[RFC][PATCH 4/4][cr]: Restore file_owner info

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

Restore the file-owner information for each 'struct file'.  This is
essentially is like a new fcntl(F_SETOWN) and fcntl(F_SETSIG) calls,
except that the pid, uid, euid and signum values are read from the
checkpoint image.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
 fs/checkpoint.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/fs/checkpoint.c b/fs/checkpoint.c
index 0fa4ce8..73e2bc9 100644
--- a/fs/checkpoint.c
+++ b/fs/checkpoint.c
@@ -615,6 +615,36 @@ static int attach_file(struct file *file)
 	return fd;
 }
 
+static int restore_file_owner(struct ckpt_ctx *ctx, struct ckpt_hdr_file *h,
+		struct file *file)
+{
+	int ret;
+	struct pid *pid;
+
+	ckpt_debug("restore_file_owner(): uid %u, euid %u, pid %d, type %d\n",
+			h->f_owner_uid, h->f_owner_euid, h->f_owner_pid,
+			h->f_owner_pid_type);
+
+	rcu_read_lock();
+	pid = find_vpid(h->f_owner_pid);
+
+	/*
+	 * TODO: Do we need to force==1 or can it be 0 ? 'force' is used to
+	 * 	 modify the owner, if one is already set. Can it be set when
+	 * 	 we restart an application ?
+	 */
+	ret = __f_setown_uid(file, pid, h->f_owner_pid_type, h->f_owner_uid,
+			h->f_owner_euid, 1);
+	rcu_read_unlock();
+
+	file->f_owner.signum = h->f_owner_signum;
+
+	if (ret < 0)
+		ckpt_err(ctx, ret, "__fsetown_uid() failed\n");
+
+	return ret;
+}
+
 #define CKPT_SETFL_MASK  \
 	(O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 
@@ -648,6 +678,10 @@ int restore_file_common(struct ckpt_ctx *ctx, struct file *file,
 	if (ret < 0)
 		return ret;
 
+	ret = restore_file_owner(ctx, h, file);
+	if (ret < 0)
+		return ret;
+
 	/*
 	 * Normally f_mode is set by open, and modified only via
 	 * fcntl(), so its value now should match that at checkpoint.
-- 
1.6.0.4