From: Danny Feng <dfeng@redhat.com>
Date: Tue, 2 Feb 2010 08:34:19 -0500
Subject: [fs] proc: make errno values consistent when race occurs
Message-id: <20100202083431.32257.9907.sendpatchset@dhcp-65-180.nay.redhat.com>
Patchwork-id: 23086
O-Subject: [PATCH RHEL5.5 BZ556545] procfs: make errno values consistent when
	open pident vs exit(2) race occurs
Bugzilla: 556545
RH-Acked-by: Oleg Nesterov <oleg@redhat.com>
RH-Acked-by: Jarod Wilson <jarod@redhat.com>
RH-Acked-by: Amerigo Wang <amwang@redhat.com>

RHBZ#:
https://bugzilla.redhat.com/show_bug.cgi?id=556545

Description:
The open(/proc/PID/xxx) system call fails with EINVAL errno if the PID process
is exiting at the same time, even though it should be ENOENT.

upstream status:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=bd6daba909d8484bd2ccf6017db4028d7a420927

commit 444ceed extracts some codes in proc_pident_lookup to proc_pident_instantiate. Back to proc_pident_lookup in rhel5
kernel, error is already assigned to ERR_PTR(-ENOENT) before changed to -EINVAL, so removing the EINVAL code will fix the
problem for rhel5

KABI:
no breakage is found

Brew Build:
https://brewweb.devel.redhat.com/taskinfo?taskID=2238630

Test status:
The reproducer runs forever, never break with "open(/proc/PID/stat) failed with errno: 22"

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 5f94ca7..6e1e6c0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1954,7 +1954,6 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
 	if (!p->name)
 		goto out;
 
-	error = ERR_PTR(-EINVAL);
 	inode = proc_pid_make_inode(dir->i_sb, task, p->type);
 	if (!inode)
 		goto out;