[PATCH v6 2/2] procfs/dmabuf: Add inode number to /proc/*/fdinfo

From: Kalesh Singh <kaleshsingh@google.com>
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Cc: jannh@google.com, jeffv@google.com, keescook@chromium.org,
	surenb@google.com, minchan@kernel.org, hridya@google.com,
	rdunlap@infradead.org, christian.koenig@amd.com,
	willy@infradead.org, kernel-team@android.com,
	Kalesh Singh <kaleshsingh@google.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	Alexey Gladkov <gladkov.alexey@gmail.com>,
	Anand K Mistry <amistry@google.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Daniel Jordan <daniel.m.jordan@oracle.com>,
	Michel Lespinasse <walken@google.com>,
	Bernd Edlinger <bernd.edlinger@hotmail.de>,
	Andrei Vagin <avagin@gmail.com>,
	Yafang Shao <laoar.shao@gmail.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-doc@vger.kernel.org
Subject: [PATCH v6 2/2] procfs/dmabuf: Add inode number to /proc/*/fdinfo
Date: Mon,  8 Feb 2021 15:53:07 +0000	[thread overview]
Message-ID: <20210208155315.1367371-2-kaleshsingh@google.com> (raw)
In-Reply-To: <20210208155315.1367371-1-kaleshsingh@google.com>

And 'inode_no' 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.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
---
Changes in v5:
  - Fixed tab vs spaces, per Randy
  - Renamed inode_no to ino, per Matthew
Changes in v4:
  - Add inode number as common field in fdinfo, per Christian
Changes in v3:
  - Add documentation in proc.rst, per Randy
Changes in v2:
  - Update patch description

 Documentation/filesystems/proc.rst | 37 +++++++++++++++++++++++++-----
 fs/proc/fd.c                       |  5 ++--
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 2fa69f710e2a..7730d1c120e8 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1902,18 +1902,20 @@ 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::
 
@@ -1930,6 +1932,7 @@ Eventfd files
 	pos:	0
 	flags:	04002
 	mnt_id:	9
+	ino:	63107
 	eventfd-count:	5a
 
 where 'eventfd-count' is hex value of a counter.
@@ -1942,6 +1945,7 @@ Signalfd files
 	pos:	0
 	flags:	04002
 	mnt_id:	9
+	ino:	63107
 	sigmask:	0000000000000200
 
 where 'sigmask' is hex value of the signal mask associated
@@ -1955,6 +1959,7 @@ 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,
@@ -1971,6 +1976,8 @@ 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
@@ -1993,6 +2000,7 @@ 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
@@ -2017,6 +2025,7 @@ Timerfd files
 	pos:	0
 	flags:	02
 	mnt_id:	9
+	ino:	63107
 	clockid: 0
 	ticks: 0
 	settime flags: 01
@@ -2031,6 +2040,22 @@ 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
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 585e213301f9..822efd20b922 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -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);
-- 
2.30.0.478.g8a0d178c01-goog

