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    SubjectRe: [PATCH 3/3] fs/locks: Use fs-specific l_pid for remote locks
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    On Tue, 2017-06-06 at 16:45 -0400, Benjamin Coddington wrote:
    > 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.
    >

    Actually, you're not translating anything for F_GETLK until we get to
    this patch. Patch #2 in this series removes the fl_nspid field, but the
    pid translation isn't fixed until here. That does mean a nominal
    regression here in how fl_pid is reported between the two.

    Would it be best to squash #2 and #3 together? Or maybe just go ahead
    and universally translate the fl_pid field until you add the flag in
    this patch?

    Also to make sure I understand: task->tgid will always represent the
    task's pid in the init_pid_ns, right?

    Other than the minor bisectability concern, I think this looks good.
    Nice work!

    > Signed-off-by: Benjamin Coddington <bcodding@redhat.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)
    >

    --
    Jeff Layton <jlayton@poochiereds.net>

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