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Commit f1d8c162 authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by Linus Torvalds
Browse files

docs: add documentation about /proc/<pid>/fdinfo/<fd> output 



[akpm@linux-foundation.org: tweak documentation]
Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: James Bottomley <jbottomley@parallels.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Helsley <matt.helsley@gmail.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@onelan.co.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent be77196b

Documentation/filesystems/proc.txt

+82 −0
Original line number Original line Diff line number Diff line
@@ -41,6 +41,7 @@ Table of Contents 
  3.5	/proc/<pid>/mountinfo - Information about mounts

  3.5	/proc/<pid>/mountinfo - Information about mounts

  3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm

  3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm

  3.7   /proc/<pid>/task/<tid>/children - Information about task children

  3.7   /proc/<pid>/task/<tid>/children - Information about task children

  3.8   /proc/<pid>/fdinfo/<fd> - Information about opened file





  4	Configuring procfs

  4	Configuring procfs

  4.1	Mount options

  4.1	Mount options
@@ -1633,6 +1634,87 @@ pids, so one need to either stop or freeze processes being inspected 
if precise results are needed.

if precise results are needed.









3.7	/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].



A typical output is



	pos:	0

	flags:	0100002



The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags

pair provide additional information particular to the objects they represent.



	Eventfd files

	~~~~~~~~~~~~~

	pos:	0

	flags:	04002

	eventfd-count:	5a



	where 'eventfd-count' is hex value of a counter.



	Signalfd files

	~~~~~~~~~~~~~~

	pos:	0

	flags:	04002

	sigmask:	0000000000000200



	where 'sigmask' is hex value of the signal mask associated

	with a file.



	Epoll files

	~~~~~~~~~~~

	pos:	0

	flags:	02

	tfd:        5 events:       1d data: ffffffffffffffff



	where 'tfd' is a target file descriptor number in decimal form,

	'events' is events mask being watched and the 'data' is data

	associated with a target [see epoll(7) for more details].



	Fsnotify files

	~~~~~~~~~~~~~~

	For inotify files the format is the following



	pos:	0

	flags:	02000000

	inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d



	where 'wd' is a watch descriptor in decimal form, ie a target file

	descriptor number, 'ino' and 'sdev' are inode and device where the

	target file resides and the 'mask' is the mask of events, all in hex

	form [see inotify(7) for more details].



	If the kernel was built with exportfs support, the path to the target

	file is encoded as a file handle.  The file handle is provided by three

	fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex

	format.



	If the kernel is built without exportfs support the file handle won't be

	printed out.



	For fanotify files the format is



	pos:	0

	flags:	02

	fanotify ino:2 sdev:800013 mask:1 ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:0200000000000000



	or



	pos:	0

	flags:	02

	fanotify mnt_id:13 mask:1 ignored_mask:40000000



	where 'ino', 'sdev' are target inode and device, 'mnt_id' is the mount

	point identifier, 'mask' is the events mask used and 'ignored_mask' is

	the mask of events which are to be ignored. All in hex format.





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Configuring procfs

Configuring procfs

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