Messages in this thread Patch in this message | | | Date | Tue, 4 Nov 2008 15:38:05 -0600 | From | "Serge E. Hallyn" <> | Subject | Re: [RFC v8][PATCH 0/12] Kernel based checkpoint/restart |
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Quoting Oren Laadan (orenl@cs.columbia.edu): > Basic checkpoint-restart [C/R]: v8 adds support for "external" checkpoint > and improves documentation. Older announcements below.
Finally!
From 8edab186b605f7dddd612e581204f1ad8fd766be Mon Sep 17 00:00:00 2001 From: Serge Hallyn <serue@us.ibm.com> Date: Tue, 4 Nov 2008 15:28:01 -0600 Subject: [PATCH 1/1] cr: fix use of __d_path()
__d_path(): 1. should be used under dcache_lock 2. can change root->{mnt,dentry} without changing refcounts The second point was the cause of my BUGs. The ctx->root was passed in, and do_checkpoint() had taken a path_get on the vfsroot. So now at cleanup it was doing path_put() using another mnt+dentry.
(Why they are different, I'm not sure - but my guess would be that stdin or stdout is inherited from the parent task in parent mntns, hence file->mnt is different from root->mnt as it's a different namespace.)
Signed-off-by: Serge Hallyn <serue@us.ibm.com> --- checkpoint/checkpoint.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-)
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c index 173b637..7f0c1e7 100644 --- a/checkpoint/checkpoint.c +++ b/checkpoint/checkpoint.c @@ -70,9 +70,20 @@ static char * cr_fill_fname(struct path *path, struct path *root, char *buf, int *n) { char *fname; + struct path root2; + + root2.mnt = root->mnt; + root2.dentry = root->dentry; BUG_ON(!buf); - fname = __d_path(path, root, buf, *n); + spin_lock(&dcache_lock); + fname = __d_path(path, &root2, buf, *n); + spin_unlock(&dcache_lock); + if (root2.mnt != root->mnt) + printk(KERN_NOTICE "%s: mnt changed\n", __func__); + if (root2.dentry != root->dentry) + printk(KERN_NOTICE "%s: dentry changed\n", __func__); + fname = buf+10; if (!IS_ERR(fname)) *n = (buf + (*n) - fname); return fname; -- 1.5.6.3
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