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From: Anthony Yznaga <anthony.yznaga@oracle.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: willy@infradead.org, corbet@lwn.net, tglx@linutronix.de,
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	kexec@lists.infradead.org
Subject: [RFC 02/43] mm: PKRAM: implement node load and save functions
Date: Wed,  6 May 2020 17:41:28 -0700	[thread overview]
Message-ID: <1588812129-8596-3-git-send-email-anthony.yznaga@oracle.com> (raw)
In-Reply-To: <1588812129-8596-1-git-send-email-anthony.yznaga@oracle.com>

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@gmail.com>
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.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


  parent reply	other threads:[~2020-05-07  0:45 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-07  0:41 [RFC 00/43] PKRAM: Preserved-over-Kexec RAM Anthony Yznaga
2020-05-07  0:41 ` [RFC 01/43] mm: add PKRAM API stubs and Kconfig Anthony Yznaga
2020-05-07  0:41 ` Anthony Yznaga [this message]
2020-05-07  0:41 ` [RFC 03/43] mm: PKRAM: implement object load and save functions Anthony Yznaga
2020-05-07  0:41 ` [RFC 04/43] mm: PKRAM: implement page stream operations Anthony Yznaga
2020-05-07  0:41 ` [RFC 05/43] mm: PKRAM: support preserving transparent hugepages Anthony Yznaga
2020-05-07  0:41 ` [RFC 06/43] mm: PKRAM: implement byte stream operations Anthony Yznaga
2020-05-07  0:41 ` [RFC 07/43] mm: PKRAM: link nodes by pfn before reboot Anthony Yznaga
2020-05-07  0:41 ` [RFC 08/43] mm: PKRAM: introduce super block Anthony Yznaga
2020-05-07  0:41 ` [RFC 09/43] PKRAM: build a physical mapping pagetable of pages to be preserved Anthony Yznaga
2020-05-07  0:41 ` [RFC 10/43] PKRAM: add code for walking the preserved pages pagetable Anthony Yznaga
2020-05-07  0:41 ` [RFC 11/43] PKRAM: pass the preserved pages pagetable to the next kernel Anthony Yznaga
2020-05-07  0:41 ` [RFC 12/43] mm: PKRAM: reserve preserved memory at boot Anthony Yznaga
2020-05-07  0:41 ` [RFC 13/43] mm: PKRAM: free preserved pages pagetable Anthony Yznaga
2020-05-07  0:41 ` [RFC 14/43] mm: memblock: PKRAM: prevent memblock resize from clobbering preserved pages Anthony Yznaga
2020-05-11 13:57   ` Mike Rapoport
2020-05-11 23:29     ` Anthony Yznaga
2020-05-07  0:41 ` [RFC 15/43] PKRAM: provide a way to ban pages from use by PKRAM Anthony Yznaga
2020-05-07  0:41 ` [RFC 16/43] kexec: PKRAM: prevent kexec clobbering preserved pages in some cases Anthony Yznaga
2020-05-07  0:41 ` [RFC 17/43] PKRAM: provide a way to check if a memory range has preserved pages Anthony Yznaga
2020-05-07  0:41 ` [RFC 18/43] kexec: PKRAM: avoid clobbering already " Anthony Yznaga
2020-05-07  0:41 ` [RFC 19/43] mm: PKRAM: allow preserved memory to be freed from userspace Anthony Yznaga
2020-05-07  0:41 ` [RFC 20/43] PKRAM: disable feature when running the kdump kernel Anthony Yznaga
2020-05-07  0:41 ` [RFC 21/43] x86/KASLR: PKRAM: support physical kaslr Anthony Yznaga
2020-05-07 17:51   ` Kees Cook
2020-05-07 18:41     ` Anthony Yznaga
2020-05-07  0:41 ` [RFC 22/43] mm: shmem: introduce shmem_insert_page Anthony Yznaga
2020-05-07  0:41 ` [RFC 23/43] mm: shmem: enable saving to PKRAM Anthony Yznaga
2020-05-07  0:41 ` [RFC 24/43] mm: shmem: prevent swapping of PKRAM-enabled tmpfs pages Anthony Yznaga
2020-05-07  0:41 ` [RFC 25/43] mm: shmem: specify the mm to use when inserting pages Anthony Yznaga
2020-05-07  0:41 ` [RFC 26/43] mm: shmem: when inserting, handle pages already charged to a memcg Anthony Yznaga
2020-05-07  0:41 ` [RFC 27/43] x86/mm/numa: add numa_isolate_memblocks() Anthony Yznaga
2020-05-07  0:41 ` [RFC 28/43] PKRAM: ensure memblocks with preserved pages init'd for numa Anthony Yznaga
2020-05-07  0:41 ` [RFC 29/43] memblock: PKRAM: mark memblocks that contain preserved pages Anthony Yznaga
2020-05-07  0:41 ` [RFC 30/43] memblock: add for_each_reserved_mem_range() Anthony Yznaga
2020-05-07  0:41 ` [RFC 31/43] memblock, mm: defer initialization of preserved pages Anthony Yznaga
2020-05-07  0:41 ` [RFC 32/43] shmem: PKRAM: preserve shmem files a chunk at a time Anthony Yznaga
2020-05-07  0:41 ` [RFC 33/43] PKRAM: atomically add and remove link pages Anthony Yznaga
2020-05-07  0:42 ` [RFC 34/43] shmem: PKRAM: multithread preserving and restoring shmem pages Anthony Yznaga
2020-05-07 16:30   ` Randy Dunlap
2020-05-07 17:59     ` Anthony Yznaga
2020-05-07  0:42 ` [RFC 35/43] shmem: introduce shmem_insert_pages() Anthony Yznaga
2020-05-07  0:42 ` [RFC 36/43] PKRAM: add support for loading pages in bulk Anthony Yznaga
2020-05-07  0:42 ` [RFC 37/43] shmem: PKRAM: enable bulk loading of preserved pages into shmem Anthony Yznaga
2020-05-07  0:42 ` [RFC 38/43] mm: implement splicing a list of pages to the LRU Anthony Yznaga
2020-05-07  0:42 ` [RFC 39/43] shmem: optimize adding pages to the LRU in shmem_insert_pages() Anthony Yznaga
2020-05-07  0:42 ` [RFC 40/43] shmem: initial support for adding multiple pages to pagecache Anthony Yznaga
2020-05-07  0:42 ` [RFC 41/43] XArray: add xas_export_node() and xas_import_node() Anthony Yznaga
2020-05-07  0:42 ` [RFC 42/43] shmem: reduce time holding xa_lock when inserting pages Anthony Yznaga
2020-05-07  0:42 ` [RFC 43/43] PKRAM: improve index alignment of pkram_link entries Anthony Yznaga

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