[Xen-changelog] [linux-2.6.18-xen] Remove xencomm page size limit.

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1188311595 -3600
# Node ID 7419a3be82737bc2de83749030759e104c92e1ea
# Parent  b5fdf02c38f4765697196f5fad5d1262f2c157f4
Remove xencomm page size limit.

Currently xencomm has page size limit so that a domain with many
memory (e.g. 100GB~) can't be created.

Now that xencomm of xen side accepts struct xencomm_desc whose address
array crosses page boundary. Thus it isn't necessary to allocate
single page not to cross page boundary. We can allocate exact sized
memory. Note that struct xencomm_desc can't cross page boundary and
slab allocator returns sizeof(void*) aligned pointer.
Where sizeof(*desc) > sizeof(void*), e.g. 32 bit environment,
the slab allocator return pointer doesn't gurantee that
struct xencomm_desc doesn't cross page boundary. So we fall back to
page allocator.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
 drivers/xen/core/xencomm.c |   57 +++++++++++++++++++++++++++++++++------------
 1 files changed, 43 insertions(+), 14 deletions(-)

diff -r b5fdf02c38f4 -r 7419a3be8273 drivers/xen/core/xencomm.c
--- a/drivers/xen/core/xencomm.c        Thu Aug 16 13:44:51 2007 -0600
+++ b/drivers/xen/core/xencomm.c        Tue Aug 28 15:33:15 2007 +0100
@@ -68,25 +68,54 @@ static int xencomm_init(struct xencomm_d
        return 0;
 }
 
-/* XXX use slab allocator */
-static struct xencomm_desc *xencomm_alloc(gfp_t gfp_mask)
-{
-       struct xencomm_desc *desc;
-
-       desc = (struct xencomm_desc *)__get_free_page(gfp_mask);
-       if (desc == NULL)
-               return NULL;
-
-       desc->nr_addrs = (PAGE_SIZE - sizeof(struct xencomm_desc)) /
+static struct xencomm_desc *xencomm_alloc(gfp_t gfp_mask,
+                                         void *buffer, unsigned long bytes)
+{
+       struct xencomm_desc *desc;
+       unsigned long buffer_ulong = (unsigned long)buffer;
+       unsigned long start = buffer_ulong & PAGE_MASK;
+       unsigned long end = (buffer_ulong + bytes) | ~PAGE_MASK;
+       unsigned long nr_addrs = (end - start + 1) >> PAGE_SHIFT;
+       unsigned long size = sizeof(*desc) +
+               sizeof(desc->address[0]) * nr_addrs;
+
+       /*
+        * slab allocator returns at least sizeof(void*) aligned pointer.
+        * When sizeof(*desc) > sizeof(void*), struct xencomm_desc might
+        * cross page boundary.
+        */
+       if (sizeof(*desc) > sizeof(void*)) {
+               unsigned long order = get_order(size);
+               desc = (struct xencomm_desc *)__get_free_pages(gfp_mask,
+                                                              order);
+               if (desc == NULL)
+                       return NULL;
+
+               desc->nr_addrs =
+                       ((PAGE_SIZE << order) - sizeof(struct xencomm_desc)) /
                        sizeof(*desc->address);
-
+       } else {
+               desc = kmalloc(size, gfp_mask);
+               if (desc == NULL)
+                       return NULL;
+
+               desc->nr_addrs = nr_addrs;
+       }
        return desc;
 }
 
 void xencomm_free(struct xencomm_handle *desc)
 {
-       if (desc && !((ulong)desc & XENCOMM_INLINE_FLAG))
-               free_page((unsigned long)__va(desc));
+       if (desc && !((ulong)desc & XENCOMM_INLINE_FLAG)) {
+               struct xencomm_desc *desc__ = (struct xencomm_desc*)desc;
+               if (sizeof(*desc__) > sizeof(void*)) {
+                       unsigned long size = sizeof(*desc__) +
+                               sizeof(desc__->address[0]) * desc__->nr_addrs;
+                       unsigned long order = get_order(size);
+                       free_pages((unsigned long)__va(desc), order);
+               } else
+                       kfree(__va(desc));
+       }
 }
 
 static int xencomm_create(void *buffer, unsigned long bytes, struct 
xencomm_desc **ret, gfp_t gfp_mask)
@@ -105,7 +134,7 @@ static int xencomm_create(void *buffer, 
 
        BUG_ON(buffer == NULL); /* 'bytes' is non-zero */
 
-       desc = xencomm_alloc(gfp_mask);
+       desc = xencomm_alloc(gfp_mask, buffer, bytes);
        if (!desc) {
                printk("%s failure\n", "xencomm_alloc");
                return -ENOMEM;

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