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SubjectRe: [PATCH] proc: extend /proc/<pid>/fdinfo/<fd>
Hi Miklos,

<quote sender="Miklos Szeredi">
> On Sat, 2008-02-09 at 20:01 +0800, Eugene Teo wrote:
> > This patch extends /proc/<pid>/fdinfo/<fd> to report information about open
> > files, and pathname. This information can be useful to know when debugging an
> > application.
> >
> > For each file descriptor, the information is provided in the following format:
> >
> > kerndev: ~/code/kernel# cat /proc/`pgrep pickup`/fdinfo/6
> > mode: 0622
> > dev: 253,0
> > ino: 21463057
>
> These are already available via 'stat /proc/<pid>/fd/<fd>'
>
> > uid: 89
> > gid: 89
>
> AFAICS file->f_[ug]id are only used by the netfilter code, but I guess
> it wouldn't hurt to show them here. But please add fields at the end of
> the file, instead of the beggining.

Ok, will do.

> > rdev: 0,0
>
> This is in struct stat too.
>
> > pos: 0
> > flags: 04002 FD_CLOEXEC # if close-on-exec flag is set
>
> FD_CLOEXEC should be on a separate line, because it's not an O_FOO flag.
> > path: /var/spool/postfix/public/pickup
>
> readlink /proc/<pid>/fd/<fd>

Thanks for the review. I agree that some of the information can be omitted
since it can be accessed using stat and readlink. I still think it is useful
to have ino in the output though.

Here's the updated patch:

[PATCH] proc: extend /proc/<pid>/fdinfo/<fd>

This patch extends /proc/<pid>/fdinfo/<fd> to report information about open
files, and pathname. This information can be useful to know when debugging an
application.

For each file descriptor, the information is provided in the following format:

kerndev: ~/code/kernel$ cat /proc/`pgrep firefox-bin`/fdinfo/29
pos: 49152
flags: 02
uid: 500
gid: 500
ino: 13205793
fd_flags: FD_CLOEXEC # if close-on-exec flag is set

Signed-off-by: Eugene Teo <eugeneteo@kernel.sg>
---
fs/proc/base.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c59852b..5ea5dee 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1402,7 +1402,7 @@ out:
return ~0U;
}

-#define PROC_FDINFO_MAX 64
+#define PROC_FDINFO_MAX 128

static int proc_fd_info(struct inode *inode, struct dentry **dentry,
struct vfsmount **mnt, char *info)
@@ -1428,12 +1428,26 @@ static int proc_fd_info(struct inode *inode, struct dentry **dentry,
*mnt = mntget(file->f_path.mnt);
if (dentry)
*dentry = dget(file->f_path.dentry);
- if (info)
+ /* called by proc_fdinfo_read() */
+ if (info) {
+ struct fdtable *fdt = files_fdtable(files);
+ struct dentry *d = dget(file->f_path.dentry);
+ int gcoe = FD_ISSET(fd, fdt->close_on_exec);
+
snprintf(info, PROC_FDINFO_MAX,
"pos:\t%lli\n"
- "flags:\t0%o\n",
+ "flags:\t0%o\n"
+ "uid:\t%d\n"
+ "gid:\t%d\n"
+ "ino:\t%ld\n"
+ "fd_flags:\t%s\n",
(long long) file->f_pos,
- file->f_flags);
+ file->f_flags,
+ file->f_uid, file->f_gid,
+ d->d_inode->i_ino,
+ gcoe ? "FD_CLOEXEC" : "0");
+ dput(d);
+ }
spin_unlock(&files->file_lock);
put_files_struct(files);
return 0;


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