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