Re: [PATCH 1/2] procfs: Add 'size' to /proc/<pid>/fdinfo/

[Christian König <christian.koenig@xxxxxxx>]

Am 31.05.22 um 23:25 schrieb Kalesh Singh:
> To be able to account the amount of memory a process is keeping pinned
> by open file descriptors add a 'size' field to fdinfo output.
>
> dmabufs fds already expose a 'size' field for this reason, remove this
> and make it a common field for all fds. This allows tracking of
> other types of memory (e.g. memfd and ashmem in Android).
>
> Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>

At least for the DMA-buf part feel free to add an Reviewed-by: Christian 
König <christian.koenig@xxxxxxx> for this.

Regards,
Christian.

> ---
>
> Changes from rfc:
>    - Split adding 'size' and 'path' into a separate patches, per Christian
>    - Split fdinfo seq_printf into separate lines, per Christian
>    - Fix indentation (use tabs) in documentaion, per Randy
>
>   Documentation/filesystems/proc.rst | 12 ++++++++++--
>   drivers/dma-buf/dma-buf.c          |  1 -
>   fs/proc/fd.c                       |  9 +++++----
>   3 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 1bc91fb8c321..779c05528e87 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -1886,13 +1886,14 @@ 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 five fields -- 'pos', 'flags', 'mnt_id', 'ino', and 'size'.
> +
>   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, and 'size' represents the size of the file in bytes.
>   
>   A typical output is::
>   
> @@ -1900,6 +1901,7 @@ A typical output is::
>   	flags:	0100002
>   	mnt_id:	19
>   	ino:	63107
> +	size:	0
>   
>   All locks associated with a file descriptor are shown in its fdinfo too::
>   
> @@ -1917,6 +1919,7 @@ Eventfd files
>   	flags:	04002
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	eventfd-count:	5a
>   
>   where 'eventfd-count' is hex value of a counter.
> @@ -1930,6 +1933,7 @@ Signalfd files
>   	flags:	04002
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	sigmask:	0000000000000200
>   
>   where 'sigmask' is hex value of the signal mask associated
> @@ -1944,6 +1948,7 @@ Epoll files
>   	flags:	02
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	tfd:        5 events:       1d data: ffffffffffffffff pos:0 ino:61af sdev:7
>   
>   where 'tfd' is a target file descriptor number in decimal form,
> @@ -1962,6 +1967,7 @@ For inotify files the format is the following::
>   	flags:	02000000
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	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
> @@ -1985,6 +1991,7 @@ For fanotify files the format is::
>   	flags:	02
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	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
> @@ -2010,6 +2017,7 @@ Timerfd files
>   	flags:	02
>   	mnt_id:	9
>   	ino:	63107
> +	size:   0
>   	clockid: 0
>   	ticks: 0
>   	settime flags: 01
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 32f55640890c..5f2ae38c960f 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -378,7 +378,6 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
>   {
>   	struct dma_buf *dmabuf = file->private_data;
>   
> -	seq_printf(m, "size:\t%zu\n", dmabuf->size);
>   	/* Don't count the temporary reference taken inside procfs seq_show */
>   	seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
>   	seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
> diff --git a/fs/proc/fd.c b/fs/proc/fd.c
> index 913bef0d2a36..464bc3f55759 100644
> --- a/fs/proc/fd.c
> +++ b/fs/proc/fd.c
> @@ -54,10 +54,11 @@ 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\nino:\t%lu\n",
> -		   (long long)file->f_pos, f_flags,
> -		   real_mount(file->f_path.mnt)->mnt_id,
> -		   file_inode(file)->i_ino);
> +	seq_printf(m, "pos:\t%lli\n", (long long)file->f_pos);
> +	seq_printf(m, "flags:\t0%o\n", f_flags);
> +	seq_printf(m, "mnt_id:\t%i\n", real_mount(file->f_path.mnt)->mnt_id);
> +	seq_printf(m, "ino:\t%lu\n", file_inode(file)->i_ino);
> +	seq_printf(m, "size:\t%lli\n", (long long)file_inode(file)->i_size);
>   
>   	/* show_fd_locks() never deferences files so a stale value is safe */
>   	show_fd_locks(m, file, files);