[PATCH v2 1/2] procfs: Add 'size' to /proc/<pid>/fdinfo/

[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 at google.com>
Reviewed-by: Christian König <christian.koenig at amd.com>
---

Changes in v2:
  - Add Christian's Reviewed-by

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);
-- 
2.37.0.rc0.161.g10f37bed90-goog