Using the pkram_save_file_page() function, one can populate PKRAM objects
with in-memory pages which can later be loaded using the pkram_load_file_page()
function. Saving a page to PKRAM is accomplished by recording its pfn and
mapping index and incrementing its refcount so that it will not be freed
after the last user puts it.
Originally-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
---
include/linux/pkram.h | 42 +++++++-
mm/pkram.c | 282 +++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 317 insertions(+), 7 deletions(-)
diff --git a/include/linux/pkram.h b/include/linux/pkram.h
index a4d55af392c0..9d8a6fd96dd9 100644
--- a/include/linux/pkram.h
+++ b/include/linux/pkram.h
@@ -8,22 +8,47 @@
struct pkram_node;
struct pkram_obj;
+struct pkram_link;
/**
* enum pkram_data_flags - definition of data types contained in a pkram obj
* @PKRAM_DATA_none: No data types configured
+ * @PKRAM_DATA_pages: obj contains file page data
*/
enum pkram_data_flags {
- PKRAM_DATA_none = 0x0, /* No data types configured */
+ PKRAM_DATA_none = 0x0, /* No data types configured */
+ PKRAM_DATA_pages = 0x1, /* Contains file page data */
+};
+
+struct pkram_data_stream {
+ /* List of link pages to add/remove from */
+ __u64 *head_link_pfnp;
+ __u64 *tail_link_pfnp;
+
+ struct pkram_link *link; /* current link */
+ unsigned int entry_idx; /* next entry in link */
};
struct pkram_stream {
gfp_t gfp_mask;
struct pkram_node *node;
struct pkram_obj *obj;
+
+ __u64 *pages_head_link_pfnp;
+ __u64 *pages_tail_link_pfnp;
+};
+
+struct pkram_pages_access {
+ unsigned long next_index;
};
-struct pkram_access;
+struct pkram_access {
+ enum pkram_data_flags dtype;
+ struct pkram_stream *ps;
+ struct pkram_data_stream pds;
+
+ struct pkram_pages_access pages;
+};
#define PKRAM_NAME_MAX 256 /* including nul */
@@ -41,8 +66,19 @@ int pkram_prepare_save(struct pkram_stream *ps, const char *name,
void pkram_finish_load(struct pkram_stream *ps);
void pkram_finish_load_obj(struct pkram_stream *ps);
+#define PKRAM_PDS_INIT(name, stream, type) { \
+ .head_link_pfnp=(stream)->type##_head_link_pfnp, \
+ .tail_link_pfnp=(stream)->type##_tail_link_pfnp, \
+ }
+
+#define PKRAM_ACCESS_INIT(name, stream, type) { \
+ .dtype = PKRAM_DATA_##type, \
+ .ps = (stream), \
+ .pds = PKRAM_PDS_INIT(name, stream, type), \
+ }
+
#define PKRAM_ACCESS(name, stream, type) \
- struct pkram_access name
+ struct pkram_access name = PKRAM_ACCESS_INIT(name, stream, type)
void pkram_finish_access(struct pkram_access *pa, bool status_ok);
diff --git a/mm/pkram.c b/mm/pkram.c
index 7c977c5982f8..9c42db66d022 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/err.h>
#include <linux/gfp.h>
+#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
@@ -10,8 +11,39 @@
#include <linux/string.h>
#include <linux/types.h>
+#include "internal.h"
+
+
+/*
+ * Represents a reference to a data page saved to PKRAM.
+ */
+typedef __u64 pkram_entry_t;
+
+#define PKRAM_ENTRY_FLAGS_SHIFT 0x5
+#define PKRAM_ENTRY_FLAGS_MASK 0x7f
+
+/*
+ * Keeps references to data pages saved to PKRAM.
+ * The structure occupies a memory page.
+ */
+struct pkram_link {
+ __u64 link_pfn; /* points to the next link of the object */
+ __u64 index; /* mapping index of first pkram_entry_t */
+
+ /*
+ * the array occupies the rest of the link page; if the link is not
+ * full, the rest of the array must be filled with zeros
+ */
+ pkram_entry_t entry[0];
+};
+
+#define PKRAM_LINK_ENTRIES_MAX \
+ ((PAGE_SIZE-sizeof(struct pkram_link))/sizeof(pkram_entry_t))
+
struct pkram_obj {
- __u64 obj_pfn; /* points to the next object in the list */
+ __u64 pages_head_link_pfn; /* the first pages link of the object */
+ __u64 pages_tail_link_pfn; /* the last pages link of the object */
+ __u64 obj_pfn; /* points to the next object in the list */
};
/*
@@ -19,6 +51,10 @@ struct pkram_obj {
* independently of each other. The nodes are identified by unique name
* strings.
*
+ * References to data pages saved to a preserved memory node are kept in a
+ * singly-linked list of PKRAM link structures (see above), the node has a
+ * pointer to the head of.
+ *
* The structure occupies a memory page.
*/
struct pkram_node {
@@ -68,6 +104,41 @@ static struct pkram_node *pkram_find_node(const char *name)
return NULL;
}
+static void pkram_truncate_link(struct pkram_link *link)
+{
+ struct page *page;
+ pkram_entry_t p;
+ int i;
+
+ for (i = 0; i < PKRAM_LINK_ENTRIES_MAX; i++) {
+ p = link->entry[i];
+ if (!p)
+ continue;
+ page = pfn_to_page(PHYS_PFN(p));
+ put_page(page);
+ }
+}
+
+static void pkram_truncate_links(unsigned long link_pfn)
+{
+ struct pkram_link *link;
+
+ while (link_pfn) {
+ link = pfn_to_kaddr(link_pfn);
+ pkram_truncate_link(link);
+ link_pfn = link->link_pfn;
+ pkram_free_page(link);
+ cond_resched();
+ }
+}
+
+static void pkram_truncate_obj(struct pkram_obj *obj)
+{
+ pkram_truncate_links(obj->pages_head_link_pfn);
+ obj->pages_head_link_pfn = 0;
+ obj->pages_tail_link_pfn = 0;
+}
+
static void pkram_truncate_node(struct pkram_node *node)
{
unsigned long obj_pfn;
@@ -76,6 +147,7 @@ static void pkram_truncate_node(struct pkram_node *node)
obj_pfn = node->obj_pfn;
while (obj_pfn) {
obj = pfn_to_kaddr(obj_pfn);
+ pkram_truncate_obj(obj);
obj_pfn = obj->obj_pfn;
pkram_free_page(obj);
cond_resched();
@@ -83,6 +155,83 @@ static void pkram_truncate_node(struct pkram_node *node)
node->obj_pfn = 0;
}
+static void pkram_add_link(struct pkram_link *link, struct pkram_data_stream *pds)
+{
+ __u64 link_pfn = page_to_pfn(virt_to_page(link));
+
+ if (!*pds->head_link_pfnp) {
+ *pds->head_link_pfnp = link_pfn;
+ *pds->tail_link_pfnp = link_pfn;
+ } else {
+ struct pkram_link *tail = pfn_to_kaddr(*pds->tail_link_pfnp);
+
+ tail->link_pfn = link_pfn;
+ *pds->tail_link_pfnp = link_pfn;
+ }
+}
+
+static struct pkram_link *pkram_remove_link(struct pkram_data_stream *pds)
+{
+ struct pkram_link *link;
+
+ if (!*pds->head_link_pfnp)
+ return NULL;
+
+ link = pfn_to_kaddr(*pds->head_link_pfnp);
+ *pds->head_link_pfnp = link->link_pfn;
+ if (!*pds->head_link_pfnp)
+ *pds->tail_link_pfnp = 0;
+ else
+ link->link_pfn = 0;
+
+ return link;
+}
+
+static struct pkram_link *pkram_new_link(struct pkram_data_stream *pds, gfp_t gfp_mask)
+{
+ struct pkram_link *link;
+ struct page *link_page;
+
+ link_page = pkram_alloc_page((gfp_mask & GFP_RECLAIM_MASK) |
+ __GFP_ZERO);
+ if (!link_page)
+ return NULL;
+
+ link = page_address(link_page);
+ pkram_add_link(link, pds);
+ pds->link = link;
+ pds->entry_idx = 0;
+
+ return link;
+}
+
+static void pkram_add_link_entry(struct pkram_data_stream *pds, struct page *page)
+{
+ struct pkram_link *link = pds->link;
+ pkram_entry_t p;
+ short flags = 0;
+
+ p = page_to_phys(page);
+ p |= ((flags & PKRAM_ENTRY_FLAGS_MASK) << PKRAM_ENTRY_FLAGS_SHIFT);
+ link->entry[pds->entry_idx] = p;
+ pds->entry_idx++;
+}
+
+static int pkram_next_link(struct pkram_data_stream *pds, struct pkram_link **linkp)
+{
+ struct pkram_link *link;
+
+ link = pkram_remove_link(pds);
+ if (!link)
+ return -ENODATA;
+
+ pds->link = link;
+ pds->entry_idx = 0;
+ *linkp = link;
+
+ return 0;
+}
+
static void pkram_stream_init(struct pkram_stream *ps,
struct pkram_node *node, gfp_t gfp_mask)
{
@@ -159,6 +308,9 @@ int pkram_prepare_save_obj(struct pkram_stream *ps, enum pkram_data_flags flags)
BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
+ if (flags & ~PKRAM_DATA_pages)
+ return -EINVAL;
+
page = pkram_alloc_page(ps->gfp_mask | __GFP_ZERO);
if (!page)
return -ENOMEM;
@@ -168,6 +320,10 @@ int pkram_prepare_save_obj(struct pkram_stream *ps, enum pkram_data_flags flags)
obj->obj_pfn = node->obj_pfn;
node->obj_pfn = page_to_pfn(page);
+ if (flags & PKRAM_DATA_pages) {
+ ps->pages_head_link_pfnp = &obj->pages_head_link_pfn;
+ ps->pages_tail_link_pfnp = &obj->pages_tail_link_pfn;
+ }
ps->obj = obj;
return 0;
}
@@ -275,8 +431,17 @@ int pkram_prepare_load_obj(struct pkram_stream *ps)
return -ENODATA;
obj = pfn_to_kaddr(node->obj_pfn);
+ if (!obj->pages_head_link_pfn) {
+ WARN_ON(1);
+ return -EINVAL;
+ }
+
node->obj_pfn = obj->obj_pfn;
+ if (obj->pages_head_link_pfn) {
+ ps->pages_head_link_pfnp = &obj->pages_head_link_pfn;
+ ps->pages_tail_link_pfnp = &obj->pages_tail_link_pfn;
+ }
ps->obj = obj;
return 0;
}
@@ -293,6 +458,7 @@ void pkram_finish_load_obj(struct pkram_stream *ps)
BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_LOAD);
+ pkram_truncate_obj(obj);
pkram_free_page(obj);
}
@@ -318,7 +484,41 @@ void pkram_finish_load(struct pkram_stream *ps)
*/
void pkram_finish_access(struct pkram_access *pa, bool status_ok)
{
- BUG();
+ if (status_ok)
+ return;
+
+ if (pa->ps->node->flags == PKRAM_SAVE)
+ return;
+
+ if (pa->pds.link)
+ pkram_truncate_link(pa->pds.link);
+}
+
+/*
+ * Add file page to a PKRAM obj allocating a new PKRAM link if necessary.
+ */
+static int __pkram_save_page(struct pkram_access *pa, struct page *page,
+ unsigned long index)
+{
+ struct pkram_data_stream *pds = &pa->pds;
+ struct pkram_link *link = pds->link;
+
+ if (!link || pds->entry_idx >= PKRAM_LINK_ENTRIES_MAX ||
+ index != pa->pages.next_index) {
+ link = pkram_new_link(pds, pa->ps->gfp_mask);
+ if (!link)
+ return -ENOMEM;
+
+ pa->pages.next_index = link->index = index;
+ }
+
+ get_page(page);
+
+ pkram_add_link_entry(pds, page);
+
+ pa->pages.next_index++;
+
+ return 0;
}
/**
@@ -328,10 +528,80 @@ void pkram_finish_access(struct pkram_access *pa, bool status_ok)
* with PKRAM_ACCESS().
*
* Returns 0 on success, -errno on failure.
+ *
+ * Error values:
+ * %ENOMEM: insufficient amount of memory available
+ *
+ * Saving a page to preserved memory is simply incrementing its refcount so
+ * that it will not get freed after the last user puts it. That means it is
+ * safe to use the page as usual after it has been saved.
*/
int pkram_save_file_page(struct pkram_access *pa, struct page *page)
{
- return -ENOSYS;
+ struct pkram_node *node = pa->ps->node;
+
+ BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
+
+ BUG_ON(PageCompound(page));
+
+ return __pkram_save_page(pa, page, page->index);
+}
+
+static struct page *__pkram_prep_load_page(pkram_entry_t p)
+{
+ struct page *page;
+ short flags;
+
+ flags = (p >> PKRAM_ENTRY_FLAGS_SHIFT) & PKRAM_ENTRY_FLAGS_MASK;
+ page = pfn_to_page(PHYS_PFN(p));
+
+ return page;
+}
+
+/*
+ * Extract the next page from preserved memory freeing a PKRAM link if it
+ * becomes empty.
+ */
+static struct page *__pkram_load_page(struct pkram_access *pa, unsigned long *index)
+{
+ struct pkram_data_stream *pds = &pa->pds;
+ struct pkram_link *link = pds->link;
+ struct page *page;
+ pkram_entry_t p;
+ int ret;
+
+ if (!link) {
+ ret = pkram_next_link(pds, &link);
+ if (ret)
+ return NULL; // XXX return error value?
+
+ if (index)
+ pa->pages.next_index = link->index;
+ }
+
+ BUG_ON(pds->entry_idx >= PKRAM_LINK_ENTRIES_MAX);
+
+ p = link->entry[pds->entry_idx];
+ BUG_ON(!p);
+
+ page = __pkram_prep_load_page(p);
+
+ if (index) {
+ *index = pa->pages.next_index;
+ pa->pages.next_index++;
+ }
+
+ /* clear to avoid double free (see pkram_truncate_link()) */
+ link->entry[pds->entry_idx] = 0;
+
+ pds->entry_idx++;
+ if (pds->entry_idx >= PKRAM_LINK_ENTRIES_MAX ||
+ !link->entry[pds->entry_idx]) {
+ pds->link = NULL;
+ pkram_free_page(link);
+ }
+
+ return page;
}
/**
@@ -349,7 +619,11 @@ int pkram_save_file_page(struct pkram_access *pa, struct page *page)
*/
struct page *pkram_load_file_page(struct pkram_access *pa, unsigned long *index)
{
- return NULL;
+ struct pkram_node *node = pa->ps->node;
+
+ BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_LOAD);
+
+ return __pkram_load_page(pa, index);
}
/**
--
1.8.3.1
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