linux-kernel - Re: [RFC PATCH] procfs: Add file path and size to /proc/<pid>/fdinfo

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Date:   Thu, 19 May 2022 14:46:51 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kalesh Singh <kaleshsingh@...gle.com>
Cc:     ilkos@...gle.com, tjmercier@...gle.com, surenb@...gle.com,
        kernel-team@...roid.com, Jonathan Corbet <corbet@....net>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Anton Mitterer <mail@...istoph.anton.mitterer.name>,
        Kees Cook <keescook@...omium.org>,
        Mike Rapoport <rppt@...nel.org>,
        Colin Cross <ccross@...gle.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [RFC PATCH] procfs: Add file path and size to /proc/<pid>/fdinfo

Hi--

On 5/19/22 14:40, Kalesh Singh wrote:
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 061744c436d9..ad66d78aca51 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -1922,13 +1922,16 @@ 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 four fields -- 'pos', 'flags', 'mnt_id' and 'ino'.
> +files have at least six fields -- 'pos', 'flags', 'mnt_id', 'ino', 'size',
> +and 'path'.
> +
>  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.
> +the file, 'size' represents the size of the file in bytes, and 'path'
> +represents the file path.
>  
>  A typical output is::
>  
> @@ -1936,6 +1939,8 @@ A typical output is::
>  	flags:	0100002
>  	mnt_id:	19
>  	ino:	63107
> +        size:   0
> +        path:   /dev/null
>  
>  All locks associated with a file descriptor are shown in its fdinfo too::
>  
> @@ -1953,6 +1958,8 @@ Eventfd files
>  	flags:	04002
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:[eventfd]
>  	eventfd-count:	5a
>  
>  where 'eventfd-count' is hex value of a counter.
> @@ -1966,6 +1973,8 @@ Signalfd files
>  	flags:	04002
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:[signalfd]
>  	sigmask:	0000000000000200
>  
>  where 'sigmask' is hex value of the signal mask associated
> @@ -1980,6 +1989,8 @@ Epoll files
>  	flags:	02
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:[eventpoll]
>  	tfd:        5 events:       1d data: ffffffffffffffff pos:0 ino:61af sdev:7
>  
>  where 'tfd' is a target file descriptor number in decimal form,
> @@ -1998,6 +2009,8 @@ For inotify files the format is the following::
>  	flags:	02000000
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:inotify
>  	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
> @@ -2021,6 +2034,8 @@ For fanotify files the format is::
>  	flags:	02
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:[fanotify]
>  	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
> @@ -2046,6 +2061,8 @@ Timerfd files
>  	flags:	02
>  	mnt_id:	9
>  	ino:	63107
> +        size:   0
> +        path:   anon_inode:[timerfd]
>  	clockid: 0
>  	ticks: 0
>  	settime flags: 01
> @@ -2070,6 +2087,7 @@ DMA Buffer files
>  	mnt_id:	9
>  	ino:	63107
>  	size:   32768
> +        path:   /dmabuf:
>  	count:  2
>  	exp_name:  system-heap

All of these added lines should be indented with a tab instead of spaces.

thanks.
-- 
~Randy