linux-kernel - [PATCH 3/3] fs/locks: Use fs-specific l

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Date:   Tue,  6 Jun 2017 16:45:23 -0400
From:   Benjamin Coddington <bcodding@...hat.com>
To:     Jeff Layton <jlayton@...chiereds.net>, bfields@...ldses.org,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] fs/locks: Use fs-specific l_pid for remote locks

Now that we're translating fl_pid for F_GETLK and /proc/locks, we need to
handle the case where a remote filesystem directly sets fl_pid.  In that
case, the fl_pid should not be translated into a local pid namespace.  If
the filesystem implements the lock operation, set a flag to return the
lock's fl_pid value directly, rather translate it.

Signed-off-by: Benjamin Coddington <bcodding@...hat.com>
---
 fs/locks.c         | 22 ++++++++++++++++++----
 include/linux/fs.h |  1 +
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 8d48e4c42ed3..206a46d28bbd 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2034,8 +2034,10 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
  */
 int vfs_test_lock(struct file *filp, struct file_lock *fl)
 {
-	if (filp->f_op->lock && is_remote_lock(filp))
+	if (filp->f_op->lock && is_remote_lock(filp)) {
+		fl->fl_flags |= FL_PID_PRIV;
 		return filp->f_op->lock(filp, F_GETLK, fl);
+	}
 	posix_test_lock(filp, fl);
 	return 0;
 }
@@ -2060,9 +2062,18 @@ static pid_t locks_translate_pid(int init_nr, struct pid_namespace *ns)
 	return vnr;
 }
 
+static pid_t flock_translate_pid(struct file_lock *fl)
+{
+	if (IS_OFDLCK(fl))
+		return -1;
+	if (fl->fl_flags & FL_PID_PRIV)
+		return fl->fl_pid;
+	return locks_translate_pid(fl->fl_pid,  task_active_pid_ns(current));
+}
+
 static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
 {
-	flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
+	flock->l_pid = flock_translate_pid(fl);
 #if BITS_PER_LONG == 32
 	/*
 	 * Make sure we can represent the posix lock via
@@ -2084,7 +2095,7 @@ static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
 #if BITS_PER_LONG == 32
 static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
 {
-	flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
+	flock->l_pid = flock_translate_pid(fl);
 	flock->l_start = fl->fl_start;
 	flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
 		fl->fl_end - fl->fl_start + 1;
@@ -2598,7 +2609,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	unsigned int fl_pid;
 	struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
 
-	fl_pid = locks_translate_pid(fl->fl_pid, proc_pidns);
+	if (fl->fl_flags & FL_PID_PRIV)
+		fl_pid = fl->fl_pid;
+	else
+		fl_pid = locks_translate_pid(fl->fl_pid, proc_pidns);
 	/*
 	 * If there isn't a fl_pid don't display who is waiting on
 	 * the lock if we are called from locks_show, or if we are
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b013fac515f7..179496a9719d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -908,6 +908,7 @@ static inline struct file *get_file(struct file *f)
 #define FL_UNLOCK_PENDING	512 /* Lease is being broken */
 #define FL_OFDLCK	1024	/* lock is "owned" by struct file */
 #define FL_LAYOUT	2048	/* outstanding pNFS layout */
+#define FL_PID_PRIV	4096	/* F_GETLK should report fl_pid */
 
 #define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)
 
-- 
2.9.3