From: Hugh Dickins <hugh@veritas.com>
arm and parisc __flush_dcache_page have been scanning the i_mmap(_shared) list
without locking or disabling preemption. That may be even more unsafe now
it's a prio tree instead of a list.
It looks like we cannot use i_shared_lock for this protection: most uses of
flush_dcache_page are okay, and only one would need lock ordering fixed
(get_user_pages holds page_table_lock across flush_dcache_page); but there's a
few (e.g. in net and ntfs) which look as if they're using it in I/O
completion - and it would be restrictive to disallow it there.
So, on arm and parisc only, define flush_dcache_mmap_lock(mapping) as
spin_lock_irq(&(mapping)->tree_lock); on i386 (and other arches left to the
next patch) define it away to nothing; and use where needed.
While updating locking hierarchy in filemap.c, remove two layers of the fossil
record from add_to_page_cache comment: no longer used for swap.
I believe all the #includes will work out, but have only built i386. I can
see several things about this patch which might cause revulsion: the name
flush_dcache_mmap_lock? the reuse of the page radix_tree's tree_lock for this
different purpose? spin_lock_irqsave instead? can't we somehow get
i_shared_lock to handle the problem?
---
25-akpm/arch/arm/mm/fault-armv.c | 5 +++++
25-akpm/arch/parisc/kernel/cache.c | 2 ++
25-akpm/include/asm-arm/cacheflush.h | 5 +++++
25-akpm/include/asm-i386/cacheflush.h | 2 ++
25-akpm/include/asm-parisc/cacheflush.h | 5 +++++
25-akpm/kernel/fork.c | 2 ++
25-akpm/mm/filemap.c | 4 +++-
25-akpm/mm/fremap.c | 2 ++
25-akpm/mm/mmap.c | 10 +++++++++-
9 files changed, 35 insertions(+), 2 deletions(-)
diff -puN arch/arm/mm/fault-armv.c~rmap-22-flush_dcache_mmap_lock arch/arm/mm/fault-armv.c
--- 25/arch/arm/mm/fault-armv.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/arch/arm/mm/fault-armv.c Tue May 4 17:52:28 2004
@@ -94,6 +94,8 @@ void __flush_dcache_page(struct page *pa
* and invalidate any user data.
*/
pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+
+ flush_dcache_mmap_lock(mapping);
while ((mpnt = vma_prio_tree_next(mpnt, &mapping->i_mmap,
&iter, pgoff, pgoff)) != NULL) {
/*
@@ -106,6 +108,7 @@ void __flush_dcache_page(struct page *pa
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
flush_cache_page(mpnt, mpnt->vm_start + offset);
}
+ flush_dcache_mmap_unlock(mapping);
}
static void
@@ -129,6 +132,7 @@ make_coherent(struct vm_area_struct *vma
* space, then we need to handle them specially to maintain
* cache coherency.
*/
+ flush_dcache_mmap_lock(mapping);
while ((mpnt = vma_prio_tree_next(mpnt, &mapping->i_mmap,
&iter, pgoff, pgoff)) != NULL) {
/*
@@ -143,6 +147,7 @@ make_coherent(struct vm_area_struct *vma
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
aliases += adjust_pte(mpnt, mpnt->vm_start + offset);
}
+ flush_dcache_mmap_unlock(mapping);
if (aliases)
adjust_pte(vma, addr);
else
diff -puN arch/parisc/kernel/cache.c~rmap-22-flush_dcache_mmap_lock arch/parisc/kernel/cache.c
--- 25/arch/parisc/kernel/cache.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/arch/parisc/kernel/cache.c Tue May 4 17:52:28 2004
@@ -244,6 +244,7 @@ void __flush_dcache_page(struct page *pa
pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ flush_dcache_mmap_lock(mapping);
while ((mpnt = vma_prio_tree_next(mpnt, &mapping->i_mmap,
&iter, pgoff, pgoff)) != NULL) {
/*
@@ -262,6 +263,7 @@ void __flush_dcache_page(struct page *pa
*/
break;
}
+ flush_dcache_mmap_unlock(mapping);
}
EXPORT_SYMBOL(__flush_dcache_page);
diff -puN include/asm-arm/cacheflush.h~rmap-22-flush_dcache_mmap_lock include/asm-arm/cacheflush.h
--- 25/include/asm-arm/cacheflush.h~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/include/asm-arm/cacheflush.h Tue May 4 17:52:28 2004
@@ -303,6 +303,11 @@ static inline void flush_dcache_page(str
__flush_dcache_page(page);
}
+#define flush_dcache_mmap_lock(mapping) \
+ spin_lock_irq(&(mapping)->tree_lock)
+#define flush_dcache_mmap_unlock(mapping) \
+ spin_unlock_irq(&(mapping)->tree_lock)
+
#define flush_icache_user_range(vma,page,addr,len) \
flush_dcache_page(page)
diff -puN include/asm-i386/cacheflush.h~rmap-22-flush_dcache_mmap_lock include/asm-i386/cacheflush.h
--- 25/include/asm-i386/cacheflush.h~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/include/asm-i386/cacheflush.h Tue May 4 17:52:28 2004
@@ -10,6 +10,8 @@
#define flush_cache_range(vma, start, end) do { } while (0)
#define flush_cache_page(vma, vmaddr) do { } while (0)
#define flush_dcache_page(page) do { } while (0)
+#define flush_dcache_mmap_lock(mapping) do { } while (0)
+#define flush_dcache_mmap_unlock(mapping) do { } while (0)
#define flush_icache_range(start, end) do { } while (0)
#define flush_icache_page(vma,pg) do { } while (0)
#define flush_icache_user_range(vma,pg,adr,len) do { } while (0)
diff -puN include/asm-parisc/cacheflush.h~rmap-22-flush_dcache_mmap_lock include/asm-parisc/cacheflush.h
--- 25/include/asm-parisc/cacheflush.h~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/include/asm-parisc/cacheflush.h Tue May 4 17:52:28 2004
@@ -78,6 +78,11 @@ static inline void flush_dcache_page(str
}
}
+#define flush_dcache_mmap_lock(mapping) \
+ spin_lock_irq(&(mapping)->tree_lock)
+#define flush_dcache_mmap_unlock(mapping) \
+ spin_unlock_irq(&(mapping)->tree_lock)
+
#define flush_icache_page(vma,page) do { flush_kernel_dcache_page(page_address(page)); flush_kernel_icache_page(page_address(page)); } while (0)
#define flush_icache_range(s,e) do { flush_kernel_dcache_range_asm(s,e); flush_kernel_icache_range_asm(s,e); } while (0)
diff -puN kernel/fork.c~rmap-22-flush_dcache_mmap_lock kernel/fork.c
--- 25/kernel/fork.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/kernel/fork.c Tue May 4 17:52:28 2004
@@ -331,7 +331,9 @@ static inline int dup_mmap(struct mm_str
/* insert tmp into the share list, just after mpnt */
spin_lock(&file->f_mapping->i_shared_lock);
+ flush_dcache_mmap_lock(mapping);
vma_prio_tree_add(tmp, mpnt);
+ flush_dcache_mmap_unlock(mapping);
spin_unlock(&file->f_mapping->i_shared_lock);
}
diff -puN mm/filemap.c~rmap-22-flush_dcache_mmap_lock mm/filemap.c
--- 25/mm/filemap.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/mm/filemap.c Tue May 4 17:52:28 2004
@@ -65,7 +65,9 @@
* ->i_shared_lock (truncate->unmap_mapping_range)
*
* ->mmap_sem
- * ->i_shared_lock (various places)
+ * ->i_shared_lock
+ * ->page_table_lock (various places, mainly in mmap.c)
+ * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
*
* ->mmap_sem
* ->lock_page (access_process_vm)
diff -puN mm/fremap.c~rmap-22-flush_dcache_mmap_lock mm/fremap.c
--- 25/mm/fremap.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/mm/fremap.c Tue May 4 17:52:28 2004
@@ -202,11 +202,13 @@ asmlinkage long sys_remap_file_pages(uns
!(vma->vm_flags & VM_NONLINEAR)) {
mapping = vma->vm_file->f_mapping;
spin_lock(&mapping->i_shared_lock);
+ flush_dcache_mmap_lock(mapping);
vma->vm_flags |= VM_NONLINEAR;
vma_prio_tree_remove(vma, &mapping->i_mmap);
vma_prio_tree_init(vma);
list_add_tail(&vma->shared.vm_set.list,
&mapping->i_mmap_nonlinear);
+ flush_dcache_mmap_unlock(mapping);
spin_unlock(&mapping->i_shared_lock);
}
diff -puN mm/mmap.c~rmap-22-flush_dcache_mmap_lock mm/mmap.c
--- 25/mm/mmap.c~rmap-22-flush_dcache_mmap_lock Tue May 4 17:52:28 2004
+++ 25-akpm/mm/mmap.c Tue May 4 17:53:27 2004
@@ -25,6 +25,7 @@
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
+#include <asm/cacheflush.h>
#include <asm/tlb.h>
/*
@@ -74,10 +75,12 @@ static inline void __remove_shared_vm_st
if (vma->vm_flags & VM_SHARED)
mapping->i_mmap_writable--;
+ flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
list_del_init(&vma->shared.vm_set.list);
else
vma_prio_tree_remove(vma, &mapping->i_mmap);
+ flush_dcache_mmap_unlock(mapping);
}
/*
@@ -266,11 +269,13 @@ static inline void __vma_link_file(struc
if (vma->vm_flags & VM_SHARED)
mapping->i_mmap_writable++;
+ flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
list_add_tail(&vma->shared.vm_set.list,
&mapping->i_mmap_nonlinear);
else
vma_prio_tree_insert(vma, &mapping->i_mmap);
+ flush_dcache_mmap_unlock(mapping);
}
}
@@ -350,14 +355,17 @@ void vma_adjust(struct vm_area_struct *v
}
spin_lock(&mm->page_table_lock);
- if (root)
+ if (root) {
+ flush_dcache_mmap_lock(mapping);
vma_prio_tree_remove(vma, root);
+ }
vma->vm_start = start;
vma->vm_end = end;
vma->vm_pgoff = pgoff;
if (root) {
vma_prio_tree_init(vma);
vma_prio_tree_insert(vma, root);
+ flush_dcache_mmap_unlock(mapping);
}
if (next) {
_