Stress testing revealed the need for (yet more) revision. sorry.
This is a revision of Andrew's mspec-handle-shrinking-virtual-memory-areas.patch
Version 4: clear/release fetchop pages only when vma_data is no longer shared
The vma_data structure may be shared by vma's from multiple tasks, with
no way of knowing which areas are shared or not shared, so release/clear
pages only when the refcount (of vma's) goes to zero.
Diffed against 2.6.23-rc7
Signed-off-by: Cliff Wickman <[email protected]>
---
drivers/char/mspec.c | 26 ++++++++------------------
1 file changed, 8 insertions(+), 18 deletions(-)
Index: linus.070920/drivers/char/mspec.c
===================================================================
--- linus.070920.orig/drivers/char/mspec.c
+++ linus.070920/drivers/char/mspec.c
@@ -155,23 +155,22 @@ mspec_open(struct vm_area_struct *vma)
* mspec_close
*
* Called when unmapping a device mapping. Frees all mspec pages
- * belonging to the vma.
+ * belonging to all the vma's sharing this vma_data structure.
*/
static void
mspec_close(struct vm_area_struct *vma)
{
struct vma_data *vdata;
- int index, last_index, result;
+ int index, last_index;
unsigned long my_page;
vdata = vma->vm_private_data;
- BUG_ON(vma->vm_start < vdata->vm_start || vma->vm_end > vdata->vm_end);
+ if (!atomic_dec_and_test(&vdata->refcnt))
+ return;
- spin_lock(&vdata->lock);
- index = (vma->vm_start - vdata->vm_start) >> PAGE_SHIFT;
- last_index = (vma->vm_end - vdata->vm_start) >> PAGE_SHIFT;
- for (; index < last_index; index++) {
+ last_index = (vdata->vm_end - vdata->vm_start) >> PAGE_SHIFT;
+ for (index=0; index < last_index; index++) {
if (vdata->maddr[index] == 0)
continue;
/*
@@ -180,20 +179,12 @@ mspec_close(struct vm_area_struct *vma)
*/
my_page = vdata->maddr[index];
vdata->maddr[index] = 0;
- spin_unlock(&vdata->lock);
- result = mspec_zero_block(my_page, PAGE_SIZE);
- if (!result)
+ if (!mspec_zero_block(my_page, PAGE_SIZE))
uncached_free_page(my_page);
else
printk(KERN_WARNING "mspec_close(): "
- "failed to zero page %i\n",
- result);
- spin_lock(&vdata->lock);
+ "failed to zero page %ld\n", my_page);
}
- spin_unlock(&vdata->lock);
-
- if (!atomic_dec_and_test(&vdata->refcnt))
- return;
if (vdata->flags & VMD_VMALLOCED)
vfree(vdata);
@@ -201,7 +192,6 @@ mspec_close(struct vm_area_struct *vma)
kfree(vdata);
}
-
/*
* mspec_nopfn
*
-
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