[PATCH -mm 5/10] unshare system call: allow unsharing of vm
If vm structure is being shared, allocate a new one and
copy information from the current, shared, structure.
Changes since -v4 of this patch submitted on 12/13/05:
- none
Signed-off-by: Janak Desai <[email protected]>
---
fork.c | 87 +++++++++++++++++++++++++++++++++++++++++------------------------
1 files changed, 56 insertions(+), 31 deletions(-)
diff -Naurp 2.6.15-mm3+unsh-ns/kernel/fork.c 2.6.15-mm3+unsh-vm/kernel/fork.c
--- 2.6.15-mm3+unsh-ns/kernel/fork.c 2006-01-12 00:39:49.000000000 +0000
+++ 2.6.15-mm3+unsh-vm/kernel/fork.c 2006-01-12 00:47:33.000000000 +0000
@@ -446,6 +446,55 @@ void mm_release(struct task_struct *tsk,
}
}
+/*
+ * Allocate a new mm structure and copy contents from the
+ * mm structure of the passed in task structure.
+ */
+static struct mm_struct *dup_mm(struct task_struct *tsk)
+{
+ struct mm_struct *mm, *oldmm = current->mm;
+ int err;
+
+ if (!oldmm)
+ return NULL;
+
+ mm = allocate_mm();
+ if (!mm)
+ goto fail_nomem;
+
+ memcpy(mm, oldmm, sizeof(*mm));
+
+ if (!mm_init(mm))
+ goto fail_nomem;
+
+ if (init_new_context(tsk, mm))
+ goto fail_nocontext;
+
+ err = dup_mmap(mm, oldmm);
+ if (err)
+ goto free_pt;
+
+ mm->hiwater_rss = get_mm_rss(mm);
+ mm->hiwater_vm = mm->total_vm;
+
+ return mm;
+
+free_pt:
+ mmput(mm);
+
+fail_nomem:
+ return NULL;
+
+fail_nocontext:
+ /*
+ * If init_new_context() failed, we cannot use mmput() to free the mm
+ * because it calls destroy_context()
+ */
+ mm_free_pgd(mm);
+ free_mm(mm);
+ return NULL;
+}
+
static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
{
struct mm_struct * mm, *oldmm;
@@ -473,43 +522,17 @@ static int copy_mm(unsigned long clone_f
}
retval = -ENOMEM;
- mm = allocate_mm();
+ mm = dup_mm(tsk);
if (!mm)
goto fail_nomem;
- /* Copy the current MM stuff.. */
- memcpy(mm, oldmm, sizeof(*mm));
- if (!mm_init(mm))
- goto fail_nomem;
-
- if (init_new_context(tsk,mm))
- goto fail_nocontext;
-
- retval = dup_mmap(mm, oldmm);
- if (retval)
- goto free_pt;
-
- mm->hiwater_rss = get_mm_rss(mm);
- mm->hiwater_vm = mm->total_vm;
-
good_mm:
tsk->mm = mm;
tsk->active_mm = mm;
return 0;
-free_pt:
- mmput(mm);
fail_nomem:
return retval;
-
-fail_nocontext:
- /*
- * If init_new_context() failed, we cannot use mmput() to free the mm
- * because it calls destroy_context()
- */
- mm_free_pgd(mm);
- free_mm(mm);
- return retval;
}
static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
@@ -1423,18 +1446,20 @@ static int unshare_sighand(unsigned long
}
/*
- * Unsharing of vm for tasks created with CLONE_VM is not supported yet
+ * Unshare vm if it is being shared
*/
static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
{
struct mm_struct *mm = current->mm;
if ((unshare_flags & CLONE_VM) &&
- (mm && atomic_read(&mm->mm_users) > 1))
- return -EINVAL;
+ (mm && atomic_read(&mm->mm_users) > 1)) {
+ *new_mmp = dup_mm(current);
+ if (!*new_mmp)
+ return -ENOMEM;
+ }
return 0;
-
}
/*
-
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