Messages in this thread | | | From | Pavel Tatashin <> | Date | Thu, 15 Jul 2021 14:57:37 -0400 | Subject | Re: [PATCH 1/2] mm: KSM: fix ksm_run data type |
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On Thu, Jul 15, 2021 at 2:30 PM Matthew Wilcox <willy@infradead.org> wrote: > > On Thu, Jul 15, 2021 at 02:21:21PM -0400, Pavel Tatashin wrote: > > On Thu, Jul 15, 2021 at 2:18 PM Matthew Wilcox <willy@infradead.org> wrote: > > > > > > On Fri, Jul 16, 2021 at 12:01:01AM +0600, Zhansaya Bagdauletkyzy wrote: > > > > +++ b/mm/ksm.c > > > > @@ -289,7 +289,7 @@ static int ksm_nr_node_ids = 1; > > > > #define KSM_RUN_MERGE 1 > > > > #define KSM_RUN_UNMERGE 2 > > > > #define KSM_RUN_OFFLINE 4 > > > > -static unsigned long ksm_run = KSM_RUN_STOP; > > > > +static unsigned int ksm_run = KSM_RUN_STOP; > > > > > > Should this be an enum instead? > > > > I think "unsigned int" is OK here, as it is exposed as uint to users: > > Documentation/ABI/testing/sysfs-kernel-mm-ksm > > > > /sys/kernel/mm/ksm/run > > > > run: write 0 to disable ksm, read 0 while ksm is disabled. > > > > - write 1 to run ksm, read 1 while ksm is running. > > - write 2 to disable ksm and unmerge all its pages. > > The document is out of date then as it does not mention 'offline'.
The offline mode cannot be set externally.
In run_store() if (flags > KSM_RUN_UNMERGE) return -EINVAL;
> > Also, why does the call to kstrtouint() specify base 10? If it is a > bitmap, then permitting 0x [1] is more natural. I would expect to see > base 0 there.
Users can only write 0, 1, or 2, it is not a bitmap from the user's perspective as the user cannot write: '3' . But, I think it is somewhat weird that ksm_run is used as a bitmap internally with KSM_RUN_OFFLINE = 4.
Imo, KSM_RUN_OFFLINE should be placed in a separate boolean from "ksm_run".
> > [1] or even 0b, although I see that _parse_integer_fixup_radix does not > support the 0b notation.
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