linux-kernel - [PATCH 17/23] proc: Teach /proc/<pid>/fd to use file_hotplug

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Date:	Mon,  1 Jun 2009 14:50:42 -0700
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-fsdevel@...r.kernel.org>,
	Hugh Dickins <hugh@...itas.com>, Tejun Heo <tj@...nel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Eric W. Biederman" <ebiederm@...well.arastra.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: [PATCH 17/23] proc: Teach /proc/<pid>/fd to use file_hotplug_lock

From: Eric W. Biederman <ebiederm@...well.arastra.com>

I have taken the opportunity to modify proc_fd_info to have
a single exit point.

Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
---
 fs/proc/base.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index fb45615..ee4cdc2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1626,6 +1626,7 @@ static int proc_fd_info(struct inode *inode, struct path *path, char *info)
 	struct files_struct *files = NULL;
 	struct file *file;
 	int fd = proc_fd(inode);
+	int retval = -ENOENT;
 
 	if (task) {
 		files = get_files_struct(task);
@@ -1639,24 +1640,26 @@ static int proc_fd_info(struct inode *inode, struct path *path, char *info)
 		spin_lock(&files->file_lock);
 		file = fcheck_files(files, fd);
 		if (file) {
-			if (path) {
-				*path = file->f_path;
-				path_get(&file->f_path);
+			retval = -EIO;
+			if (file_hotplug_read_trylock(file)) {
+				retval = 0;
+				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,
+						file->f_flags);
+				file_hotplug_read_unlock(file);
 			}
-			if (info)
-				snprintf(info, PROC_FDINFO_MAX,
-					 "pos:\t%lli\n"
-					 "flags:\t0%o\n",
-					 (long long) file->f_pos,
-					 file->f_flags);
-			spin_unlock(&files->file_lock);
-			put_files_struct(files);
-			return 0;
 		}
 		spin_unlock(&files->file_lock);
 		put_files_struct(files);
 	}
-	return -ENOENT;
+	return retval;
 }
 
 static int proc_fd_link(struct inode *inode, struct path *path)
-- 
1.6.3.1.54.g99dd.dirty

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