+ else
+ err = -EEXIST;
+ mutex_unlock(&pram_mutex);
+ if (err) {
+ __free_page(page);
+ return err;
+ }
+
+ pram_stream_init(ps, node, gfp_mask);
+ return 0;
}
/**
@@ -33,7 +134,12 @@ int pram_prepare_save(struct pram_stream *ps,
*/
void pram_finish_save(struct pram_stream *ps)
{
- BUG();
+ struct pram_node *node = ps->node;
+
+ BUG_ON((node->flags & PRAM_ACCMODE_MASK) != PRAM_SAVE);
+
+ smp_wmb();
+ node->flags &= ~PRAM_ACCMODE_MASK;
}
/**
@@ -43,7 +149,15 @@ void pram_finish_save(struct pram_stream *ps)
*/
void pram_discard_save(struct pram_stream *ps)
{
- BUG();
+ struct pram_node *node = ps->node;
+
+ BUG_ON((node->flags & PRAM_ACCMODE_MASK) != PRAM_SAVE);
+
+ mutex_lock(&pram_mutex);
+ pram_delete_node(node);
+ mutex_unlock(&pram_mutex);
+
+ pram_free_page(node);
}
/**
@@ -57,12 +171,42 @@ void pram_discard_save(struct pram_stream *ps)
*
* Returns 0 on success, -errno on failure.
*
+ * Error values:
+ * %ENOENT: node with specified name does not exist
+ * %EBUSY: save to required node has not finished yet
+ * %EPERM: specified type conflicts with type of required node
+ *
* After the load has finished, pram_finish_load() is to be called.
*/
int pram_prepare_load(struct pram_stream *ps,
const char *name, enum pram_stream_type type)
{
- return -ENOSYS;
+ struct pram_node *node;
+ int err = 0;
+
+ mutex_lock(&pram_mutex);
+ node = pram_find_node(name);
+ if (!node) {
+ err = -ENOENT;
+ goto out_unlock;
+ }
+ if (node->flags & PRAM_ACCMODE_MASK) {
+ err = -EBUSY;
+ goto out_unlock;
+ }
+ if (node->type != type) {
+ err = -EPERM;
+ goto out_unlock;
+ }
+ pram_delete_node(node);
+out_unlock:
+ mutex_unlock(&pram_mutex);
+ if (err)
+ return err;
+
+ node->flags |= PRAM_LOAD;
+ pram_stream_init(ps, node, 0);
+ return 0;
}
/**
@@ -72,7 +216,11 @@ int pram_prepare_load(struct pram_stream *ps,
*/
void pram_finish_load(struct pram_stream *ps)
{
- BUG();
+ struct pram_node *node = ps->node;
+
+ BUG_ON((node->flags & PRAM_ACCMODE_MASK) != PRAM_LOAD);
+
+ pram_free_page(node);
}
/**
--
1.7.10.4
--
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