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Subject[PATCH -mm] relayfs: support larger relay buffer take 3
Use vmalloc() and memset() instead of kcalloc() to allocate a page* array
when the array size is bigger than one page. This enables relayfs to support
bigger relay buffers than 64MB on 4k-page system, 512MB on 16k-page system.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
---
Changes from take2 to take3:
- Use struct page ** instead of struct page *.
- move functions to the place before relay_mmap_buf.
- add comments.
This is useful for a 64-bit system which has a plenty of memory (tens of
giga bytes) and a large kernel memory space.

I tested it on x86-64 and ia64.

kernel/relay.c | 35 ++++++++++++++++++++++++++++++++---
1 file changed, 32 insertions(+), 3 deletions(-)
Index: 2.6.25-rc8-mm2/kernel/relay.c
===================================================================
--- 2.6.25-rc8-mm2.orig/kernel/relay.c
+++ 2.6.25-rc8-mm2/kernel/relay.c
@@ -65,6 +65,35 @@ static struct vm_operations_struct relay
.close = relay_file_mmap_close,
};

+/*
+ * allocate an array of pointers of struct page
+ */
+static struct page **relay_alloc_page_array(unsigned int n_pages)
+{
+ struct page **array;
+ unsigned int pa_size = n_pages * sizeof(struct page *);
+
+ if (pa_size > PAGE_SIZE) {
+ array = vmalloc(pa_size);
+ if (array)
+ memset(array, 0, pa_size);
+ } else {
+ array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
+ }
+ return array;
+}
+
+/*
+ * free an array of pointers of struct page
+ */
+static void relay_free_page_array(struct page **array)
+{
+ if (is_vmalloc_addr(array))
+ vfree(array);
+ else
+ kfree(array);
+}
+
/**
* relay_mmap_buf: - mmap channel buffer to process address space
* @buf: relay channel buffer
@@ -109,7 +138,7 @@ static void *relay_alloc_buf(struct rcha
*size = PAGE_ALIGN(*size);
n_pages = *size >> PAGE_SHIFT;

- buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
+ buf->page_array = relay_alloc_page_array(n_pages);
if (!buf->page_array)
return NULL;

@@ -130,7 +159,7 @@ static void *relay_alloc_buf(struct rcha
depopulate:
for (j = 0; j < i; j++)
__free_page(buf->page_array[j]);
- kfree(buf->page_array);
+ relay_free_page_array(buf->page_array);
return NULL;
}

@@ -189,7 +218,7 @@ static void relay_destroy_buf(struct rch
vunmap(buf->start);
for (i = 0; i < buf->page_count; i++)
__free_page(buf->page_array[i]);
- kfree(buf->page_array);
+ relay_free_page_array(buf->page_array);
}
chan->buf[buf->cpu] = NULL;
kfree(buf->padding);
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



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