proc: show locks in /proc/pid/fdinfo/X
Let's show locks which are associated with a file descriptor in
its fdinfo file.
Currently we don't have a reliable way to determine who holds a lock. We
can find some information in /proc/locks, but PID which is reported there
can be wrong. For example, a process takes a lock, then forks a child and
dies. In this case /proc/locks contains the parent pid, which can be
reused by another process.
$ cat /proc/locks
...
6: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF
...
$ ps -C rpcbind
PID TTY TIME CMD
332 ? 00:00:00 rpcbind
$ cat /proc/332/fdinfo/4
pos: 0
flags: 0100000
mnt_id: 22
lock: 1: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF
$ ls -l /proc/332/fd/4
lr-x------ 1 root root 64 Mar 5 14:43 /proc/332/fd/4 -> /run/rpcbind.lock
$ ls -l /proc/324/fd/
total 0
lrwx------ 1 root root 64 Feb 27 14:50 0 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:50 1 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:49 2 -> /dev/pts/0
You can see that the process with the 324 pid doesn't hold the lock.
This information is required for proper dumping and restoring file
locks.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 8e5ad83..af84ad0 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -8,6 +8,7 @@
#include <linux/security.h>
#include <linux/file.h>
#include <linux/seq_file.h>
+#include <linux/fs.h>
#include <linux/proc_fs.h>
@@ -48,17 +49,23 @@
put_files_struct(files);
}
- if (!ret) {
- seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
- (long long)file->f_pos, f_flags,
- real_mount(file->f_path.mnt)->mnt_id);
- if (file->f_op->show_fdinfo)
- file->f_op->show_fdinfo(m, file);
- ret = seq_has_overflowed(m);
- fput(file);
- }
+ if (ret)
+ return ret;
- return ret;
+ seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
+ (long long)file->f_pos, f_flags,
+ real_mount(file->f_path.mnt)->mnt_id);
+
+ show_fd_locks(m, file, files);
+ if (seq_has_overflowed(m))
+ goto out;
+
+ if (file->f_op->show_fdinfo)
+ file->f_op->show_fdinfo(m, file);
+
+out:
+ fput(file);
+ return 0;
}
static int seq_fdinfo_open(struct inode *inode, struct file *file)