On 10/30/2013 01:03 AM, Linus Torvalds wrote:
On Tue, Oct 29, 2013 at 12:27 PM, Raghavendra K T
<raghavendra.kt@xxxxxxxxxxxxxxxxxx> wrote:
Could one solution be cascading actual error
that is lost in fs/debugfs/inode.c:__create_file(), so that we could
take correct action in case of failure of debugfs_create_dir()?
(ugly side is we increase total number of params for __create_file to
6). or I hope there could be some better solution.
The solution to this would be to simply return an error-pointer. See
<linux/err.h>. That's what we do for most complex subsystems that
return a pointer to a struct: rather than returning "NULL" as an
error, return the actual error number encoded in the pointer itself.
Thank you Linus. Yes, this would have been ideal.
But that would require every user of debugfs_create_dir() to be
updated to check errors using IS_ERR() instead of checking against
NULL, and there's quite a few of them.
So I think just making the error be EEXIST is a simpler solution right now.
Agree.
I had below patch, and just before sending as formal mail I saw
Paolo's pull request which already took care of it.
---8<---
>From ac5d9f038c273f27bea7a54aab6af79b57f56317 Mon Sep 17 00:00:00 2001
From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Date: Wed, 30 Oct 2013 18:59:46 +0530
Subject: [PATCH] Return EEXIST on debugfs_create_dir failure in kvm
As quoted by Linus, EFAULT means "user passed in an invalid
virtual address pointer", which is why the error string is Bad address.
But when a debugfs directory creation fails, the above error is not valid.
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
I understand that Tim's patch that renames directory to something like
kvm-pv would solve kvm-amd/kvm-intel modules insertion problem.
This patch is to address error code change complained by Linus.
arch/x86/kernel/kvm.c | 2 +-
virt/kvm/kvm_main.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a0e2a8a..e475fdb 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -622,7 +622,7 @@ static int __init kvm_spinlock_debugfs(void)
d_kvm = kvm_init_debugfs();
if (d_kvm == NULL)
- return -ENOMEM;
+ return -EEXIST;
d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a9dd682..0430853 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3091,13 +3091,14 @@ static const struct file_operations *stat_fops[] = {
static int kvm_init_debug(void)
{
- int r = -EFAULT;
+ int r = -EEXIST;
struct kvm_stats_debugfs_item *p;
kvm_debugfs_dir = debugfs_create_dir("kvm", NULL);
if (kvm_debugfs_dir == NULL)
goto out;
+ r = -EFAULT;
for (p = debugfs_entries; p->name; ++p) {
p->dentry = debugfs_create_file(p->name, 0444, kvm_debugfs_dir,
(void *)(long)p->offset,
--
1.7.11.7
