From 49d063cb353265c3af701bab215ac438ca7df36d Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Mon, 7 Apr 2014 15:38:34 -0700 Subject: [PATCH] proc: show mnt_id in /proc/pid/fdinfo Currently we don't have a way how to determing from which mount point file has been opened. This information is required for proper dumping and restoring file descriptos due to presence of mount namespaces. It's possible, that two file descriptors are opened using the same paths, but one fd references mount point from one namespace while the other fd -- from other namespace. $ ls -l /proc/1/fd/1 lrwx------ 1 root root 64 Mar 19 23:54 /proc/1/fd/1 -> /dev/null $ cat /proc/1/fdinfo/1 pos: 0 flags: 0100002 mnt_id: 16 $ cat /proc/1/mountinfo | grep ^16 16 32 0:4 / /dev rw,nosuid shared:2 - devtmpfs devtmpfs rw,size=1013356k,nr_inodes=253339,mode=755 Signed-off-by: Andrey Vagin Acked-by: Pavel Emelyanov Acked-by: Cyrill Gorcunov Cc: Rob Landley Cc: Al Viro Cc: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/filesystems/proc.txt | 17 ++++++++++++----- fs/proc/fd.c | 6 ++++-- 2 files changed, 16 insertions(+), 7 deletions(-) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index f00bee14..8b9cd8e 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1648,18 +1648,21 @@ pids, so one need to either stop or freeze processes being inspected if precise results are needed. -3.7 /proc//fdinfo/ - Information about opened file +3.8 /proc//fdinfo/ - Information about opened file --------------------------------------------------------------- This file provides information associated with an opened file. The regular -files have at least two fields -- 'pos' and 'flags'. The 'pos' represents -the current offset of the opened file in decimal form [see lseek(2) for -details] and 'flags' denotes the octal O_xxx mask the file has been -created with [see open(2) for details]. +files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos' +represents the current offset of the opened file in decimal form [see lseek(2) +for details], 'flags' denotes the octal O_xxx mask the file has been +created with [see open(2) for details] and 'mnt_id' represents mount ID of +the file system containing the opened file [see 3.5 /proc//mountinfo +for details]. A typical output is pos: 0 flags: 0100002 + mnt_id: 19 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags pair provide additional information particular to the objects they represent. @@ -1668,6 +1671,7 @@ pair provide additional information particular to the objects they represent. ~~~~~~~~~~~~~ pos: 0 flags: 04002 + mnt_id: 9 eventfd-count: 5a where 'eventfd-count' is hex value of a counter. @@ -1676,6 +1680,7 @@ pair provide additional information particular to the objects they represent. ~~~~~~~~~~~~~~ pos: 0 flags: 04002 + mnt_id: 9 sigmask: 0000000000000200 where 'sigmask' is hex value of the signal mask associated @@ -1685,6 +1690,7 @@ pair provide additional information particular to the objects they represent. ~~~~~~~~~~~ pos: 0 flags: 02 + mnt_id: 9 tfd: 5 events: 1d data: ffffffffffffffff where 'tfd' is a target file descriptor number in decimal form, @@ -1718,6 +1724,7 @@ pair provide additional information particular to the objects they represent. pos: 0 flags: 02 + mnt_id: 9 fanotify flags:10 event-flags:0 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 985ea88..0788d09 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -11,6 +11,7 @@ #include +#include "../mount.h" #include "internal.h" #include "fd.h" @@ -48,8 +49,9 @@ static int seq_show(struct seq_file *m, void *v) } if (!ret) { - seq_printf(m, "pos:\t%lli\nflags:\t0%o\n", - (long long)file->f_pos, f_flags); + 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) ret = file->f_op->show_fdinfo(m, file); fput(file); -- 2.7.4