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authorMichael S. Tsirkin <mst@redhat.com>2009-09-21 17:03:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:42 -0700
commit3d2d827f5ca5e32816194119d5c980c7e04474a6 (patch)
treefe0e84669f5f20e1dff8e3dc6b191b4d5dfc0145 /mm/mmu_context.c
parent425fbf047cc70bb30dff368a6da02c8c2d229318 (diff)
downloadlinaro-lsk-3d2d827f5ca5e32816194119d5c980c7e04474a6.tar.gz
mm: move use_mm/unuse_mm from aio.c to mm/
Anyone who wants to do copy to/from user from a kernel thread, needs use_mm (like what fs/aio has). Move that into mm/, to make reusing and exporting easier down the line, and make aio use it. Next intended user, besides aio, will be vhost-net. Acked-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmu_context.c')
-rw-r--r--mm/mmu_context.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/mm/mmu_context.c b/mm/mmu_context.c
new file mode 100644
index 00000000000..fd473b51c90
--- /dev/null
+++ b/mm/mmu_context.c
@@ -0,0 +1,55 @@
+/* Copyright (C) 2009 Red Hat, Inc.
+ *
+ * See ../COPYING for licensing terms.
+ */
+
+#include <linux/mm.h>
+#include <linux/mmu_context.h>
+#include <linux/sched.h>
+
+#include <asm/mmu_context.h>
+
+/*
+ * use_mm
+ * Makes the calling kernel thread take on the specified
+ * mm context.
+ * Called by the retry thread execute retries within the
+ * iocb issuer's mm context, so that copy_from/to_user
+ * operations work seamlessly for aio.
+ * (Note: this routine is intended to be called only
+ * from a kernel thread context)
+ */
+void use_mm(struct mm_struct *mm)
+{
+ struct mm_struct *active_mm;
+ struct task_struct *tsk = current;
+
+ task_lock(tsk);
+ active_mm = tsk->active_mm;
+ atomic_inc(&mm->mm_count);
+ tsk->mm = mm;
+ tsk->active_mm = mm;
+ switch_mm(active_mm, mm, tsk);
+ task_unlock(tsk);
+
+ mmdrop(active_mm);
+}
+
+/*
+ * unuse_mm
+ * Reverses the effect of use_mm, i.e. releases the
+ * specified mm context which was earlier taken on
+ * by the calling kernel thread
+ * (Note: this routine is intended to be called only
+ * from a kernel thread context)
+ */
+void unuse_mm(struct mm_struct *mm)
+{
+ struct task_struct *tsk = current;
+
+ task_lock(tsk);
+ tsk->mm = NULL;
+ /* active_mm is still 'mm' */
+ enter_lazy_tlb(mm, tsk);
+ task_unlock(tsk);
+}