Re: [PATCH] Allow lazy unmapping by taking extra page references V3

David Chinner
2007-10-24T23:21:48Z

On Wed, Oct 24, 2007 at 03:46:16PM -0700, Jeremy Fitzhardinge wrote:
> David Chinner wrote:
> > Version 3:
> > - compile on latest -git
> >
>
> Not quite:
>
> CC mm/vmalloc.o
> /home/jeremy/hg/xen/paravirt/linux/mm/vmalloc.c: In function 'vm_area_alloc_pagearray':
> /home/jeremy/hg/xen/paravirt/linux/mm/vmalloc.c:338: error: 'GFP_LEVEL_MASK' undeclared (first use in this function)
> /home/jeremy/hg/xen/paravirt/linux/mm/vmalloc.c:338: error: (Each undeclared identifier is reported only once
> /home/jeremy/hg/xen/paravirt/linux/mm/vmalloc.c:338: error: for each function it appears in.)
> make[3]: *** [mm/vmalloc.o] Error 1
> make[2]: *** [mm] Error 2
> make[2]: *** Waiting for unfinished jobs....
>
>
> GFP_RECLAM_MASK now?

Yeah, it is. Not sure what happened there - I did make that change.
new diff below.

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index b9c8589..38f073f 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -187,19 +187,6 @@ free_address(
{
a_list_t *aentry;

-#ifdef CONFIG_XEN
- /*
- * Xen needs to be able to make sure it can get an exclusive
- * RO mapping of pages it wants to turn into a pagetable. If
- * a newly allocated page is also still being vmap()ed by xfs,
- * it will cause pagetable construction to fail. This is a
- * quick workaround to always eagerly unmap pages so that Xen
- * is happy.
- */
- vunmap(addr);
- return;
-#endif
-
aentry = kmalloc(sizeof(a_list_t), GFP_NOWAIT);
if (likely(aentry)) {
spin_lock(&as_lock);
@@ -209,7 +196,7 @@ #endif
as_list_len++;
spin_unlock(&as_lock);
} else {
- vunmap(addr);
+ vunmap_pages(addr);
}
}

@@ -228,7 +215,7 @@ purge_addresses(void)
spin_unlock(&as_lock);

while ((old = aentry) != NULL) {
- vunmap(aentry->vm_addr);
+ vunmap_pages(aentry->vm_addr);
aentry = aentry->next;
kfree(old);
}
@@ -458,8 +445,8 @@ _xfs_buf_map_pages(
} else if (flags & XBF_MAPPED) {
if (as_list_len > 64)
purge_addresses();
- bp->b_addr = vmap(bp->b_pages, bp->b_page_count,
- VM_MAP, PAGE_KERNEL);
+ bp->b_addr = vmap_pages(bp->b_pages, bp->b_page_count,
+ VM_MAP, PAGE_KERNEL, xb_to_gfp(flags));
if (unlikely(bp->b_addr == NULL))
return -ENOMEM;
bp->b_addr += bp->b_offset;
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 89338b4..40c34da 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -51,6 +51,10 @@ extern void *vmap(struct page **pages, u
unsigned long flags, pgprot_t prot);
extern void vunmap(void *addr);

+extern void *vmap_pages(struct page **pages, unsigned int count,
+ unsigned long flags, pgprot_t prot, gfp_t gfp_mask);
+extern void vunmap_pages(void *addr);
+
extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
unsigned long pgoff);
void vmalloc_sync_all(void);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index af77e17..720f338 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -319,6 +319,34 @@ struct vm_struct *remove_vm_area(void *a
return v;
}

+static int vm_area_alloc_pagearray(struct vm_struct *area, gfp_t gfp_mask,
+ unsigned int nr_pages, int node)
+{
+ struct page **pages;
+ unsigned int array_size;
+
+ array_size = (nr_pages * sizeof(struct page *));
+
+ area->nr_pages = nr_pages;
+ /* Please note that the recursion is strictly bounded. */
+ if (array_size > PAGE_SIZE) {
+ pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
+ PAGE_KERNEL, node);
+ area->flags |= VM_VPAGES;
+ } else {
+ pages = kmalloc_node(array_size,
+ (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
+ node);
+ }
+ area->pages = pages;
+ if (!area->pages) {
+ remove_vm_area(area->addr);
+ kfree(area);
+ return -ENOMEM;
+ }
+ return 0;
+}
+
static void __vunmap(void *addr, int deallocate_pages)
{
struct vm_struct *area;
@@ -347,7 +375,7 @@ static void __vunmap(void *addr, int dea

for (i = 0; i < area->nr_pages; i++) {
BUG_ON(!area->pages[i]);
- __free_page(area->pages[i]);
+ put_page(area->pages[i]);
}

if (area->flags & VM_VPAGES)
@@ -394,6 +422,23 @@ void vunmap(void *addr)
EXPORT_SYMBOL(vunmap);

/**
+ * vunmap_pages - release virtual mapping obtained by vmap_pages()
+ * @addr: memory base address
+ *
+ * Free the virtually contiguous memory area starting at @addr,
+ * which was created from the page array passed to vmap_pages(),
+ * releasing the reference on the pages gained in vmap_pages().
+ *
+ * Must not be called in interrupt context.
+ */
+void vunmap_pages(void *addr)
+{
+ BUG_ON(in_interrupt());
+ __vunmap(addr, 1);
+}
+EXPORT_SYMBOL(vunmap_pages);
+
+/**
* vmap - map an array of pages into virtually contiguous space
* @pages: array of page pointers
* @count: number of pages to map
@@ -423,32 +468,63 @@ void *vmap(struct page **pages, unsigned
}
EXPORT_SYMBOL(vmap);

+/**
+ * vmap_pages - map an array of pages into virtually contiguous space
+ * @pages: array of page pointers
+ * @count: number of pages to map
+ * @flags: vm_area->flags
+ * @prot: page protection for the mapping
+ * @gfp_mask: flags for the page level allocator
+ *
+ * Maps @count pages from @pages into contiguous kernel virtual
+ * space taking a reference to each page and keeping track of all
+ * the pages within the vm area structure.
+ */
+void *vmap_pages(struct page **pages, unsigned int count,
+ unsigned long flags, pgprot_t prot, gfp_t gfp_mask)
+{
+ struct vm_struct *area;
+ struct page **pgp;
+ int i;
+
+ if (count > num_physpages)
+ return NULL;
+
+ area = get_vm_area((count << PAGE_SHIFT), flags);
+ if (!area)
+ return NULL;
+ if (vm_area_alloc_pagearray(area, gfp_mask, count, -1))
+ return NULL;
+
+ /* map_vm_area modifies pgp */
+ pgp = pages;
+ if (map_vm_area(area, prot, &pgp)) {
+ vunmap(area->addr);
+ return NULL;
+ }
+ /*
+ * now that the region is mapped, take a reference to each
+ * page and store them in the area page array.
+ */
+ for (i = 0; i < area->nr_pages; i++) {
+ get_page(pages[i]);
+ area->pages[i] = pages[i];
+ }
+
+ return area->addr;
+}
+EXPORT_SYMBOL(vmap_pages);
+
void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
pgprot_t prot, int node)
{
struct page **pages;
- unsigned int nr_pages, array_size, i;
+ unsigned int nr_pages;
+ int i;

nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT;
- array_size = (nr_pages * sizeof(struct page *));
-
- area->nr_pages = nr_pages;
- /* Please note that the recursion is strictly bounded. */
- if (array_size > PAGE_SIZE) {
- pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
- PAGE_KERNEL, node);
- area->flags |= VM_VPAGES;
- } else {
- pages = kmalloc_node(array_size,
- (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
- node);
- }
- area->pages = pages;
- if (!area->pages) {
- remove_vm_area(area->addr);
- kfree(area);
+ if (vm_area_alloc_pagearray(area, gfp_mask, nr_pages, node))
return NULL;
- }

for (i = 0; i < area->nr_pages; i++) {
if (node < 0)
@@ -462,6 +538,8 @@ void *__vmalloc_area_node(struct vm_stru
}
}

+ /* map_vm_area modifies pages */
+ pages = area->pages;
if (map_vm_area(area, prot, &pages))
goto fail;
return area->addr;