[PATCH] common/rc: cleanup old .kmemleak files

[PATCH] common/rc: cleanup old .kmemleak files

[Luís Henriques]

I've spent a non-negligible amount of time looking into a kmemleak that
didn't exist in the code I was testing because there was an old .kmemleak
file in the results directory.  I don't think this is an intended behaviour,
so I'm proposing to remove these files everytime we capture the result of a
new scan.

Signed-off-by: Luís Henriques <lhenriques@suse.de>
---
 common/rc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/common/rc b/common/rc
index 741579af82d2..6aa6be704e51 100644
--- a/common/rc
+++ b/common/rc
@@ -4433,6 +4433,8 @@ _capture_kmemleak()
 	local kern_knob="$DEBUGFS_MNT/kmemleak"
 	local leak_file="$1"
 
+	rm -f "$leak_file"
+
 	# Tell the kernel to scan for memory leaks.  Apparently the write
 	# returns before the scan is complete, so do it twice in the hopes
 	# that twice is enough to capture all the leaks.

Re: [PATCH] common/rc: cleanup old .kmemleak files

[Darrick J. Wong]

On Wed, Jul 12, 2023 at 03:51:01PM +0100, Luís Henriques wrote:
> I've spent a non-negligible amount of time looking into a kmemleak that
> didn't exist in the code I was testing because there was an old .kmemleak
> file in the results directory.  I don't think this is an intended behaviour,
> so I'm proposing to remove these files everytime we capture the result of a
> new scan.
> 
> Signed-off-by: Luís Henriques <lhenriques@suse.de>
> ---
>  common/rc | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/common/rc b/common/rc
> index 741579af82d2..6aa6be704e51 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -4433,6 +4433,8 @@ _capture_kmemleak()
>  	local kern_knob="$DEBUGFS_MNT/kmemleak"
>  	local leak_file="$1"
>  
> +	rm -f "$leak_file"

Some callers of this helper specify a device file when all they want to
do is clear the old kmemleak report data:

$ git grep -w _capture_kmemleak
common/rc:4490:_capture_kmemleak()
common/rc:4535:         _capture_kmemleak /dev/null
common/rc:4555:         _capture_kmemleak /dev/null
common/rc:4560: _capture_kmemleak "$leak_file"

The simplest fix here I think would be:

	# Some callers pass in /dev/null when they want to clear the
	# kernel's leak report file and do not care what was in that.
	test -f "$leak_file" && rm -f "$leak_file"

--D

> +
>  	# Tell the kernel to scan for memory leaks.  Apparently the write
>  	# returns before the scan is complete, so do it twice in the hopes
>  	# that twice is enough to capture all the leaks.

[PATCH v2] common/rc: cleanup old .kmemleak files

[Luís Henriques]

I've spent a non-negligible amount of time looking into a kmemleak that
didn't exist in the code I was testing because there was an old .kmemleak
file in the results directory.  I don't think this is an intended behaviour,
so I'm proposing to remove these files everytime we capture the result of a
new scan.

Signed-off-by: Luís Henriques <lhenriques@suse.de>
---
 common/rc | 2 ++
 1 file changed, 2 insertions(+)

Changes since v1:
I realised that _capture_kmemleak() is called with /dev/null as argument, so
this version is probably better.

diff --git a/common/rc b/common/rc
index 741579af82d2..6850889e815e 100644
--- a/common/rc
+++ b/common/rc
@@ -4433,6 +4433,8 @@ _capture_kmemleak()
 	local kern_knob="$DEBUGFS_MNT/kmemleak"
 	local leak_file="$1"
 
+	[ -f "$leak_file" ] && rm -f "$leak_file"
+
 	# Tell the kernel to scan for memory leaks.  Apparently the write
 	# returns before the scan is complete, so do it twice in the hopes
 	# that twice is enough to capture all the leaks.

Re: [PATCH v2] common/rc: cleanup old .kmemleak files

[Darrick J. Wong]

On Wed, Jul 12, 2023 at 05:35:00PM +0100, Luís Henriques wrote:
> I've spent a non-negligible amount of time looking into a kmemleak that
> didn't exist in the code I was testing because there was an old .kmemleak
> file in the results directory.  I don't think this is an intended behaviour,
> so I'm proposing to remove these files everytime we capture the result of a
> new scan.
> 
> Signed-off-by: Luís Henriques <lhenriques@suse.de>
> ---
>  common/rc | 2 ++
>  1 file changed, 2 insertions(+)
> 
> Changes since v1:
> I realised that _capture_kmemleak() is called with /dev/null as argument, so
> this version is probably better.
> 
> diff --git a/common/rc b/common/rc
> index 741579af82d2..6850889e815e 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -4433,6 +4433,8 @@ _capture_kmemleak()
>  	local kern_knob="$DEBUGFS_MNT/kmemleak"
>  	local leak_file="$1"
>  
> +	[ -f "$leak_file" ] && rm -f "$leak_file"

I was hoping you'd incorporate the comment explaining why the test uses
-f and not -e.

--D

> +
>  	# Tell the kernel to scan for memory leaks.  Apparently the write
>  	# returns before the scan is complete, so do it twice in the hopes
>  	# that twice is enough to capture all the leaks.

Re: [PATCH v2] common/rc: cleanup old .kmemleak files

[Luís Henriques]

"Darrick J. Wong" <djwong@kernel.org> writes:

> On Wed, Jul 12, 2023 at 05:35:00PM +0100, Luís Henriques wrote:
>> I've spent a non-negligible amount of time looking into a kmemleak that
>> didn't exist in the code I was testing because there was an old .kmemleak
>> file in the results directory.  I don't think this is an intended behaviour,
>> so I'm proposing to remove these files everytime we capture the result of a
>> new scan.
>> 
>> Signed-off-by: Luís Henriques <lhenriques@suse.de>
>> ---
>>  common/rc | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> Changes since v1:
>> I realised that _capture_kmemleak() is called with /dev/null as argument, so
>> this version is probably better.
>> 
>> diff --git a/common/rc b/common/rc
>> index 741579af82d2..6850889e815e 100644
>> --- a/common/rc
>> +++ b/common/rc
>> @@ -4433,6 +4433,8 @@ _capture_kmemleak()
>>  	local kern_knob="$DEBUGFS_MNT/kmemleak"
>>  	local leak_file="$1"
>>  
>> +	[ -f "$leak_file" ] && rm -f "$leak_file"
>
> I was hoping you'd incorporate the comment explaining why the test uses
> -f and not -e.

You're right.  The reason I didn't was because I sent out v2 before seeing
your email.  Anyway, I'll send out v3 in a second.  And thanks for the
review, by the way!

Cheers,
-- 
Luís

>
> --D
>
>> +
>>  	# Tell the kernel to scan for memory leaks.  Apparently the write
>>  	# returns before the scan is complete, so do it twice in the hopes
>>  	# that twice is enough to capture all the leaks.

Re: [PATCH v2] common/rc: cleanup old .kmemleak files

[Darrick J. Wong]

On Thu, Jul 13, 2023 at 09:23:32AM +0100, Luís Henriques wrote:
> "Darrick J. Wong" <djwong@kernel.org> writes:
> 
> > On Wed, Jul 12, 2023 at 05:35:00PM +0100, Luís Henriques wrote:
> >> I've spent a non-negligible amount of time looking into a kmemleak that
> >> didn't exist in the code I was testing because there was an old .kmemleak
> >> file in the results directory.  I don't think this is an intended behaviour,
> >> so I'm proposing to remove these files everytime we capture the result of a
> >> new scan.
> >> 
> >> Signed-off-by: Luís Henriques <lhenriques@suse.de>
> >> ---
> >>  common/rc | 2 ++
> >>  1 file changed, 2 insertions(+)
> >> 
> >> Changes since v1:
> >> I realised that _capture_kmemleak() is called with /dev/null as argument, so
> >> this version is probably better.
> >> 
> >> diff --git a/common/rc b/common/rc
> >> index 741579af82d2..6850889e815e 100644
> >> --- a/common/rc
> >> +++ b/common/rc
> >> @@ -4433,6 +4433,8 @@ _capture_kmemleak()
> >>  	local kern_knob="$DEBUGFS_MNT/kmemleak"
> >>  	local leak_file="$1"
> >>  
> >> +	[ -f "$leak_file" ] && rm -f "$leak_file"
> >
> > I was hoping you'd incorporate the comment explaining why the test uses
> > -f and not -e.
> 
> You're right.  The reason I didn't was because I sent out v2 before seeing
> your email.  Anyway, I'll send out v3 in a second.  And thanks for the
> review, by the way!

aha, ok.

--D

> Cheers,
> -- 
> Luís
> 
> >
> > --D
> >
> >> +
> >>  	# Tell the kernel to scan for memory leaks.  Apparently the write
> >>  	# returns before the scan is complete, so do it twice in the hopes
> >>  	# that twice is enough to capture all the leaks.