[Xen-devel] [PATCH] linux: fix blkback/blktap2 interaction

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

blkback's page map code needs to be accessible to both blkback and
blktap2, irrespective of whether either or both are modules. The
most immediate solution is to break it out into a separate, library-
like component that doesn't need building if either of the two
consumers is configured off, and that gets built as a module if both
consumers are modules.

Also fix the dummy implementation of blkback_pagemap_read(), since
using BUG() there doesn't compile.

This patch will only apply cleanly on top of the previously sent patch
allowing blktap2 to build as a module.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- head-2009-05-29.orig/drivers/xen/Kconfig    2009-06-03 16:12:43.000000000 
+0200
+++ head-2009-05-29/drivers/xen/Kconfig 2009-06-03 10:26:22.000000000 +0200
@@ -76,6 +76,11 @@ config XEN_BLKDEV_TAP2
           as files, in memory, or on other hosts across the network.  This 
          driver can safely coexist with the existing blockback driver.
 
+config XEN_BLKBACK_PAGEMAP
+       tristate
+       depends on XEN_BLKDEV_BACKEND != n && XEN_BLKDEV_TAP2 != n
+       default XEN_BLKDEV_BACKEND || XEN_BLKDEV_TAP2
+
 config XEN_NETDEV_BACKEND
        tristate "Network-device backend driver"
         depends on XEN_BACKEND && NET
--- head-2009-05-29.orig/drivers/xen/blkback/Makefile   2009-06-03 
16:12:43.000000000 +0200
+++ head-2009-05-29/drivers/xen/blkback/Makefile        2009-06-03 
09:50:42.000000000 +0200
@@ -1,3 +1,4 @@
 obj-$(CONFIG_XEN_BLKDEV_BACKEND) := blkbk.o
+obj-$(CONFIG_XEN_BLKBACK_PAGEMAP) += blkback-pagemap.o
 
-blkbk-y        := blkback.o xenbus.o interface.o vbd.o blkback-pagemap.o
+blkbk-y        := blkback.o xenbus.o interface.o vbd.o
--- head-2009-05-29.orig/drivers/xen/blkback/blkback-pagemap.c  2009-06-03 
16:12:43.000000000 +0200
+++ head-2009-05-29/drivers/xen/blkback/blkback-pagemap.c       2009-06-03 
16:02:40.000000000 +0200
@@ -1,4 +1,4 @@
-#include "common.h"
+#include <linux/module.h>
 #include "blkback-pagemap.h"
 
 static int blkback_pagemap_size;
@@ -22,6 +22,7 @@ blkback_pagemap_init(int pages)
        blkback_pagemap_size = pages;
        return 0;
 }
+EXPORT_SYMBOL_GPL(blkback_pagemap_init);
 
 void
 blkback_pagemap_set(int idx, struct page *page,
@@ -46,6 +47,7 @@ blkback_pagemap_set(int idx, struct page
        entry->busid = busid;
        entry->gref  = gref;
 }
+EXPORT_SYMBOL_GPL(blkback_pagemap_set);
 
 void
 blkback_pagemap_clear(struct page *page)
@@ -67,6 +69,7 @@ blkback_pagemap_clear(struct page *page)
 
        memset(entry, 0, sizeof(*entry));
 }
+EXPORT_SYMBOL_GPL(blkback_pagemap_clear);
 
 struct blkback_pagemap
 blkback_pagemap_read(struct page *page)
@@ -89,3 +92,5 @@ blkback_pagemap_read(struct page *page)
        return *entry;
 }
 EXPORT_SYMBOL(blkback_pagemap_read);
+
+MODULE_LICENSE("Dual BSD/GPL");
--- head-2009-05-29.orig/drivers/xen/blkback/blkback-pagemap.h  2009-06-03 
16:12:43.000000000 +0200
+++ head-2009-05-29/drivers/xen/blkback/blkback-pagemap.h       2009-06-03 
16:13:17.000000000 +0200
@@ -1,6 +1,7 @@
 #ifndef _BLKBACK_PAGEMAP_H_
 #define _BLKBACK_PAGEMAP_H_
 
+#include <linux/mm.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/grant_table.h>
 
@@ -12,6 +13,25 @@ struct blkback_pagemap {
        grant_ref_t      gref;
 };
 
+#if defined(CONFIG_XEN_BLKBACK_PAGEMAP) || 
defined(CONFIG_XEN_BLKBACK_PAGEMAP_MODULE)
+
+int blkback_pagemap_init(int);
+void blkback_pagemap_set(int, struct page *, domid_t, busid_t, grant_ref_t);
+void blkback_pagemap_clear(struct page *);
 struct blkback_pagemap blkback_pagemap_read(struct page *);
 
+#else /* CONFIG_XEN_BLKBACK_PAGEMAP */
+
+static inline int blkback_pagemap_init(int pages) { return 0; }
+static inline void blkback_pagemap_set(int idx, struct page *page, domid_t dom,
+                                      busid_t bus, grant_ref_t gnt) {}
+static inline void blkback_pagemap_clear(struct page *page) {}
+static inline struct blkback_pagemap blkback_pagemap_read(struct page *page)
+{
+       BUG();
+       return (struct blkback_pagemap){-1, -1, -1};
+}
+
+#endif /* CONFIG_XEN_BLKBACK_PAGEMAP */
+
 #endif
--- head-2009-05-29.orig/drivers/xen/blkback/common.h   2009-06-03 
16:12:43.000000000 +0200
+++ head-2009-05-29/drivers/xen/blkback/common.h        2009-06-03 
09:55:06.000000000 +0200
@@ -150,8 +150,4 @@ int blkif_schedule(void *arg);
 int blkback_barrier(struct xenbus_transaction xbt,
                    struct backend_info *be, int state);
 
-int blkback_pagemap_init(int);
-void blkback_pagemap_set(int, struct page *, domid_t, busid_t, grant_ref_t);
-void blkback_pagemap_clear(struct page *);
-
 #endif /* __BLKIF__BACKEND__COMMON_H__ */
--- head-2009-05-29.orig/drivers/xen/blktap2/device.c   2009-06-03 
16:12:43.000000000 +0200
+++ head-2009-05-29/drivers/xen/blktap2/device.c        2009-06-03 
15:40:39.000000000 +0200
@@ -14,13 +14,7 @@
 
 #include "blktap.h"
 
-#if defined(CONFIG_XEN_BLKDEV_BACKEND) || \
-    (defined(CONFIG_XEN_BLKDEV_BACKEND_MODULE) && defined(MODULE))
 #include "../blkback/blkback-pagemap.h"
-#else
-struct blkback_pagemap { };
-#define blkback_pagemap_read(page) BUG();
-#endif
 
 #if 0
 #define DPRINTK_IOCTL(_f, _a...) printk(KERN_ALERT _f, ## _a)



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