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authorAndrea Arcangeli <andrea@qumranet.com>2008-07-28 15:46:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-28 16:30:21 -0700
commit7906d00cd1f687268f0a3599442d113767795ae6 (patch)
tree63609454d164a088d7f535f826764579c0f297f6 /include
parent6beeac76f5f96590fb751af5e138fbc3f62e8460 (diff)
mmu-notifiers: add mm_take_all_locks() operation
mm_take_all_locks holds off reclaim from an entire mm_struct. This allows mmu notifiers to register into the mm at any time with the guarantee that no mmu operation is in progress on the mm. This operation locks against the VM for all pte/vma/mm related operations that could ever happen on a certain mm. This includes vmtruncate, try_to_unmap, and all page faults. The caller must take the mmap_sem in write mode before calling mm_take_all_locks(). The caller isn't allowed to release the mmap_sem until mm_drop_all_locks() returns. mmap_sem in write mode is required in order to block all operations that could modify pagetables and free pages without need of altering the vma layout (for example populate_range() with nonlinear vmas). It's also needed in write mode to avoid new anon_vmas to be associated with existing vmas. A single task can't take more than one mm_take_all_locks() in a row or it would deadlock. mm_take_all_locks() and mm_drop_all_locks are expensive operations that may have to take thousand of locks. mm_take_all_locks() can fail if it's interrupted by signals. When mmu_notifier_register returns, we must be sure that the driver is notified if some task is in the middle of a vmtruncate for the 'mm' where the mmu notifier was registered (mmu_notifier_invalidate_range_start/end is run around the vmtruncation but mmu_notifier_register can run after mmu_notifier_invalidate_range_start and before mmu_notifier_invalidate_range_end). Same problem for rmap paths. And we've to remove page pinning to avoid replicating the tlb_gather logic inside KVM (and GRU doesn't work well with page pinning regardless of needing tlb_gather), so without mm_take_all_locks when vmtruncate frees the page, kvm would have no way to notice that it mapped into sptes a page that is going into the freelist without a chance of any further mmu_notifier notification. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Andrea Arcangeli <andrea@qumranet.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Jack Steiner <steiner@sgi.com> Cc: Robin Holt <holt@sgi.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Kanoj Sarcar <kanojsarcar@yahoo.com> Cc: Roland Dreier <rdreier@cisco.com> Cc: Steve Wise <swise@opengridcomputing.com> Cc: Avi Kivity <avi@qumranet.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Anthony Liguori <aliguori@us.ibm.com> Cc: Chris Wright <chrisw@redhat.com> Cc: Marcelo Tosatti <marcelo@kvack.org> Cc: Eric Dumazet <dada1@cosmosbay.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Izik Eidus <izike@qumranet.com> Cc: Anthony Liguori <aliguori@us.ibm.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mm.h3
-rw-r--r--include/linux/pagemap.h1
-rw-r--r--include/linux/rmap.h8
3 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6e695eaab4ce..866a3dbe5c75 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1104,6 +1104,9 @@ extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
unsigned long addr, unsigned long len, pgoff_t pgoff);
extern void exit_mmap(struct mm_struct *);
+extern int mm_take_all_locks(struct mm_struct *mm);
+extern void mm_drop_all_locks(struct mm_struct *mm);
+
#ifdef CONFIG_PROC_FS
/* From fs/proc/base.c. callers must _not_ hold the mm's exe_file_lock */
extern void added_exe_file_vma(struct mm_struct *mm);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a81d81890422..a39b38ccdc97 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -20,6 +20,7 @@
*/
#define AS_EIO (__GFP_BITS_SHIFT + 0) /* IO error on async write */
#define AS_ENOSPC (__GFP_BITS_SHIFT + 1) /* ENOSPC on async write */
+#define AS_MM_ALL_LOCKS (__GFP_BITS_SHIFT + 2) /* under mm_take_all_locks() */
static inline void mapping_set_error(struct address_space *mapping, int error)
{
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 1383692ac5bd..69407f85e10b 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -26,6 +26,14 @@
*/
struct anon_vma {
spinlock_t lock; /* Serialize access to vma list */
+ /*
+ * NOTE: the LSB of the head.next is set by
+ * mm_take_all_locks() _after_ taking the above lock. So the
+ * head must only be read/written after taking the above lock
+ * to be sure to see a valid next pointer. The LSB bit itself
+ * is serialized by a system wide lock only visible to
+ * mm_take_all_locks() (mm_all_locks_mutex).
+ */
struct list_head head; /* List of private "related" vmas */
};