mbox series

[v2,0/4] Change the return value for page isolation functions

Message ID cover.1676382188.git.baolin.wang@linux.alibaba.com
Headers
Series Change the return value for page isolation functions |

Message

Baolin Wang Feb. 14, 2023, 1:59 p.m. UTC 
  Now the page isolation functions did not return a boolean to indicate
success or not, instead it will return a negative error when failed
to isolate a page. So below code used in most places seem a boolean
success/failure thing, which can confuse people whether the isolation
is successful.

if (folio_isolate_lru(folio))
        continue;

Moreover the page isolation functions only return 0 or -EBUSY, and
most users did not care about the negative error except for few users,
thus we can convert all page isolation functions to return a boolean
value, which can remove the confusion to make code more clear.

No functional changes intended in this patch series.

Changes from v1:
 - Convert all isolation functions to return bool.

Baolin Wang (4):
  mm: change to return bool for folio_isolate_lru()
  mm: change to return bool for isolate_lru_page()
  mm: hugetlb: change to return bool for isolate_hugetlb()
  mm: change to return bool for isolate_movable_page()

 include/linux/hugetlb.h |  6 +++---
 include/linux/migrate.h |  6 +++---
 mm/compaction.c         |  2 +-
 mm/damon/paddr.c        |  2 +-
 mm/folio-compat.c       |  4 ++--
 mm/gup.c                |  2 +-
 mm/hugetlb.c            | 12 ++++++++----
 mm/internal.h           |  4 ++--
 mm/khugepaged.c         |  4 ++--
 mm/madvise.c            |  4 ++--
 mm/memcontrol.c         |  4 ++--
 mm/memory-failure.c     | 10 +++++-----
 mm/memory_hotplug.c     |  2 +-
 mm/mempolicy.c          |  4 ++--
 mm/migrate.c            | 17 ++++++++++-------
 mm/migrate_device.c     |  2 +-
 mm/vmscan.c             | 10 +++++-----
 17 files changed, 51 insertions(+), 44 deletions(-)

Comments

David Hildenbrand Feb. 14, 2023, 5:52 p.m. UTC | #1 
On 14.02.23 14:59, Baolin Wang wrote:
> Now the page isolation functions did not return a boolean to indicate
> success or not, instead it will return a negative error when failed
> to isolate a page. So below code used in most places seem a boolean
> success/failure thing, which can confuse people whether the isolation
> is successful.
> 
> if (folio_isolate_lru(folio))
>          continue;
> 
> Moreover the page isolation functions only return 0 or -EBUSY, and
> most users did not care about the negative error except for few users,
> thus we can convert all page isolation functions to return a boolean
> value, which can remove the confusion to make code more clear.
> 
> No functional changes intended in this patch series.
> 
> Changes from v1:
>   - Convert all isolation functions to return bool.

Acked-by: David Hildenbrand <david@redhat.com>

Although it's controversial if

if (!ret)
	ret = -EBUSY;
else
	ret = 0;

is really appealing to the readers eye :)

ret = ret ? 0 : -EBUSY;

It's still confusing.

would be better as

ret = isolated ? 0 : -EBUSY;

IOW, not reusing the "int ret" variable.
Baolin Wang Feb. 15, 2023, 1:21 a.m. UTC | #2 
On 2/15/2023 1:52 AM, David Hildenbrand wrote:
> On 14.02.23 14:59, Baolin Wang wrote:
>> Now the page isolation functions did not return a boolean to indicate
>> success or not, instead it will return a negative error when failed
>> to isolate a page. So below code used in most places seem a boolean
>> success/failure thing, which can confuse people whether the isolation
>> is successful.
>>
>> if (folio_isolate_lru(folio))
>>          continue;
>>
>> Moreover the page isolation functions only return 0 or -EBUSY, and
>> most users did not care about the negative error except for few users,
>> thus we can convert all page isolation functions to return a boolean
>> value, which can remove the confusion to make code more clear.
>>
>> No functional changes intended in this patch series.
>>
>> Changes from v1:
>>   - Convert all isolation functions to return bool.
> 
> Acked-by: David Hildenbrand <david@redhat.com>

Thanks.

> 
> Although it's controversial if
> 
> if (!ret)
>      ret = -EBUSY;
> else
>      ret = 0;
> 
> is really appealing to the readers eye :)
> 
> ret = ret ? 0 : -EBUSY;
> 
> It's still confusing.
> 
> would be better as
> 
> ret = isolated ? 0 : -EBUSY;
> 
> IOW, not reusing the "int ret" variable.

Yes, pretty clear. Will do in next version.