From 3624e43282b0c6aad32829f116fd8f7bce66fbb6 Mon Sep 17 00:00:00 2001
From: Thomas Hellstrom <thomas-at-tungstengraphics-dot-com>
Date: Fri, 20 Oct 2006 15:06:31 +0200
Subject: Bug #8707, 2.6.19-rc compatibility for memory manager code.

---
 linux-core/drm_compat.c | 53 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 20 deletions(-)

(limited to 'linux-core/drm_compat.c')

diff --git a/linux-core/drm_compat.c b/linux-core/drm_compat.c
index 90e53419..b466f8bd 100644
--- a/linux-core/drm_compat.c
+++ b/linux-core/drm_compat.c
@@ -28,6 +28,11 @@
 #include "drmP.h"
 
 #if defined(CONFIG_X86) && (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
+
+/*
+ * These have bad performance in the AGP module for the indicated kernel versions.
+ */
+
 int drm_map_page_into_agp(struct page *page)
 {
         int i;
@@ -45,8 +50,14 @@ int drm_unmap_page_from_agp(struct page *page)
          * performance reasons */
         return i;
 }
-#endif
+#endif 
+
 
+#if  (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19))
+
+/*
+ * The protection map was exported in 2.6.19
+ */
 
 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 {
@@ -62,8 +73,17 @@ pgprot_t vm_get_page_prot(unsigned long vm_flags)
 	return protection_map[vm_flags & 0x0F];
 #endif
 };
+#endif
 
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19))
+
+#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
+
+/*
+ * vm code for kernels below 2,6,15 in which version a major vm write
+ * occured. This implement a simple straightforward 
+ * version similar to what's going to be
+ * in kernel 2.6.20+?
+ */ 
 
 static int drm_pte_is_clear(struct vm_area_struct *vma,
 			    unsigned long addr)
@@ -76,12 +96,7 @@ static int drm_pte_is_clear(struct vm_area_struct *vma,
 	pgd_t *pgd;
 	
 
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
 	spin_lock(&mm->page_table_lock);
-#else
-	spinlock_t *ptl;
-#endif
-	
 	pgd = pgd_offset(mm, addr);
 	if (pgd_none(*pgd))
 		goto unlock;
@@ -91,22 +106,13 @@ static int drm_pte_is_clear(struct vm_area_struct *vma,
 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		goto unlock;
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
 	pte = pte_offset_map(pmd, addr);
-#else 
-	pte = pte_offset_map_lock(mm, pmd, addr, &ptl); 
-#endif
 	if (!pte)
 		goto unlock;
 	ret = pte_none(*pte);
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
 	pte_unmap(pte);
  unlock:	
 	spin_unlock(&mm->page_table_lock);
-#else
-	pte_unmap_unlock(pte, ptl);
- unlock:
-#endif
 	return ret;
 }
 	
@@ -121,7 +127,6 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-
 static struct {
 	spinlock_t lock;
 	struct page *dummy_page;
@@ -154,9 +159,6 @@ void free_nopage_retry(void)
 		spin_unlock(&drm_np_retry.lock);
 	}
 }
-#endif
-
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15))
 
 struct page *drm_vm_ttm_nopage(struct vm_area_struct *vma,
 			       unsigned long address, 
@@ -186,6 +188,17 @@ struct page *drm_vm_ttm_nopage(struct vm_area_struct *vma,
 
 #ifdef DRM_ODD_MM_COMPAT
 
+/*
+ * VM compatibility code for 2.6.15-2.6.19(?). This code implements a complicated
+ * workaround for a single BUG statement in do_no_page in these versions. The
+ * tricky thing is that we need to take the mmap_sem in exclusive mode for _all_
+ * vmas mapping the ttm, before dev->struct_mutex is taken. The way we do this is to 
+ * check first take the dev->struct_mutex, and then trylock all mmap_sems. If this
+ * fails for a single mmap_sem, we have to release all sems and the dev->struct_mutex,
+ * release the cpu and retry. We also need to keep track of all vmas mapping the ttm.
+ * phew.
+ */
+
 typedef struct p_mm_entry {
 	struct list_head head;
 	struct mm_struct *mm;
-- 
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