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authorAndrey Vagin <avagin@openvz.org>2014-04-07 15:38:34 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-07 16:36:04 -0700
commit49d063cb353265c3af701bab215ac438ca7df36d (patch)
treed69fa40233df60a711965a37c8bd68c1f86edd1f /Documentation
parentf0b5664ba770190fa528ba72f8f6294cca797103 (diff)
downloadlinux-49d063cb353265c3af701bab215ac438ca7df36d.tar.gz
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 <avagin@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com> Acked-by: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Rob Landley <rob@landley.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/proc.txt17
1 files changed, 12 insertions, 5 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index f00bee144ad..8b9cd8eb3f9 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/<pid>/fdinfo/<fd> - Information about opened file
+3.8 /proc/<pid>/fdinfo/<fd> - 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/<pid>/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