[RFC][PATCH] ckpt-files: error out on file locks and leases

[Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>]

We do not currently handle the holding of any file locks.
If a process being checkpointed is holding one, error out
of the checkpoint process.

Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
---
 checkpoint/files.c |   12 ++++++++++++
 fs/locks.c         |   35 +++++++++++++++++++++++++++++++++++
 include/linux/fs.h |    6 ++++++
 3 files changed, 53 insertions(+), 0 deletions(-)

diff --git a/checkpoint/files.c b/checkpoint/files.c
index b622588..46a103d 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -272,6 +272,18 @@ static int checkpoint_file_desc(struct ckpt_ctx *ctx,
 	}
 	rcu_read_unlock();
 
+	ret = find_locks_with_owner(file, files);
+	/*
+	 * find_locks_with_owner() returns an error when there
+	 * are no locks found, so we *want* it to return an error
+	 * code.  Its success means we have to fail the checkpoint.
+	 */
+	if (!ret) {
+		ret = -EBADF;
+		ckpt_err(ctx, ret, "%(T)fd %d has file lock or lease\n", fd);
+		goto out;
+	}
+
 	/* sanity check (although this shouldn't happen) */
 	ret = -EBADF;
 	if (!file) {
diff --git a/fs/locks.c b/fs/locks.c
index a8794f2..721481a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1994,6 +1994,41 @@ void locks_remove_posix(struct file *filp, fl_owner_t owner)
 
 EXPORT_SYMBOL(locks_remove_posix);
 
+int find_locks_with_owner(struct file *filp, fl_owner_t owner)
+{
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct file_lock **inode_fl;
+	int ret = -EEXIST;
+
+	lock_kernel();
+	for_each_lock(inode, inode_fl) {
+		struct file_lock *fl = *inode_fl;
+		/*
+		 * We could use posix_same_owner() along with a 'fake'
+		 * file_lock.  But, the fake file will never have the
+		 * same fl_lmops as the fl that we are looking for and
+		 * posix_same_owner() would just fall back to this
+		 * check anyway.
+		 */
+		if (IS_POSIX(fl)) {
+			if (fl->fl_owner == owner) {
+				ret = 0;
+				break;
+			}
+		} else if (IS_FLOCK(fl) || IS_LEASE(fl)) {
+			if (fl->fl_file == filp) {
+				ret = 0;
+				break;
+			}
+		} else {
+			WARN(1, "unknown file lock type, fl_flags: %x",
+				fl->fl_flags);
+		}
+	}
+	unlock_kernel();
+	return ret;
+}
+
 /*
  * This function is called on the last close of an open file.
  */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5ae34fc..089549b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1122,6 +1122,7 @@ extern void locks_remove_posix(struct file *, fl_owner_t);
 extern void locks_remove_flock(struct file *);
 extern void locks_release_private(struct file_lock *);
 extern void posix_test_lock(struct file *, struct file_lock *);
+extern int find_locks_with_owner(struct file *filp, fl_owner_t owner);
 extern int posix_lock_file(struct file *, struct file_lock *, struct file_lock *);
 extern int posix_lock_file_wait(struct file *, struct file_lock *);
 extern int posix_unblock_lock(struct file *, struct file_lock *);
@@ -1190,6 +1191,11 @@ static inline void locks_remove_posix(struct file *filp, fl_owner_t owner)
 	return;
 }
 
+static inline int find_locks_with_owner(struct file *filp, fl_owner_t owner)
+{
+	return -ENOENT;
+}
+
 static inline void locks_remove_flock(struct file *filp)
 {
 	return;
-- 
1.6.6.rc3

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