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linux/fs/proc
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Andrey Vagin 6c8c90319c 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>
2015-04-17 09:04:12 -04:00
..
array.c proc: remove use of seq_printf return value 2015-04-15 16:35:25 -07:00
base.c proc: remove use of seq_printf return value 2015-04-15 16:35:25 -07:00
cmdline.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
consoles.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
cpuinfo.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
devices.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
fd.c proc: show locks in /proc/pid/fdinfo/X 2015-04-17 09:04:12 -04:00
fd.h
generic.c procfs: fix race between symlink removals and traversals 2015-02-22 11:43:12 -05:00
inode.c procfs: fix race between symlink removals and traversals 2015-02-22 11:43:12 -05:00
internal.h procfs: fix race between symlink removals and traversals 2015-02-22 11:43:12 -05:00
interrupts.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Kconfig
kcore.c fs/proc/kcore.c: don't add modules range to kcore if it's equal to vmcore range 2014-10-09 22:25:50 -04:00
kmsg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
loadavg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Makefile proc: Implement /proc/thread-self to point at the directory of the current thread 2014-08-04 10:07:11 -07:00
meminfo.c fs/proc/meminfo.c: include cma info in proc/meminfo 2014-12-18 19:08:10 -08:00
namespaces.c kill proc_ns completely 2014-12-10 21:30:57 -05:00
nommu.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
page.c mm:add KPF_ZERO_PAGE flag for /proc/kpageflags 2015-02-11 17:06:00 -08:00
proc_net.c fs/proc: use a rb tree for the directory entries 2014-12-10 17:41:09 -08:00
proc_sysctl.c sysctl: remove typedef ctl_table 2014-08-08 15:57:24 -07:00
proc_tty.c proc: remove proc_tty_ldisc variable 2014-08-08 15:57:22 -07:00
root.c fs/proc: use a rb tree for the directory entries 2014-12-10 17:41:09 -08:00
self.c new helper: readlink_copy() 2014-04-01 23:19:15 -04:00
softirqs.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
stat.c genirq: Prevent proc race against freeing of irq descriptors 2014-12-13 13:33:07 +01:00
task_mmu.c pagemap: do not leak physical addresses to non-privileged userspace 2015-03-17 09:31:30 -07:00
task_nommu.c proc/maps: make vm_is_stack() logic namespace-friendly 2014-10-09 22:25:50 -04:00
thread_self.c proc: Implement /proc/thread-self to point at the directory of the current thread 2014-08-04 10:07:11 -07:00
uptime.c cputime: Default implementation of nsecs -> cputime conversion 2014-03-13 15:56:43 +01:00
version.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
vmcore.c vmcore: fix PT_NOTE n_namesz, n_descsz overflow issue 2015-02-17 14:34:52 -08:00