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Message-Id: <1588812129-8596-3-git-send-email-anthony.yznaga@oracle.com>
Date: Wed, 6 May 2020 17:41:28 -0700
From: Anthony Yznaga <anthony.yznaga@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: willy@...radead.org, corbet@....net, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
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Subject: [RFC 02/43] mm: PKRAM: implement node load and save functions
Preserved memory is divided into nodes which can be saved and loaded
independently of each other. PKRAM nodes are kept on a list and
identified by unique names. Whenever a save operation is initiated by
calling pkram_prepare_save(), a new node is created and linked to the
list. When the save operation has been committed by calling
pkram_finish_save(), the node becomes loadable. A load operation can be
then initiated by calling pkram_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 pkram_finish_load()
function must be called to free the node. Nodes are also deleted when a
save operation is discarded, i.e. pkram_discard_save() is called instead
of pkram_finish_save().
Originally-by: Vladimir Davydov <vdavydov.dev@...il.com>
Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
include/linux/pkram.h | 7 ++-
mm/pkram.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 149 insertions(+), 6 deletions(-)
diff --git a/include/linux/pkram.h b/include/linux/pkram.h
index 4c4e13311ec8..83a0579e4c1c 100644
--- a/include/linux/pkram.h
+++ b/include/linux/pkram.h
@@ -6,7 +6,12 @@
#include <linux/types.h>
#include <linux/mm_types.h>
-struct pkram_stream;
+struct pkram_node;
+
+struct pkram_stream {
+ gfp_t gfp_mask;
+ struct pkram_node *node;
+};
#define PKRAM_NAME_MAX 256 /* including nul */
diff --git a/mm/pkram.c b/mm/pkram.c
index d6f2f79d4852..5c57126353ff 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -2,16 +2,85 @@
#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/pkram.h>
+#include <linux/string.h>
#include <linux/types.h>
+/*
+ * Preserved 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 pkram_node {
+ __u32 flags;
+
+ __u8 name[PKRAM_NAME_MAX];
+};
+
+#define PKRAM_SAVE 1
+#define PKRAM_LOAD 2
+#define PKRAM_ACCMODE_MASK 3
+
+static LIST_HEAD(pkram_nodes); /* linked through page::lru */
+static DEFINE_MUTEX(pkram_mutex); /* serializes open/close */
+
+static inline struct page *pkram_alloc_page(gfp_t gfp_mask)
+{
+ return alloc_page(gfp_mask);
+}
+
+static inline void pkram_free_page(void *addr)
+{
+ free_page((unsigned long)addr);
+}
+
+static inline void pkram_insert_node(struct pkram_node *node)
+{
+ list_add(&virt_to_page(node)->lru, &pkram_nodes);
+}
+
+static inline void pkram_delete_node(struct pkram_node *node)
+{
+ list_del(&virt_to_page(node)->lru);
+}
+
+static struct pkram_node *pkram_find_node(const char *name)
+{
+ struct page *page;
+ struct pkram_node *node;
+
+ list_for_each_entry(page, &pkram_nodes, lru) {
+ node = page_address(page);
+ if (strcmp(node->name, name) == 0)
+ return node;
+ }
+ return NULL;
+}
+
+static void pkram_stream_init(struct pkram_stream *ps,
+ struct pkram_node *node, gfp_t gfp_mask)
+{
+ memset(ps, 0, sizeof(*ps));
+ ps->gfp_mask = gfp_mask;
+ ps->node = node;
+}
+
/**
* Create a preserved memory node with name @name and initialize stream @ps
* for saving data to it.
*
* @gfp_mask specifies the memory allocation mask to be used when saving data.
*
+ * Error values:
+ * %ENAMETOOLONG: name len >= PKRAM_NAME_MAX
+ * %ENOMEM: insufficient memory available
+ * %EEXIST: node with specified name already exists
+ *
* Returns 0 on success, -errno on failure.
*
* After the save has finished, pkram_finish_save() (or pkram_discard_save() in
@@ -19,7 +88,34 @@
*/
int pkram_prepare_save(struct pkram_stream *ps, const char *name, gfp_t gfp_mask)
{
- return -ENOSYS;
+ struct page *page;
+ struct pkram_node *node;
+ int err = 0;
+
+ if (strlen(name) >= PKRAM_NAME_MAX)
+ return -ENAMETOOLONG;
+
+ page = pkram_alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+ node = page_address(page);
+
+ node->flags = PKRAM_SAVE;
+ strcpy(node->name, name);
+
+ mutex_lock(&pkram_mutex);
+ if (!pkram_find_node(name))
+ pkram_insert_node(node);
+ else
+ err = -EEXIST;
+ mutex_unlock(&pkram_mutex);
+ if (err) {
+ __free_page(page);
+ return err;
+ }
+
+ pkram_stream_init(ps, node, gfp_mask);
+ return 0;
}
/**
@@ -50,7 +146,12 @@ void pkram_finish_save_obj(struct pkram_stream *ps)
*/
void pkram_finish_save(struct pkram_stream *ps)
{
- BUG();
+ struct pkram_node *node = ps->node;
+
+ BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
+
+ smp_wmb();
+ node->flags &= ~PKRAM_ACCMODE_MASK;
}
/**
@@ -60,7 +161,15 @@ void pkram_finish_save(struct pkram_stream *ps)
*/
void pkram_discard_save(struct pkram_stream *ps)
{
- BUG();
+ struct pkram_node *node = ps->node;
+
+ BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
+
+ mutex_lock(&pkram_mutex);
+ pkram_delete_node(node);
+ mutex_unlock(&pkram_mutex);
+
+ pkram_free_page(node);
}
/**
@@ -69,11 +178,36 @@ void pkram_discard_save(struct pkram_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
+ *
* After the load has finished, pkram_finish_load() is to be called.
*/
int pkram_prepare_load(struct pkram_stream *ps, const char *name)
{
- return -ENOSYS;
+ struct pkram_node *node;
+ int err = 0;
+
+ mutex_lock(&pkram_mutex);
+ node = pkram_find_node(name);
+ if (!node) {
+ err = -ENOENT;
+ goto out_unlock;
+ }
+ if (node->flags & PKRAM_ACCMODE_MASK) {
+ err = -EBUSY;
+ goto out_unlock;
+ }
+ pkram_delete_node(node);
+out_unlock:
+ mutex_unlock(&pkram_mutex);
+ if (err)
+ return err;
+
+ node->flags |= PKRAM_LOAD;
+ pkram_stream_init(ps, node, 0);
+ return 0;
}
/**
@@ -106,7 +240,11 @@ void pkram_finish_load_obj(struct pkram_stream *ps)
*/
void pkram_finish_load(struct pkram_stream *ps)
{
- BUG();
+ struct pkram_node *node = ps->node;
+
+ BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_LOAD);
+
+ pkram_free_page(node);
}
/**
--
2.13.3
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