Commit 3845f256 authored by Kalesh Singh's avatar Kalesh Singh Committed by Linus Torvalds
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procfs/dmabuf: add inode number to /proc/*/fdinfo 

And 'ino' field to /proc/<pid>/fdinfo/<FD> and
/proc/<pid>/task/<tid>/fdinfo/<FD>.

The inode numbers can be used to uniquely identify DMA buffers in user
space and avoids a dependency on /proc/<pid>/fd/* when accounting
per-process DMA buffer sizes.

Link: https://lkml.kernel.org/r/20210308170651.919148-2-kaleshsingh@google.com


Signed-off-by: default avatarKalesh Singh <kaleshsingh@google.com>
Acked-by: default avatarRandy Dunlap <rdunlap@infradead.org>
Acked-by: default avatarChristian König <christian.koenig@amd.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hridya Valsaraju <hridya@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7bc3fa01

Documentation/filesystems/proc.rst

+31 −6
Original line number Diff line number Diff line
@@ -1920,18 +1920,20 @@ if precise results are needed. 
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 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].

files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'.

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]. 'ino' represents the inode number of

the file.



A typical output is::



	pos:	0

	flags:	0100002

	mnt_id:	19

	ino:	63107



All locks associated with a file descriptor are shown in its fdinfo too::
@@ -1948,6 +1950,7 @@ Eventfd files 
	pos:	0

	flags:	04002

	mnt_id:	9

	ino:	63107

	eventfd-count:	5a



where 'eventfd-count' is hex value of a counter.
@@ -1960,6 +1963,7 @@ Signalfd files 
	pos:	0

	flags:	04002

	mnt_id:	9

	ino:	63107

	sigmask:	0000000000000200



where 'sigmask' is hex value of the signal mask associated
@@ -1973,6 +1977,7 @@ Epoll files 
	pos:	0

	flags:	02

	mnt_id:	9

	ino:	63107

	tfd:        5 events:       1d data: ffffffffffffffff pos:0 ino:61af sdev:7



where 'tfd' is a target file descriptor number in decimal form,
@@ -1989,6 +1994,8 @@ For inotify files the format is the following:: 


	pos:	0

	flags:	02000000

	mnt_id:	9

	ino:	63107

	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, i.e. a target file
@@ -2011,6 +2018,7 @@ For fanotify files the format is:: 
	pos:	0

	flags:	02

	mnt_id:	9

	ino:	63107

	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
@@ -2035,6 +2043,7 @@ Timerfd files 
	pos:	0

	flags:	02

	mnt_id:	9

	ino:	63107

	clockid: 0

	ticks: 0

	settime flags: 01
@@ -2049,6 +2058,22 @@ details]. 'it_value' is remaining time until the timer expiration. 
with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'

still exhibits timer's remaining time.



DMA Buffer files

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



::



	pos:	0

	flags:	04002

	mnt_id:	9

	ino:	63107

	size:   32768

	count:  2

	exp_name:  system-heap



where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of

the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter.



3.9	/proc/<pid>/map_files - Information about memory mapped files

---------------------------------------------------------------------

This directory contains symbolic links which represent memory mapped files

fs/proc/fd.c

+3 −2
Original line number Diff line number Diff line
@@ -54,9 +54,10 @@ static int seq_show(struct seq_file *m, void *v) 
	if (ret)

		return ret;



	seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",

	seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n",

		   (long long)file->f_pos, f_flags,

		   real_mount(file->f_path.mnt)->mnt_id);

		   real_mount(file->f_path.mnt)->mnt_id,

		   file_inode(file)->i_ino);



	/* show_fd_locks() never deferences files so a stale value is safe */

	show_fd_locks(m, file, files);