xen: cleancache shim to Xen Transcendent Memory

This patch provides a shim between the kernel-internal cleancache
API (see Documentation/mm/cleancache.txt) and the Xen Transcendent
Memory ABI (see http://oss.oracle.com/projects/tmem).

Xen tmem provides "hypervisor RAM" as an ephemeral page-oriented
pseudo-RAM store for cleancache pages, shared cleancache pages,
and frontswap pages.  Tmem provides enterprise-quality concurrency,
full save/restore and live migration support, compression
and deduplication.

A presentation showing up to 8% faster performance and up to 52%
reduction in sectors read on a kernel compile workload, despite
aggressive in-kernel page reclamation ("self-ballooning") can be
found at:

http://oss.oracle.com/projects/tmem/dist/documentation/presentations/TranscendentMemoryXenSummit2010.pdf

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik Van Riel <riel@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Andreas Dilger <adilger@sun.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Nitin Gupta <ngupta@vflare.org>

2 files changed, 265 insertions, 0 deletions

diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index f420f1ff7f13..7aa6804173ab 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -1,5 +1,6 @@
 obj-y   += grant-table.o features.o events.o manage.o balloon.o
 obj-y   += xenbus/
+obj-y   += tmem.o
 
 nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_features.o                       := $(nostackp)
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
new file mode 100644
index 000000000000..816a44959ef0
--- /dev/null
+++ b/drivers/xen/tmem.c
@@ -0,0 +1,264 @@
+/*
+ * Xen implementation for transcendent memory (tmem)
+ *
+ * Copyright (C) 2009-2010 Oracle Corp.  All rights reserved.
+ * Author: Dan Magenheimer
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/cleancache.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+#include <asm/xen/hypervisor.h>
+
+#define TMEM_CONTROL               0
+#define TMEM_NEW_POOL              1
+#define TMEM_DESTROY_POOL          2
+#define TMEM_NEW_PAGE              3
+#define TMEM_PUT_PAGE              4
+#define TMEM_GET_PAGE              5
+#define TMEM_FLUSH_PAGE            6
+#define TMEM_FLUSH_OBJECT          7
+#define TMEM_READ                  8
+#define TMEM_WRITE                 9
+#define TMEM_XCHG                 10
+
+/* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
+#define TMEM_POOL_PERSIST          1
+#define TMEM_POOL_SHARED           2
+#define TMEM_POOL_PAGESIZE_SHIFT   4
+#define TMEM_VERSION_SHIFT        24
+
+
+struct tmem_pool_uuid {
+        u64 uuid_lo;
+        u64 uuid_hi;
+};
+
+struct tmem_oid {
+        u64 oid[3];
+};
+
+#define TMEM_POOL_PRIVATE_UUID  { 0, 0 }
+
+/* flags for tmem_ops.new_pool */
+#define TMEM_POOL_PERSIST          1
+#define TMEM_POOL_SHARED           2
+
+/* xen tmem foundation ops/hypercalls */
+
+static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
+        u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
+{
+        struct tmem_op op;
+        int rc = 0;
+
+        op.cmd = tmem_cmd;
+        op.pool_id = tmem_pool;
+        op.u.gen.oid[0] = oid.oid[0];
+        op.u.gen.oid[1] = oid.oid[1];
+        op.u.gen.oid[2] = oid.oid[2];
+        op.u.gen.index = index;
+        op.u.gen.tmem_offset = tmem_offset;
+        op.u.gen.pfn_offset = pfn_offset;
+        op.u.gen.len = len;
+        set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
+        rc = HYPERVISOR_tmem_op(&op);
+        return rc;
+}
+
+static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
+                                u32 flags, unsigned long pagesize)
+{
+        struct tmem_op op;
+        int rc = 0, pageshift;
+
+        for (pageshift = 0; pagesize != 1; pageshift++)
+                pagesize >>= 1;
+        flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
+        flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
+        op.cmd = TMEM_NEW_POOL;
+        op.u.new.uuid[0] = uuid.uuid_lo;
+        op.u.new.uuid[1] = uuid.uuid_hi;
+        op.u.new.flags = flags;
+        rc = HYPERVISOR_tmem_op(&op);
+        return rc;
+}
+
+/* xen generic tmem ops */
+
+static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
+                             u32 index, unsigned long pfn)
+{
+        unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+        return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
+                gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
+                             u32 index, unsigned long pfn)
+{
+        unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+        return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
+                gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
+{
+        return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
+                0, 0, 0, 0);
+}
+
+static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
+{
+        return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+static int xen_tmem_destroy_pool(u32 pool_id)
+{
+        struct tmem_oid oid = { { 0 } };
+
+        return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+int tmem_enabled;
+
+static int __init enable_tmem(char *s)
+{
+        tmem_enabled = 1;
+        return 1;
+}
+
+__setup("tmem", enable_tmem);
+
+/* cleancache ops */
+
+static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
+                                     pgoff_t index, struct page *page)
+{
+        u32 ind = (u32) index;
+        struct tmem_oid oid = *(struct tmem_oid *)&key;
+        unsigned long pfn = page_to_pfn(page);
+
+        if (pool < 0)
+                return;
+        if (ind != index)
+                return;
+        mb(); /* ensure page is quiescent; tmem may address it with an alias */
+        (void)xen_tmem_put_page((u32)pool, oid, ind, pfn);
+}
+
+static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
+                                    pgoff_t index, struct page *page)
+{
+        u32 ind = (u32) index;
+        struct tmem_oid oid = *(struct tmem_oid *)&key;
+        unsigned long pfn = page_to_pfn(page);
+        int ret;
+
+        /* translate return values to linux semantics */
+        if (pool < 0)
+                return -1;
+        if (ind != index)
+                return -1;
+        ret = xen_tmem_get_page((u32)pool, oid, ind, pfn);
+        if (ret == 1)
+                return 0;
+        else
+                return -1;
+}
+
+static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
+                                       pgoff_t index)
+{
+        u32 ind = (u32) index;
+        struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+        if (pool < 0)
+                return;
+        if (ind != index)
+                return;
+        (void)xen_tmem_flush_page((u32)pool, oid, ind);
+}
+
+static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
+{
+        struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+        if (pool < 0)
+                return;
+        (void)xen_tmem_flush_object((u32)pool, oid);
+}
+
+static void tmem_cleancache_flush_fs(int pool)
+{
+        if (pool < 0)
+                return;
+        (void)xen_tmem_destroy_pool((u32)pool);
+}
+
+static int tmem_cleancache_init_fs(size_t pagesize)
+{
+        struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;
+
+        return xen_tmem_new_pool(uuid_private, 0, pagesize);
+}
+
+static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+        struct tmem_pool_uuid shared_uuid;
+
+        shared_uuid.uuid_lo = *(u64 *)uuid;
+        shared_uuid.uuid_hi = *(u64 *)(&uuid[8]);
+        return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
+}
+
+static int use_cleancache = 1;
+
+static int __init no_cleancache(char *s)
+{
+        use_cleancache = 0;
+        return 1;
+}
+
+__setup("nocleancache", no_cleancache);
+
+static struct cleancache_ops tmem_cleancache_ops = {
+        .put_page = tmem_cleancache_put_page,
+        .get_page = tmem_cleancache_get_page,
+        .flush_page = tmem_cleancache_flush_page,
+        .flush_inode = tmem_cleancache_flush_inode,
+        .flush_fs = tmem_cleancache_flush_fs,
+        .init_shared_fs = tmem_cleancache_init_shared_fs,
+        .init_fs = tmem_cleancache_init_fs
+};
+
+static int __init xen_tmem_init(void)
+{
+        struct cleancache_ops old_ops;
+
+        if (!xen_domain())
+                return 0;
+#ifdef CONFIG_CLEANCACHE
+        BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
+        if (tmem_enabled && use_cleancache) {
+                char *s = "";
+                old_ops = cleancache_register_ops(&tmem_cleancache_ops);
+                if (old_ops.init_fs != NULL)
+                        s = " (WARNING: cleancache_ops overridden)";
+                printk(KERN_INFO "cleancache enabled, RAM provided by "
+                                 "Xen Transcendent Memory%s\n", s);
+        }
+#endif
+        return 0;
+}
+
+module_init(xen_tmem_init)