[PATCH 3/3] fs/locks: Use fs-specific l_pid for remote locks

From: Benjamin Coddington
Date: Tue Jun 06 2017 - 13:20:26 EST


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@xxxxxxxxxx>
---
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 104398ccc9b9..6858ec9802d2 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;
}
@@ -2066,9 +2068,18 @@ 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
@@ -2090,7 +2101,7 @@ 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;
@@ -2604,7 +2615,10 @@ 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