path: root/mm
diff options
authorJeremy Fitzhardinge <jeremy@goop.org>2010-12-02 14:31:18 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-12-02 14:51:15 -0800
commit64141da587241301ce8638cc945f8b67853156ec (patch)
treebf11cfe53f606a2bda2342c6286ba637c4848e34 /mm
parent853ff88324a248a9f5da6e110850223db353ec07 (diff)
vmalloc: eagerly clear ptes on vunmap
On stock 2.6.37-rc4, running: # mount lilith:/export /mnt/lilith # find /mnt/lilith/ -type f -print0 | xargs -0 file crashes the machine fairly quickly under Xen. Often it results in oops messages, but the couple of times I tried just now, it just hung quietly and made Xen print some rude messages: (XEN) mm.c:2389:d80 Bad type (saw 7400000000000001 != exp 3000000000000000) for mfn 1d7058 (pfn 18fa7) (XEN) mm.c:964:d80 Attempt to create linear p.t. with write perms (XEN) mm.c:2389:d80 Bad type (saw 7400000000000010 != exp 1000000000000000) for mfn 1d2e04 (pfn 1d1fb) (XEN) mm.c:2965:d80 Error while pinning mfn 1d2e04 Which means the domain tried to map a pagetable page RW, which would allow it to map arbitrary memory, so Xen stopped it. This is because vm_unmap_ram() left some pages mapped in the vmalloc area after NFS had finished with them, and those pages got recycled as pagetable pages while still having these RW aliases. Removing those mappings immediately removes the Xen-visible aliases, and so it has no problem with those pages being reused as pagetable pages. Deferring the TLB flush doesn't upset Xen because it can flush the TLB itself as needed to maintain its invariants. When unmapping a region in the vmalloc space, clear the ptes immediately. There's no point in deferring this because there's no amortization benefit. The TLBs are left dirty, and they are flushed lazily to amortize the cost of the IPIs. This specific motivation for this patch is an oops-causing regression since 2.6.36 when using NFS under Xen, triggered by the NFS client's use of vm_map_ram() introduced in 56e4ebf877b60 ("NFS: readdir with vmapped pages") . XFS also uses vm_map_ram() and could cause similar problems. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Bryan Schumaker <bjschuma@netapp.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Alex Elder <aelder@sgi.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 17 insertions, 11 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a3d66b3dc5c..eb5cc7d00c5 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -31,8 +31,6 @@
#include <asm/tlbflush.h>
#include <asm/shmparam.h>
-bool vmap_lazy_unmap __read_mostly = true;
/*** Page table manipulation functions ***/
static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
@@ -503,9 +501,6 @@ static unsigned long lazy_max_pages(void)
unsigned int log;
- if (!vmap_lazy_unmap)
- return 0;
log = fls(num_online_cpus());
return log * (32UL * 1024 * 1024 / PAGE_SIZE);
@@ -566,7 +561,6 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end,
if (va->va_end > *end)
*end = va->va_end;
nr += (va->va_end - va->va_start) >> PAGE_SHIFT;
- unmap_vmap_area(va);
list_add_tail(&va->purge_list, &valist);
va->flags |= VM_LAZY_FREEING;
va->flags &= ~VM_LAZY_FREE;
@@ -611,10 +605,11 @@ static void purge_vmap_area_lazy(void)
- * Free and unmap a vmap area, caller ensuring flush_cache_vunmap had been
- * called for the correct range previously.
+ * Free a vmap area, caller ensuring that the area has been unmapped
+ * and flush_cache_vunmap had been called for the correct range
+ * previously.
-static void free_unmap_vmap_area_noflush(struct vmap_area *va)
+static void free_vmap_area_noflush(struct vmap_area *va)
va->flags |= VM_LAZY_FREE;
atomic_add((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr);
@@ -623,6 +618,16 @@ static void free_unmap_vmap_area_noflush(struct vmap_area *va)
+ * Free and unmap a vmap area, caller ensuring flush_cache_vunmap had been
+ * called for the correct range previously.
+ */
+static void free_unmap_vmap_area_noflush(struct vmap_area *va)
+ unmap_vmap_area(va);
+ free_vmap_area_noflush(va);
* Free and unmap a vmap area
static void free_unmap_vmap_area(struct vmap_area *va)
@@ -798,7 +803,7 @@ static void free_vmap_block(struct vmap_block *vb)
BUG_ON(tmp != vb);
- free_unmap_vmap_area_noflush(vb->va);
+ free_vmap_area_noflush(vb->va);
call_rcu(&vb->rcu_head, rcu_free_vb);
@@ -936,6 +941,8 @@ static void vb_free(const void *addr, unsigned long size)
+ vunmap_page_range((unsigned long)addr, (unsigned long)addr + size);
BUG_ON(bitmap_allocate_region(vb->dirty_map, offset >> PAGE_SHIFT, order));
@@ -988,7 +995,6 @@ void vm_unmap_aliases(void)
s = vb->va->va_start + (i << PAGE_SHIFT);
e = vb->va->va_start + (j << PAGE_SHIFT);
- vunmap_page_range(s, e);
flush = 1;
if (s < start)