The task address space (task->mm) may be shared between processes if
CLONE_VM is used, and particularly among threads. Accordingly, treat
'task->mm' as a shared object: during checkpoint check against the
objhash and only dump the contents if seen for the first time. During
restart, likewise, only restore if it's a new instance, otherwise use
the one already registered in the objhash.
Signed-off-by: Oren Laadan <or...@cs.columbia.edu>
---
checkpoint/ckpt_mem.c | 36 +++++++++++++++++++++++-------------
checkpoint/objhash.c | 6 ++++++
checkpoint/rstr_mem.c | 31 +++++++++++++++++++++++++++----
include/linux/checkpoint.h | 1 +
4 files changed, 57 insertions(+), 17 deletions(-)
diff --git a/checkpoint/ckpt_mem.c b/checkpoint/ckpt_mem.c
index 92a3edc..0df3cda 100644
--- a/checkpoint/ckpt_mem.c
+++ b/checkpoint/ckpt_mem.c
@@ -733,22 +733,29 @@ int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t)
struct cr_hdr_mm *hh;
struct mm_struct *mm;
struct vm_area_struct *vma;
- int objref, ret;
+ int objref, new;
+ int ret;
+
+ mm = get_task_mm(t);
+
+ new = cr_obj_add_ptr(ctx, mm, &objref, CR_OBJ_MM, 0);
+ if (new < 0) {
+ ret = new;
+ goto mmput;
+ }
h.type = CR_HDR_MM;
h.len = sizeof(*hh);
+ ret = -ENOMEM;
hh = cr_hbuf_get(ctx, sizeof(*hh));
if (!hh)
- return -ENOMEM;
+ goto mmput;
- mm = get_task_mm(t);
+ down_read(&mm->mmap_sem);
- objref = 0; /* will be meaningful with multiple processes */
hh->objref = objref;
- down_read(&mm->mmap_sem);
-
hh->start_code = mm->start_code;
hh->end_code = mm->end_code;
hh->start_data = mm->start_data;
@@ -770,17 +777,20 @@ int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t)
if (ret < 0)
goto out;
- /* write the vma's */
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
- ret = cr_write_vma(ctx, vma);
- if (ret < 0)
- goto out;
- }
+ if (new) {
+ /* write the vma's */
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ ret = cr_write_vma(ctx, vma);
+ if (ret < 0)
+ goto out;
+ }
- ret = cr_write_mm_context(ctx, mm);
+ ret = cr_write_mm_context(ctx, mm);
+ }
out:
up_read(&mm->mmap_sem);
+ mmput:
mmput(mm);
return ret;
}
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index 25916c1..6584579 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -38,6 +38,9 @@ static void cr_obj_ref_drop(struct cr_objref *obj)
case CR_OBJ_INODE:
iput((struct inode *) obj->ptr);
break;
+ case CR_OBJ_MM:
+ mmput((struct mm_struct *) obj->ptr);
+ break;
default:
BUG();
}
@@ -55,6 +58,9 @@ static int cr_obj_ref_grab(struct cr_objref *obj)
if (!igrab((struct inode *) obj->ptr))
ret = -EBADF;
break;
+ case CR_OBJ_MM:
+ atomic_inc(&((struct mm_struct *) obj->ptr)->mm_users);
+ break;
default:
BUG();
}
diff --git a/checkpoint/rstr_mem.c b/checkpoint/rstr_mem.c
index da3eb0e..7e73129 100644
--- a/checkpoint/rstr_mem.c
+++ b/checkpoint/rstr_mem.c
@@ -505,16 +505,39 @@ int cr_read_mm(struct cr_ctx *ctx)
if (ret < 0)
goto out;
- cr_debug("map_count %d\n", hh->map_count);
+ cr_debug("map_count %d objref %d\n", hh->map_count, hh->objref);
- /* XXX need more sanity checks */
+ /* FIX need more sanity checks */
ret = -EINVAL;
- if ((hh->start_code > hh->end_code) ||
- (hh->start_data > hh->end_data))
+ if (hh->objref < 0)
goto out;
+ if ((hh->start_code > hh->end_code) || (hh->start_data > hh->end_data))
+ goto out;
+
+ /* if the mm's objref is in the objhash, use that instance */
+ mm = cr_obj_get_by_ref(ctx, hh->objref, CR_OBJ_MM);
+ if (IS_ERR(mm)) {
+ ret = PTR_ERR(mm);
+ goto out;
+ }
+ if (mm) {
+ if (mm != current->mm) {
+ ret = exec_mmap(mm);
+ if (ret < 0)
+ goto out;
+ atomic_inc(&mm->mm_users);
+ }
+ ret = 0;
+ goto out;
+ }
+
+ /* otherwise, add our mm to the objhash for future generations */
mm = current->mm;
+ ret = cr_obj_add_ref(ctx, mm, hh->objref, CR_OBJ_MM, 0);
+ if (ret < 0)
+ goto out;
/* point of no return -- destruct current mm */
down_write(&mm->mmap_sem);
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 043535c..1bfe284 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -77,6 +77,7 @@ extern void cr_ctx_put(struct cr_ctx *ctx);
enum {
CR_OBJ_FILE = 1,
CR_OBJ_INODE,
+ CR_OBJ_MM,
CR_OBJ_MAX
};
--
1.5.4.3
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