* [PATCH] mm: mlockall error for flag MCL_ONFAULT
@ 2019-05-22 11:23 Potyra, Stefan
2019-05-24 21:43 ` Daniel Jordan
0 siblings, 1 reply; 5+ messages in thread
From: Potyra, Stefan @ 2019-05-22 11:23 UTC (permalink / raw)
To: linux-mm, linux-kernel; +Cc: Potyra, Stefan, Jordan, Tobias
If mlockall() is called with only MCL_ONFAULT as flag,
it removes any previously applied lockings and does
nothing else.
This behavior is counter-intuitive and doesn't match the
Linux man page.
Consequently, return the error EINVAL, if only MCL_ONFAULT
is passed. That way, applications will at least detect that
they are calling mlockall() incorrectly.
Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage")
Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
---
Sparse shows a warning for mlock.c, but it is not related to
this patch.
mm/mlock.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/mlock.c b/mm/mlock.c
index e492a155c51a..03f39cbdd4c4 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -797,7 +797,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
unsigned long lock_limit;
int ret;
- if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
+ if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
+ flags == MCL_ONFAULT)
return -EINVAL;
if (!can_do_mlock())
--
2.20.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] mm: mlockall error for flag MCL_ONFAULT
2019-05-22 11:23 [PATCH] mm: mlockall error for flag MCL_ONFAULT Potyra, Stefan
@ 2019-05-24 21:43 ` Daniel Jordan
2019-05-27 7:04 ` Michal Hocko
0 siblings, 1 reply; 5+ messages in thread
From: Daniel Jordan @ 2019-05-24 21:43 UTC (permalink / raw)
To: Potyra, Stefan
Cc: linux-mm, linux-kernel, Jordan, Tobias, akpm, vbabka, mhocko,
kirill.shutemov, linux-api
[ Adding linux-api and some of the people who were involved in the
MCL_ONFAULT/mlock2/etc discussions. Author of the Fixes patch appears to
have moved on. ]
On Wed, May 22, 2019 at 11:23:37AM +0000, Potyra, Stefan wrote:
> If mlockall() is called with only MCL_ONFAULT as flag,
> it removes any previously applied lockings and does
> nothing else.
The change looks reasonable. Hard to imagine any application relies on it, and
they really shouldn't be if they are. Debian codesearch turned up only a few
cases where stress-ng was doing this for unknown reasons[1] and this change
isn't gonna break those. In this case I think changing the syscall's behavior
is justified.
> This behavior is counter-intuitive and doesn't match the
> Linux man page.
I'd quote it for the changelog:
For mlockall():
EINVAL Unknown flags were specified or MCL_ONFAULT was specified with‐
out either MCL_FUTURE or MCL_CURRENT.
With that you can add
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
[1] https://sources.debian.org/src/stress-ng/0.09.50-1/stress-mlock.c/?hl=203#L203
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm: mlockall error for flag MCL_ONFAULT
2019-05-24 21:43 ` Daniel Jordan
@ 2019-05-27 7:04 ` Michal Hocko
2019-05-27 7:53 ` [PATCH v2] " Potyra, Stefan
0 siblings, 1 reply; 5+ messages in thread
From: Michal Hocko @ 2019-05-27 7:04 UTC (permalink / raw)
To: Daniel Jordan
Cc: Potyra, Stefan, linux-mm, linux-kernel, Jordan, Tobias, akpm,
vbabka, kirill.shutemov, linux-api
On Fri 24-05-19 17:43:04, Daniel Jordan wrote:
> [ Adding linux-api and some of the people who were involved in the
> MCL_ONFAULT/mlock2/etc discussions. Author of the Fixes patch appears to
> have moved on. ]
>
> On Wed, May 22, 2019 at 11:23:37AM +0000, Potyra, Stefan wrote:
> > If mlockall() is called with only MCL_ONFAULT as flag,
> > it removes any previously applied lockings and does
> > nothing else.
>
> The change looks reasonable. Hard to imagine any application relies on it, and
> they really shouldn't be if they are. Debian codesearch turned up only a few
> cases where stress-ng was doing this for unknown reasons[1] and this change
> isn't gonna break those. In this case I think changing the syscall's behavior
> is justified.
>
> > This behavior is counter-intuitive and doesn't match the
> > Linux man page.
>
> I'd quote it for the changelog:
>
> For mlockall():
>
> EINVAL Unknown flags were specified or MCL_ONFAULT was specified with‐
> out either MCL_FUTURE or MCL_CURRENT.
>
> With that you can add
>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
>
> [1] https://sources.debian.org/src/stress-ng/0.09.50-1/stress-mlock.c/?hl=203#L203
Well spotted and the fix looks reasonable as well. Quoting the man page
seems useful as well.
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] mm: mlockall error for flag MCL_ONFAULT
2019-05-27 7:04 ` Michal Hocko
@ 2019-05-27 7:53 ` Potyra, Stefan
2019-05-27 13:19 ` Vlastimil Babka
0 siblings, 1 reply; 5+ messages in thread
From: Potyra, Stefan @ 2019-05-27 7:53 UTC (permalink / raw)
To: Michal Hocko, Daniel Jordan
Cc: Potyra, Stefan, linux-mm, linux-kernel, Jordan, Tobias, akpm,
vbabka, kirill.shutemov, linux-api
If mlockall() is called with only MCL_ONFAULT as flag,
it removes any previously applied lockings and does
nothing else.
This behavior is counter-intuitive and doesn't match the
Linux man page.
For mlockall():
EINVAL Unknown flags were specified or MCL_ONFAULT was specified with‐
out either MCL_FUTURE or MCL_CURRENT.
Consequently, return the error EINVAL, if only MCL_ONFAULT
is passed. That way, applications will at least detect that
they are calling mlockall() incorrectly.
Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage")
Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
mm/mlock.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/mlock.c b/mm/mlock.c
index e492a155c51a..03f39cbdd4c4 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -797,7 +797,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
unsigned long lock_limit;
int ret;
- if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
+ if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
+ flags == MCL_ONFAULT)
return -EINVAL;
if (!can_do_mlock())
--
2.20.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm: mlockall error for flag MCL_ONFAULT
2019-05-27 7:53 ` [PATCH v2] " Potyra, Stefan
@ 2019-05-27 13:19 ` Vlastimil Babka
0 siblings, 0 replies; 5+ messages in thread
From: Vlastimil Babka @ 2019-05-27 13:19 UTC (permalink / raw)
To: Potyra, Stefan, Michal Hocko, Daniel Jordan
Cc: linux-mm, linux-kernel, Jordan, Tobias, akpm, kirill.shutemov, linux-api
On 5/27/19 9:53 AM, Potyra, Stefan wrote:
> If mlockall() is called with only MCL_ONFAULT as flag,
> it removes any previously applied lockings and does
> nothing else.
>
> This behavior is counter-intuitive and doesn't match the
> Linux man page.
>
> For mlockall():
>
> EINVAL Unknown flags were specified or MCL_ONFAULT was specified with‐
> out either MCL_FUTURE or MCL_CURRENT.
>
> Consequently, return the error EINVAL, if only MCL_ONFAULT
> is passed. That way, applications will at least detect that
> they are calling mlockall() incorrectly.
>
> Fixes: b0f205c2a308 ("mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage")
> Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Thanks, shame we didn't catch it during review. Hope nobody will report
a regression.
> ---
> mm/mlock.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mlock.c b/mm/mlock.c
> index e492a155c51a..03f39cbdd4c4 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -797,7 +797,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
> unsigned long lock_limit;
> int ret;
>
> - if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
> + if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
> + flags == MCL_ONFAULT)
> return -EINVAL;
>
> if (!can_do_mlock())
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-05-27 13:19 UTC | newest]
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2019-05-22 11:23 [PATCH] mm: mlockall error for flag MCL_ONFAULT Potyra, Stefan
2019-05-24 21:43 ` Daniel Jordan
2019-05-27 7:04 ` Michal Hocko
2019-05-27 7:53 ` [PATCH v2] " Potyra, Stefan
2019-05-27 13:19 ` Vlastimil Babka
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