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Subject[PATCH 2/2] fs/locks: Remove fl_nspid and use fs-specific l_pid for remote locks
Date
Since commit c69899a17ca4 "NFSv4: Update of VFS byte range lock must be
atomic with the stateid update", NFSv4 has been inserting locks in rpciod
worker context. The result is that the file_lock's fl_nspid is the
kworker's pid instead of the original userspace pid.

The fl_nspid is only used to represent the namespaced virtual pid number
when displaying locks or returning from F_GETLK. There's no reason to set
it for every inserted lock, since we can usually just look it up from
fl_pid. So, instead of looking up and holding struct pid for every lock,
let's just look up the virtual pid number from fl_pid when it is needed.
That means we can remove fl_nspid entirely.

Also, if we're now 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@redhat.com>
---
fs/locks.c | 70 +++++++++++++++++++++++++++++++++++-------------------
include/linux/fs.h | 2 +-
2 files changed, 46 insertions(+), 26 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index d7daa6c8932f..206a46d28bbd 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -733,7 +733,6 @@ static void locks_wake_up_blocks(struct file_lock *blocker)
static void
locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before)
{
- fl->fl_nspid = get_pid(task_tgid(current));
list_add_tail(&fl->fl_list, before);
locks_insert_global_locks(fl);
}
@@ -743,10 +742,6 @@ locks_unlink_lock_ctx(struct file_lock *fl)
{
locks_delete_global_locks(fl);
list_del_init(&fl->fl_list);
- if (fl->fl_nspid) {
- put_pid(fl->fl_nspid);
- fl->fl_nspid = NULL;
- }
locks_wake_up_blocks(fl);
}

@@ -823,8 +818,6 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
if (posix_locks_conflict(fl, cfl)) {
locks_copy_conflock(fl, cfl);
- if (cfl->fl_nspid)
- fl->fl_pid = pid_vnr(cfl->fl_nspid);
goto out;
}
}
@@ -2041,16 +2034,46 @@ 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;
}
EXPORT_SYMBOL_GPL(vfs_test_lock);

+/**
+ * locks_translate_pid - translate a pid number into a namespace
+ * @nr: The pid number in the init_pid_ns
+ * @ns: The namespace into which the pid should be translated
+ *
+ * Used to tranlate a fl_pid into a namespace virtual pid number
+ */
+static pid_t locks_translate_pid(int init_nr, struct pid_namespace *ns)
+{
+ pid_t vnr;
+ struct pid *pid;
+
+ rcu_read_lock();
+ pid = find_pid_ns(init_nr, &init_pid_ns);
+ vnr = pid_nr_ns(pid, ns);
+ rcu_read_unlock();
+ 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
@@ -2072,7 +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;
@@ -2584,22 +2607,19 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
{
struct inode *inode = NULL;
unsigned int fl_pid;
+ struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;

- if (fl->fl_nspid) {
- struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
-
- /* Don't let fl_pid change based on who is reading the file */
- fl_pid = pid_nr_ns(fl->fl_nspid, 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
- * called from __show_fd_info - skip lock entirely
- */
- if (fl_pid == 0)
- return;
- } else
+ 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
+ * called from __show_fd_info - skip lock entirely
+ */
+ if (fl_pid == 0)
+ return;

if (fl->fl_file != NULL)
inode = locks_inode(fl->fl_file);
@@ -2674,7 +2694,7 @@ static int locks_show(struct seq_file *f, void *v)

fl = hlist_entry(v, struct file_lock, fl_link);

- if (fl->fl_nspid && !pid_nr_ns(fl->fl_nspid, proc_pidns))
+ if (locks_translate_pid(fl->fl_pid, proc_pidns) == 0)
return 0;

lock_get_status(f, fl, iter->li_pos, "");
diff --git a/include/linux/fs.h b/include/linux/fs.h
index aa4affb38c39..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)

@@ -984,7 +985,6 @@ struct file_lock {
unsigned char fl_type;
unsigned int fl_pid;
int fl_link_cpu; /* what cpu's list is this on? */
- struct pid *fl_nspid;
wait_queue_head_t fl_wait;
struct file *fl_file;
loff_t fl_start;
--
2.9.3
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