[PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Austin Kim]

If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
However, the bailout for mount is no longer proceeding.

For this reason, using WARN_ON rather than BUG() could prevent this situation.
---
 fs/xfs/xfs_mount.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 322da69..10fe000 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -213,8 +213,7 @@ xfs_initialize_perag(
 			goto out_hash_destroy;
 
 		spin_lock(&mp->m_perag_lock);
-		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
-			BUG();
+		if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
 			spin_unlock(&mp->m_perag_lock);
 			radix_tree_preload_end();
 			error = -EEXIST;
-- 
2.6.2

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Darrick J. Wong]

On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> However, the bailout for mount is no longer proceeding.
> 
> For this reason, using WARN_ON rather than BUG() could prevent this situation.
> ---
>  fs/xfs/xfs_mount.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 322da69..10fe000 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -213,8 +213,7 @@ xfs_initialize_perag(
>  			goto out_hash_destroy;
>  
>  		spin_lock(&mp->m_perag_lock);
> -		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> -			BUG();
> +		if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){

Need a space before the brace.

Will fix on import,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

>  			spin_unlock(&mp->m_perag_lock);
>  			radix_tree_preload_end();
>  			error = -EEXIST;
> -- 
> 2.6.2
> 

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Austin Kim]

Dear Mr. Darrick J. Wong

Thanks for reviewing patch. BTW, I have a question for you.

Do I have to update the patch again with 'a space before the brace'?
Or could I just wait for the patch to be imported?

It would be thankful if you give me a feedback.

BR,
Guillermo Austin Kim

2019년 8월 29일 (목) 오전 12:14, Darrick J. Wong <darrick.wong@oracle.com>님이 작성:
>
> On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> > If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> > However, the bailout for mount is no longer proceeding.
> >
> > For this reason, using WARN_ON rather than BUG() could prevent this situation.
> > ---
> >  fs/xfs/xfs_mount.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > index 322da69..10fe000 100644
> > --- a/fs/xfs/xfs_mount.c
> > +++ b/fs/xfs/xfs_mount.c
> > @@ -213,8 +213,7 @@ xfs_initialize_perag(
> >                       goto out_hash_destroy;
> >
> >               spin_lock(&mp->m_perag_lock);
> > -             if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> > -                     BUG();
> > +             if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
>
> Need a space before the brace.
>
> Will fix on import,
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
>
> --D
>
> >                       spin_unlock(&mp->m_perag_lock);
> >                       radix_tree_preload_end();
> >                       error = -EEXIST;
> > --
> > 2.6.2
> >

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Darrick J. Wong]

On Thu, Aug 29, 2019 at 06:30:43AM +0900, Austin Kim wrote:
> Dear Mr. Darrick J. Wong
> 
> Thanks for reviewing patch. BTW, I have a question for you.
> 
> Do I have to update the patch again with 'a space before the brace'?
> Or could I just wait for the patch to be imported?
> 
> It would be thankful if you give me a feedback.

I made the correction when I imported your patch into my testing tree,
so you don't need to resubmit the patch just to fix that one thing.

However, if you decide to send a new revision *for some other reason*,
then please make the correction in your own tree before resubmitting.

--D

> BR,
> Guillermo Austin Kim
> 
> 2019년 8월 29일 (목) 오전 12:14, Darrick J. Wong <darrick.wong@oracle.com>님이 작성:
> >
> > On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> > > If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> > > However, the bailout for mount is no longer proceeding.
> > >
> > > For this reason, using WARN_ON rather than BUG() could prevent this situation.
> > > ---
> > >  fs/xfs/xfs_mount.c | 3 +--
> > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > > index 322da69..10fe000 100644
> > > --- a/fs/xfs/xfs_mount.c
> > > +++ b/fs/xfs/xfs_mount.c
> > > @@ -213,8 +213,7 @@ xfs_initialize_perag(
> > >                       goto out_hash_destroy;
> > >
> > >               spin_lock(&mp->m_perag_lock);
> > > -             if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> > > -                     BUG();
> > > +             if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
> >
> > Need a space before the brace.
> >
> > Will fix on import,
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> >
> > --D
> >
> > >                       spin_unlock(&mp->m_perag_lock);
> > >                       radix_tree_preload_end();
> > >                       error = -EEXIST;
> > > --
> > > 2.6.2
> > >

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Christoph Hellwig]

On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> However, the bailout for mount is no longer proceeding.
> 
> For this reason, using WARN_ON rather than BUG() could prevent this situation.
> ---
>  fs/xfs/xfs_mount.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 322da69..10fe000 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -213,8 +213,7 @@ xfs_initialize_perag(
>  			goto out_hash_destroy;
>  
>  		spin_lock(&mp->m_perag_lock);
> -		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> -			BUG();
> +		if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){

Please make this a WARN_ON_ONCE so that we don't see a flodding of
messages in case of this error.

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Austin Kim]

2019년 8월 29일 (목) 오후 4:56, Christoph Hellwig <hch@infradead.org>님이 작성:
>
> On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> > If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> > However, the bailout for mount is no longer proceeding.
> >
> > For this reason, using WARN_ON rather than BUG() could prevent this situation.
> > ---
> >  fs/xfs/xfs_mount.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > index 322da69..10fe000 100644
> > --- a/fs/xfs/xfs_mount.c
> > +++ b/fs/xfs/xfs_mount.c
> > @@ -213,8 +213,7 @@ xfs_initialize_perag(
> >                       goto out_hash_destroy;
> >
> >               spin_lock(&mp->m_perag_lock);
> > -             if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> > -                     BUG();
> > +             if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
>
> Please make this a WARN_ON_ONCE so that we don't see a flodding of
> messages in case of this error.
>
Hello, Mr. Christoph
Thanks for good feedback.
If the kernel log is flooded with error message, as you pointed out,
it may cause other side-effect.(e.g: system non-responsive or lockup)

To. Mr. Darrick J. Wong
If you or other kernel developers do not disagree with the
idea(WARN_ON_ONCE instead of WARN_ON),
do I have to resend the patch with new revision?

The title, the commit message and patch might be changed as followings;
======
xfs: Use WARN_ON_ONCE rather than BUG() for bailout mount-operation

If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
However, the bailout for mount is no longer proceeding.

For this reason, using WARN_ON_ONCE rather than BUG() could prevent
this situation.

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 322da69..d831c13 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -213,8 +213,7 @@ xfs_initialize_perag(
                        goto out_hash_destroy;

                spin_lock(&mp->m_perag_lock);
-               if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
-                       BUG();
+               if (WARN_ON_ONCE(radix_tree_insert(&mp->m_perag_tree,
index, pag))) {
                        spin_unlock(&mp->m_perag_lock);
                        radix_tree_preload_end();
                        error = -EEXIST;
======

BR,
Guillermo Austin Kim

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Darrick J. Wong]

On Thu, Aug 29, 2019 at 09:59:17PM +0900, Austin Kim wrote:
> 2019년 8월 29일 (목) 오후 4:56, Christoph Hellwig <hch@infradead.org>님이 작성:
> >
> > On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> > > If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> > > However, the bailout for mount is no longer proceeding.
> > >
> > > For this reason, using WARN_ON rather than BUG() could prevent this situation.
> > > ---
> > >  fs/xfs/xfs_mount.c | 3 +--
> > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > > index 322da69..10fe000 100644
> > > --- a/fs/xfs/xfs_mount.c
> > > +++ b/fs/xfs/xfs_mount.c
> > > @@ -213,8 +213,7 @@ xfs_initialize_perag(
> > >                       goto out_hash_destroy;
> > >
> > >               spin_lock(&mp->m_perag_lock);
> > > -             if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> > > -                     BUG();
> > > +             if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
> >
> > Please make this a WARN_ON_ONCE so that we don't see a flodding of
> > messages in case of this error.
> >
> Hello, Mr. Christoph
> Thanks for good feedback.
> If the kernel log is flooded with error message, as you pointed out,
> it may cause other side-effect.(e.g: system non-responsive or lockup)
> 
> To. Mr. Darrick J. Wong
> If you or other kernel developers do not disagree with the
> idea(WARN_ON_ONCE instead of WARN_ON),
> do I have to resend the patch with new revision?

Yes, and please add your Signed-off-by in the new revision.

--D

> The title, the commit message and patch might be changed as followings;
> ======
> xfs: Use WARN_ON_ONCE rather than BUG() for bailout mount-operation
> 
> If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> However, the bailout for mount is no longer proceeding.
> 
> For this reason, using WARN_ON_ONCE rather than BUG() could prevent
> this situation.
> 
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 322da69..d831c13 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -213,8 +213,7 @@ xfs_initialize_perag(
>                         goto out_hash_destroy;
> 
>                 spin_lock(&mp->m_perag_lock);
> -               if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> -                       BUG();
> +               if (WARN_ON_ONCE(radix_tree_insert(&mp->m_perag_tree,
> index, pag))) {
>                         spin_unlock(&mp->m_perag_lock);
>                         radix_tree_preload_end();
>                         error = -EEXIST;
> ======
> 
> BR,
> Guillermo Austin Kim

Re: [PATCH] xfs: Use WARN_ON rather than BUG() for bailout mount-operation

[Darrick J. Wong]

On Thu, Aug 29, 2019 at 12:56:55AM -0700, Christoph Hellwig wrote:
> On Wed, Aug 28, 2019 at 03:47:49PM +0900, Austin Kim wrote:
> > If the CONFIG_BUG is enabled, BUG() is executed and then system is crashed.
> > However, the bailout for mount is no longer proceeding.
> > 
> > For this reason, using WARN_ON rather than BUG() could prevent this situation.
> > ---
> >  fs/xfs/xfs_mount.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > index 322da69..10fe000 100644
> > --- a/fs/xfs/xfs_mount.c
> > +++ b/fs/xfs/xfs_mount.c
> > @@ -213,8 +213,7 @@ xfs_initialize_perag(
> >  			goto out_hash_destroy;
> >  
> >  		spin_lock(&mp->m_perag_lock);
> > -		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> > -			BUG();
> > +		if (WARN_ON(radix_tree_insert(&mp->m_perag_tree, index, pag))){
> 
> Please make this a WARN_ON_ONCE so that we don't see a flodding of
> messages in case of this error.

How would it flood?  If the radix tree insertion fails we dump all the
pag structures and fail log recovery / mount / growfs.  I suppose if
one were out of memory and hammering the system hard with repeated mount
calls...

--D