Messages in this thread Patch in this message | | | Date | Wed, 30 Oct 2013 19:31:05 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH 3.12-rc7] KVM: Fix modprobe failure for kvm_intel/kvm_amd |
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On 10/30/2013 01:03 AM, Linus Torvalds wrote: > On Tue, Oct 29, 2013 at 12:27 PM, Raghavendra K T > <raghavendra.kt@linux.vnet.ibm.com> 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@linux.vnet.ibm.com> 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@linux.vnet.ibm.com> --- 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
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