[PATCH] ext4: add a line break for proc mb_groups display

[PATCH] ext4: add a line break for proc mb_groups display

[Huaitong Han]

This patch adds a line break for proc mb_groups display.

Signed-off-by: Huaitong Han <huaitong.han@intel.com>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 61eaf74..4424b7b 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2285,7 +2285,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
 	if (group == 0)
 		seq_puts(seq, "#group: free  frags first ["
 			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
-			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
+			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]\n");
 
 	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
 		sizeof(struct ext4_group_info);
-- 
2.4.3

Re: [PATCH] ext4: add a line break for proc mb_groups display

[Darrick J. Wong]

On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
> This patch adds a line break for proc mb_groups display.
> 
> Signed-off-by: Huaitong Han <huaitong.han@intel.com>
> ---
>  fs/ext4/mballoc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 61eaf74..4424b7b 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2285,7 +2285,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
>  	if (group == 0)
>  		seq_puts(seq, "#group: free  frags first ["
>  			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
> -			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
> +			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]\n");

Oh, heh.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

>  
>  	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
>  		sizeof(struct ext4_group_info);
> -- 
> 2.4.3
> 
> --
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Re: [PATCH] ext4: add a line break for proc mb_groups display

[Joe Perches]

On Wed, 2016-02-03 at 10:13 -0800, Darrick J. Wong wrote:
> On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
> > This patch adds a line break for proc mb_groups display.

Using 2 lines for output might break any existing users.

Are there any?

> > 
> > Signed-off-by: Huaitong Han <huaitong.han@intel.com>
> > ---
> >  fs/ext4/mballoc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> > index 61eaf74..4424b7b 100644
> > --- a/fs/ext4/mballoc.c
> > +++ b/fs/ext4/mballoc.c
> > @@ -2285,7 +2285,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
> >  	if (group == 0)
> >  		seq_puts(seq, "#group: free  frags first ["
> >  			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
> > -			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
> > +			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]\n");
> 
> Oh, heh.
> 
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> 
> --D
> 
> >  
> >  	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
> >  		sizeof(struct ext4_group_info);

Re: [PATCH] ext4: add a line break for proc mb_groups display

[Darrick J. Wong]

On Wed, Feb 03, 2016 at 10:30:32AM -0800, Joe Perches wrote:
> On Wed, 2016-02-03 at 10:13 -0800, Darrick J. Wong wrote:
> > On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
> > > This patch adds a line break for proc mb_groups display.
> 
> Using 2 lines for output might break any existing users.
> 
> Are there any?

It's a multiline file if you have more than one blockgroup; this just makes it
so that you don't have to special-case BG 0.

IOW: mb_groups scripts already had to parse multiple lines, and most likely any
script parsing it would inject a newline after the header.

--D

> 
> > > 
> > > Signed-off-by: Huaitong Han <huaitong.han@intel.com>
> > > ---
> > >  fs/ext4/mballoc.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> > > index 61eaf74..4424b7b 100644
> > > --- a/fs/ext4/mballoc.c
> > > +++ b/fs/ext4/mballoc.c
> > > @@ -2285,7 +2285,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
> > >  	if (group == 0)
> > >  		seq_puts(seq, "#group: free  frags first ["
> > >  			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
> > > -			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
> > > +			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]\n");
> > 
> > Oh, heh.
> > 
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > --D
> > 
> > >  
> > >  	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
> > >  		sizeof(struct ext4_group_info);
> 
> --
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Re: [PATCH] ext4: add a line break for proc mb_groups display

[Joe Perches]

On Wed, 2016-02-03 at 11:32 -0800, Darrick J. Wong wrote:
> On Wed, Feb 03, 2016 at 10:30:32AM -0800, Joe Perches wrote:
> > On Wed, 2016-02-03 at 10:13 -0800, Darrick J. Wong wrote:
> > > On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
> > > > This patch adds a line break for proc mb_groups display.
> > 
> > Using 2 lines for output might break any existing users.
> > 
> > Are there any?
> 
> It's a multiline file if you have more than one blockgroup; this just makes it
> so that you don't have to special-case BG 0.

And existing scripts might do that now and might fail
to do properly after this change.

> IOW: mb_groups scripts already had to parse multiple lines, and most likely any
> script parsing it would inject a newline after the header.

I've no dog in this fight really.  I just wanted to make
it clear that this could cause existing scripts to fail.

proc output is supposed to be unchanging except maybe
adding new fields to existing lines.

Your choice.

cheers, Joe

Re: [PATCH] ext4: add a line break for proc mb_groups display

[Darrick J. Wong]

On Wed, Feb 03, 2016 at 11:38:33AM -0800, Joe Perches wrote:
> On Wed, 2016-02-03 at 11:32 -0800, Darrick J. Wong wrote:
> > On Wed, Feb 03, 2016 at 10:30:32AM -0800, Joe Perches wrote:
> > > On Wed, 2016-02-03 at 10:13 -0800, Darrick J. Wong wrote:
> > > > On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
> > > > > This patch adds a line break for proc mb_groups display.
> > > 
> > > Using 2 lines for output might break any existing users.
> > > 
> > > Are there any?
> > 
> > It's a multiline file if you have more than one blockgroup; this just makes it
> > so that you don't have to special-case BG 0.
> 
> And existing scripts might do that now and might fail
> to do properly after this change.

Or they might have sed -e 's/]#0/]\n#0/g' in which case they won't be affected.

> > IOW: mb_groups scripts already had to parse multiple lines, and most likely any
> > script parsing it would inject a newline after the header.
> 
> I've no dog in this fight really.  I just wanted to make
> it clear that this could cause existing scripts to fail.
> 
> proc output is supposed to be unchanging except maybe
> adding new fields to existing lines.
> 
> Your choice.

Ted's, really.  I have no idea which scripts do with various per-fs /proc
files.  Usually poking in mb_groups is only done as part of failure report data
collection to see what's mucked up the fs this time.

Anyway, I'll defer to the maintainer. :)

--D

> 
> cheers, Joe
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Re: [PATCH] ext4: add a line break for proc mb_groups display

[Andreas Dilger]

[-- Attachment #1: Type: text/plain, Size: 2000 bytes --]

On Feb 3, 2016, at 1:07 PM, Darrick J. Wong <darrick.wong@oracle.com> wrote:
> 
> On Wed, Feb 03, 2016 at 11:38:33AM -0800, Joe Perches wrote:
>> On Wed, 2016-02-03 at 11:32 -0800, Darrick J. Wong wrote:
>>> On Wed, Feb 03, 2016 at 10:30:32AM -0800, Joe Perches wrote:
>>>> On Wed, 2016-02-03 at 10:13 -0800, Darrick J. Wong wrote:
>>>>> On Wed, Feb 03, 2016 at 09:19:06PM +0800, Huaitong Han wrote:
>>>>>> This patch adds a line break for proc mb_groups display.
>>>> 
>>>> Using 2 lines for output might break any existing users.
>>>> 
>>>> Are there any?
>>> 
>>> It's a multiline file if you have more than one blockgroup; this just makes it
>>> so that you don't have to special-case BG 0.
>> 
>> And existing scripts might do that now and might fail
>> to do properly after this change.
> 
> Or they might have sed -e 's/]#0/]\n#0/g' in which case they won't be affected.

I suspect that any scripts which handled this in the past probably didn't
even notice and just missed the bg=0 line at the end of the header.  Users
looking at the output probably saw it line-wrapped by the terminal and
didn't notice either.

>>> IOW: mb_groups scripts already had to parse multiple lines, and most likely any
>>> script parsing it would inject a newline after the header.
>> 
>> I've no dog in this fight really.  I just wanted to make
>> it clear that this could cause existing scripts to fail.
>> 
>> proc output is supposed to be unchanging except maybe
>> adding new fields to existing lines.
>> 
>> Your choice.
> 
> Ted's, really.  I have no idea which scripts do with various per-fs /proc
> files.  Usually poking in mb_groups is only done as part of failure report data
> collection to see what's mucked up the fs this time.
> 
> Anyway, I'll defer to the maintainer. :)

I think it makes sense to accept the patch, since I doubt any scripts will be broken, and it is the "right thing to do" rather than perpetuate a bug.

Cheers, Andreas






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Re: [PATCH] ext4: add a line break for proc mb_groups display

[Joe Perches]

On Wed, 2016-02-03 at 14:12 -0700, Andreas Dilger wrote:

> I think it makes sense to accept the patch, since I doubt any scripts
> will be broken, and it is the "right thing to do" rather than
> perpetuate a bug.

Perhaps it also would make sense to add some text
to the commit log about this.

Re: [PATCH] ext4: add a line break for proc mb_groups display

[Andreas Dilger]

[-- Attachment #1: Type: text/plain, Size: 988 bytes --]


> On Feb 3, 2016, at 6:19 AM, Huaitong Han <huaitong.han@intel.com> wrote:
> 
> This patch adds a line break for proc mb_groups display.
> 
> Signed-off-by: Huaitong Han <huaitong.han@intel.com>

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> fs/ext4/mballoc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 61eaf74..4424b7b 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2285,7 +2285,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
> 	if (group == 0)
> 		seq_puts(seq, "#group: free  frags first ["
> 			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
> -			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
> +			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]\n");
> 
> 	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
> 		sizeof(struct ext4_group_info);
> --
> 2.4.3
> 


Cheers, Andreas






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Re: [PATCH] ext4: add a line break for proc mb_groups display

[Theodore Ts'o]

On Wed, Feb 03, 2016 at 02:12:44PM -0700, Andreas Dilger wrote:
> 
> > On Feb 3, 2016, at 6:19 AM, Huaitong Han <huaitong.han@intel.com> wrote:
> > 
> > This patch adds a line break for proc mb_groups display.
> > 
> > Signed-off-by: Huaitong Han <huaitong.han@intel.com>
> 
> Reviewed-by: Andreas Dilger <adilger@dilger.ca>

Thanks, applied.

					- Ted