[PATCH] docs: fault-injection: fix defaults

[PATCH] docs: fault-injection: fix defaults

[Dylan Yudaken]

ignore-gfp-wait and ignore-gfp-highmem defaults are actually true (Y) in
both failslab and fail_page_alloc, not false as the docs suggest. See
page_alloc.c:3762 and failslab.c:13

At the same time use 'Y' instead of '1' in the example scripts just for
consistency. (though 1 would work)

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 Documentation/fault-injection/fault-injection.rst | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
index 4a25c5eb6f07..8b4e1ce26d01 100644
--- a/Documentation/fault-injection/fault-injection.rst
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -132,7 +132,7 @@ configuration of fault-injection capabilities.
 
 	Format: { 'Y' | 'N' }
 
-	default is 'N', setting it to 'Y' won't inject failures into
+	default is 'Y', setting it to 'Y' won't inject failures into
 	highmem/user allocations.
 
 - /sys/kernel/debug/failslab/ignore-gfp-wait:
@@ -140,7 +140,7 @@ configuration of fault-injection capabilities.
 
 	Format: { 'Y' | 'N' }
 
-	default is 'N', setting it to 'Y' will inject failures
+	default is 'Y', setting it to 'Y' will inject failures
 	only into non-sleep allocations (GFP_ATOMIC allocations).
 
 - /sys/kernel/debug/fail_page_alloc/min-order:
@@ -280,7 +280,7 @@ Application Examples
     printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times
     echo 0 > /sys/kernel/debug/$FAILTYPE/space
     echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
-    echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
+    echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
 
     faulty_system()
     {
@@ -334,8 +334,8 @@ Application Examples
     printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times
     echo 0 > /sys/kernel/debug/$FAILTYPE/space
     echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
-    echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
-    echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem
+    echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
+    echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem
     echo 10 > /sys/kernel/debug/$FAILTYPE/stacktrace-depth
 
     trap "echo 0 > /sys/kernel/debug/$FAILTYPE/probability" SIGINT SIGTERM EXIT

base-commit: f443e374ae131c168a065ea1748feac6b2e76613
-- 
2.30.2

Re: [PATCH] docs: fault-injection: fix defaults

[Jonathan Corbet]

Dylan Yudaken <dylany@fb.com> writes:

> ignore-gfp-wait and ignore-gfp-highmem defaults are actually true (Y) in
> both failslab and fail_page_alloc, not false as the docs suggest. See
> page_alloc.c:3762 and failslab.c:13
>
> At the same time use 'Y' instead of '1' in the example scripts just for
> consistency. (though 1 would work)
>
> Signed-off-by: Dylan Yudaken <dylany@fb.com>
> ---
>  Documentation/fault-injection/fault-injection.rst | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
> index 4a25c5eb6f07..8b4e1ce26d01 100644
> --- a/Documentation/fault-injection/fault-injection.rst
> +++ b/Documentation/fault-injection/fault-injection.rst
> @@ -132,7 +132,7 @@ configuration of fault-injection capabilities.
>  
>  	Format: { 'Y' | 'N' }
>  
> -	default is 'N', setting it to 'Y' won't inject failures into
> +	default is 'Y', setting it to 'Y' won't inject failures into
>  	highmem/user allocations.

So the associated help text should perhaps have its sense changed too -
what happens if you set it to "N"?  The help text would be more useful,
IMO, if it read something like "set to 'N' if you want errors injected
into GFP_HIGHUSER allocations" (or whatever GFP flags actually apply
here). 

>  - /sys/kernel/debug/failslab/ignore-gfp-wait:
> @@ -140,7 +140,7 @@ configuration of fault-injection capabilities.
>  
>  	Format: { 'Y' | 'N' }
>  
> -	default is 'N', setting it to 'Y' will inject failures
> +	default is 'Y', setting it to 'Y' will inject failures
>  	only into non-sleep allocations (GFP_ATOMIC allocations).

This is a little better in general, but still would be improved by
telling the reader what they get if they change the default.

Thanks,

jon

Re: [PATCH] docs: fault-injection: fix defaults

[Dylan Yudaken]

On Fri, 2022-03-25 at 13:24 -0600, Jonathan Corbet wrote:
> Dylan Yudaken <dylany@fb.com> writes:
> 
> > ignore-gfp-wait and ignore-gfp-highmem defaults are actually true
> > (Y) in
> > both failslab and fail_page_alloc, not false as the docs suggest.
> > See
> > page_alloc.c:3762 and failslab.c:13
> > 
> > At the same time use 'Y' instead of '1' in the example scripts just
> > for
> > consistency. (though 1 would work)
> > 
> > Signed-off-by: Dylan Yudaken <dylany@fb.com>
> > ---
> >  Documentation/fault-injection/fault-injection.rst | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/Documentation/fault-injection/fault-injection.rst
> > b/Documentation/fault-injection/fault-injection.rst
> > index 4a25c5eb6f07..8b4e1ce26d01 100644
> > --- a/Documentation/fault-injection/fault-injection.rst
> > +++ b/Documentation/fault-injection/fault-injection.rst
> > @@ -132,7 +132,7 @@ configuration of fault-injection capabilities.
> >  
> >         Format: { 'Y' | 'N' }
> >  
> > -       default is 'N', setting it to 'Y' won't inject failures
> > into
> > +       default is 'Y', setting it to 'Y' won't inject failures
> > into
> >         highmem/user allocations.
> 
> So the associated help text should perhaps have its sense changed too
> -
> what happens if you set it to "N"?  The help text would be more
> useful,
> IMO, if it read something like "set to 'N' if you want errors
> injected
> into GFP_HIGHUSER allocations" (or whatever GFP flags actually apply
> here). 
> 
> >  - /sys/kernel/debug/failslab/ignore-gfp-wait:
> > @@ -140,7 +140,7 @@ configuration of fault-injection capabilities.
> >  
> >         Format: { 'Y' | 'N' }
> >  
> > -       default is 'N', setting it to 'Y' will inject failures
> > +       default is 'Y', setting it to 'Y' will inject failures
> >         only into non-sleep allocations (GFP_ATOMIC allocations).
> 
> This is a little better in general, but still would be improved by
> telling the reader what they get if they change the default.

Makes sense. I'll submit v2 with that but it might be a couple weeks
when I get time (and I first have to understand what they actually get
when changing the default).

> 
> Thanks,
> 
> jon