On Sun, Aug 26, 2012 at 03:46:53AM +0100, Al Viro wrote:
>
> IMO doing that at open() time is just a headache for no good reason -
> resolving descriptor to struct file * at read() time as we do now
> is much saner. Better do that in your ->show(), since you are using
> a single-shot iterator anyway...
Al, the updated version is below. I suppose I can grab proc inode then
and lookup for file position and flags at show method. (I remember
what you've said about O_CLOEXEC bit, but I'll address this in
another patch).
---
From: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Subject: procfs: Convert /proc/pid/fdinfo/ handling routines to seq-file v3
This patch converts /proc/pid/fdinfo/ handling routines to seq-file which
is needed to extend seq operations and plug in auxiliary fdinfo provides
from subsystems like eventfd/eventpoll/fsnotify.
Note the proc_fd_link no longer call for proc_fd_info, simply because
proc_fd_info is converted to seq_fdinfo_open (which is seq-file open()
prototype).
v2 (by Al Viro):
- Don't use helper function with optional arguments, thus proc_fd_info get deprecated
- Use proc_fdinfo structure with seq_file embedded, thus we can use container_of helper
- Use fput to free reference to the file we've grabbed
v3 (by Al Viro):
- Don't grab struct file at read(2) time since it breaks ABI, instead all
manipulations should be done at ->show() call.
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Alexey Dobriyan <adobriyan@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: James Bottomley <jbottomley@xxxxxxxxxxxxx>
CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
CC: Alexey Dobriyan <adobriyan@xxxxxxxxx>
CC: Matthew Helsley <matt.helsley@xxxxxxxxx>
CC: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
---
fs/proc/fd.c | 142 +++++++++++++++++++++++++++++++++++++++--------------------
1 file changed, 95 insertions(+), 47 deletions(-)
Index: linux-2.6.git/fs/proc/fd.c
===================================================================
--- linux-2.6.git.orig/fs/proc/fd.c
+++ linux-2.6.git/fs/proc/fd.c
@@ -6,61 +6,100 @@
#include <linux/namei.h>
#include <linux/pid.h>
#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include "internal.h"
#include "fd.h"
-#define PROC_FDINFO_MAX 64
+struct proc_fdinfo {
+ struct seq_file m;
+ struct inode *inode;
+};
-static int proc_fd_info(struct inode *inode, struct path *path, char *info)
+static int seq_show(struct seq_file *m, void *v)
{
- struct task_struct *task = get_proc_task(inode);
+ struct proc_fdinfo *fdinfo = container_of(m, struct proc_fdinfo, m);
struct files_struct *files = NULL;
- int fd = proc_fd(inode);
- struct file *file;
+ int f_flags = 0, ret = -ENOENT;
+ struct file *file = NULL;
+ struct task_struct *task;
+
+ task = get_proc_task(fdinfo->inode);
+ if (!task)
+ return -ENOENT;
+
+ files = get_files_struct(task);
+ put_task_struct(task);
- if (task) {
- files = get_files_struct(task);
- put_task_struct(task);
- }
if (files) {
- /*
- * We are not taking a ref to the file structure, so we must
- * hold ->file_lock.
- */
+ int fd = proc_fd(fdinfo->inode);
+
spin_lock(&files->file_lock);
file = fcheck_files(files, fd);
if (file) {
- unsigned int f_flags;
- struct fdtable *fdt;
+ struct fdtable *fdt = files_fdtable(files);
- fdt = files_fdtable(files);
f_flags = file->f_flags & ~O_CLOEXEC;
if (close_on_exec(fd, fdt))
f_flags |= O_CLOEXEC;
- if (path) {
- *path = file->f_path;
- path_get(&file->f_path);
- }
- if (info)
- snprintf(info, PROC_FDINFO_MAX,
- "pos:\t%lli\n"
- "flags:\t0%o\n",
- (long long) file->f_pos,
- f_flags);
- spin_unlock(&files->file_lock);
- put_files_struct(files);
- return 0;
+ get_file(file);
+ ret = 0;
}
spin_unlock(&files->file_lock);
put_files_struct(files);
}
- return -ENOENT;
+
+ if (!ret) {
+ seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
+ (long long)file->f_pos, f_flags);
+ fput(file);
+ }
+
+ return ret;
+}
+
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+ struct proc_fdinfo *fdinfo;
+ int ret = 0;
+
+ fdinfo = kmalloc(sizeof(*fdinfo), GFP_KERNEL);
+ if (!fdinfo)
+ return -ENOMEM;
+
+ ihold(inode);
+ fdinfo->inode = inode;
+
+ file->private_data = &fdinfo->m;
+ ret = single_open(file, seq_show, NULL);
+ if (ret) {
+ iput(inode);
+ kfree(fdinfo);
+ }
+
+ return ret;
+}
+
+static int seq_fdinfo_release(struct inode *inode, struct file *file)
+{
+ struct proc_fdinfo *fdinfo =
+ container_of((struct seq_file *)file->private_data,
+ struct proc_fdinfo, m);
+ iput(fdinfo->inode);
+ return single_release(inode, file);
}
+static const struct file_operations proc_fdinfo_file_operations = {
+ .open = seq_fdinfo_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_fdinfo_release,
+};
+
static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
{
struct files_struct *files;
@@ -130,7 +169,32 @@ static const struct dentry_operations ti
static int proc_fd_link(struct dentry *dentry, struct path *path)
{
- return proc_fd_info(dentry->d_inode, path, NULL);
+ struct files_struct *files = NULL;
+ struct task_struct *task;
+ int ret = -ENOENT;
+
+ task = get_proc_task(dentry->d_inode);
+ if (task) {
+ files = get_files_struct(task);
+ put_task_struct(task);
+ }
+
+ if (files) {
+ int fd = proc_fd(dentry->d_inode);
+ struct file *fd_file;
+
+ spin_lock(&files->file_lock);
+ fd_file = fcheck_files(files, fd);
+ if (fd_file) {
+ *path = fd_file->f_path;
+ path_get(&fd_file->f_path);
+ ret = 0;
+ }
+ spin_unlock(&files->file_lock);
+ put_files_struct(files);
+ }
+
+ return ret;
}
static struct dentry *
@@ -245,22 +309,6 @@ out_no_task:
return retval;
}
-static ssize_t proc_fdinfo_read(struct file *file, char __user *buf,
- size_t len, loff_t *ppos)
-{
- char tmp[PROC_FDINFO_MAX];
- int err = proc_fd_info(file->f_path.dentry->d_inode, NULL, tmp);
- if (!err)
- err = simple_read_from_buffer(buf, len, ppos, tmp, strlen(tmp));
- return err;
-}
-
-static const struct file_operations proc_fdinfo_file_operations = {
- .open = nonseekable_open,
- .read = proc_fdinfo_read,
- .llseek = no_llseek,
-};
-
static int proc_readfd(struct file *filp, void *dirent, filldir_t filldir)
{
return proc_readfd_common(filp, dirent, filldir, proc_fd_instantiate);
--
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