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Message-ID: <753e0a3b-ce7c-5518-65b1-f743dd370b76@infradead.org>
Date: Fri, 5 Feb 2021 16:39:51 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Kalesh Singh <kaleshsingh@...gle.com>
Cc: jannh@...gle.com, jeffv@...gle.com, keescook@...omium.org,
surenb@...gle.com, minchan@...nel.org, hridya@...gle.com,
christian.koenig@....com, kernel-team@...roid.com,
Alexey Dobriyan <adobriyan@...il.com>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
Michal Hocko <mhocko@...e.com>,
Alexey Gladkov <gladkov.alexey@...il.com>,
NeilBrown <neilb@...e.de>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Michel Lespinasse <walken@...gle.com>,
Bernd Edlinger <bernd.edlinger@...mail.de>,
Andrei Vagin <avagin@...il.com>,
Yafang Shao <laoar.shao@...il.com>,
Christian Brauner <christian.brauner@...ntu.com>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-doc@...r.kernel.org
Subject: Re: [PATCH v4 2/2] dmabuf: Add dmabuf inode number to /proc/*/fdinfo
On 2/5/21 1:33 PM, Kalesh Singh wrote:
> 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@...gle.com>
> ---
> 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..db46da32230c 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 'inode_no'.
> +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]. 'inode_no' represents the inode number
> +of the file.
>
> A typical output is::
>
> pos: 0
> flags: 0100002
> mnt_id: 19
> + inode_no: 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
> + inode_no: 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
> + inode_no: 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
> + inode_no: 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
> + inode_no: 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
> + inode_no: 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
> + inode_no: 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
> + inode_no: 63107
Hi,
Why do all of the examples have so many spaces between inode_no:
and the number?
Ah, it's a \t in the output along with the length of the "inode_no:"
string. OK.
Next question: why are there spaces instead of a tab between
"inode_no": and the number? All of the other fields that are
preceded by a \t in the seq_printf() call have tabs in the output.
Except for the tabs vs. spaces, the Documentation change is:
Acked-by: Randy Dunlap <rdunlap@...radead.org>
> + 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..2c25909bf9d1 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\ninode_no:\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);
>
thanks.
--
~Randy
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