| Message ID | 20220711084948.274787-6-ying.huang@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [-V2,1/7] migrate: fix syscall move_pages() return value for failure | expand |
On Mon, Jul 11, 2022 at 04:49:46PM +0800, Huang Ying wrote: > If THP or hugetlbfs page migration isn't supported, unmap_and_move() > or unmap_and_move_huge_page() will return -ENOSYS. For THP, splitting > will be tried, but if splitting doesn't succeed, the THP will be left > in "from" list wrongly. If some other pages are retried, the THP > migration failure will counted again. This is fixed via moving the > failure THP from "from" to "ret_pages". > > Another issue of the original code is that the unsupported failure > processing isn't consistent between THP and hugetlbfs page. Make them > consistent in this patch to make the code easier to be understood too. > > Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages") > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > Cc: Zi Yan <ziy@nvidia.com> > Cc: Yang Shi <shy828301@gmail.com> > --- > mm/migrate.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4bceba143db0..8cce73b7c046 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1192,10 +1192,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > * tables or check whether the hugepage is pmd-based or not before > * kicking migration. > */ > - if (!hugepage_migration_supported(page_hstate(hpage))) { > - list_move_tail(&hpage->lru, ret); > + if (!hugepage_migration_supported(page_hstate(hpage))) > return -ENOSYS; > - } > > if (page_count(hpage) == 1) { > /* page was freed from under us. So we are done. */ > @@ -1392,6 +1390,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > * page will be put back > * -EAGAIN: stay on the from list > * -ENOMEM: stay on the from list > + * -ENOSYS: stay on the from list > * Other errno: put on ret_pages list then splice to > * from list > */ > @@ -1421,6 +1420,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > } > > nr_failed_pages += nr_subpages; > + list_move_tail(&page->lru, &ret_pages); I must be missing something, but migrate_pages() calls unmap_and_move_huge_page() with ret being ret_pages, so list_move_tail(&hpage->lru, ret) == list_move_tail(&page->lru, &ret_pages) Yet, you say "This is fixed via moving the failure THP from "from" to "ret_pages"". /me confused.
Oscar Salvador <osalvador@suse.de> writes: > On Mon, Jul 11, 2022 at 04:49:46PM +0800, Huang Ying wrote: >> If THP or hugetlbfs page migration isn't supported, unmap_and_move() >> or unmap_and_move_huge_page() will return -ENOSYS. For THP, splitting >> will be tried, but if splitting doesn't succeed, the THP will be left >> in "from" list wrongly. If some other pages are retried, the THP >> migration failure will counted again. This is fixed via moving the >> failure THP from "from" to "ret_pages". >> >> Another issue of the original code is that the unsupported failure >> processing isn't consistent between THP and hugetlbfs page. Make them >> consistent in this patch to make the code easier to be understood too. >> >> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> >> Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages") >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> Cc: Zi Yan <ziy@nvidia.com> >> Cc: Yang Shi <shy828301@gmail.com> >> --- >> mm/migrate.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 4bceba143db0..8cce73b7c046 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1192,10 +1192,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, >> * tables or check whether the hugepage is pmd-based or not before >> * kicking migration. >> */ >> - if (!hugepage_migration_supported(page_hstate(hpage))) { >> - list_move_tail(&hpage->lru, ret); >> + if (!hugepage_migration_supported(page_hstate(hpage))) >> return -ENOSYS; >> - } >> >> if (page_count(hpage) == 1) { >> /* page was freed from under us. So we are done. */ >> @@ -1392,6 +1390,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> * page will be put back >> * -EAGAIN: stay on the from list >> * -ENOMEM: stay on the from list >> + * -ENOSYS: stay on the from list >> * Other errno: put on ret_pages list then splice to >> * from list >> */ >> @@ -1421,6 +1420,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> } >> >> nr_failed_pages += nr_subpages; >> + list_move_tail(&page->lru, &ret_pages); > > I must be missing something, but migrate_pages() calls unmap_and_move_huge_page() > with ret being ret_pages, so > > list_move_tail(&hpage->lru, ret) == list_move_tail(&page->lru, &ret_pages) > > Yet, you say "This is fixed via moving the failure THP from "from" to "ret_pages"". > /me confused. To make it consistent between hugetlb page and THP/normal page, I have revised the unmap_and_move_huge_page() via deleting the list_move_tail() there for ENOSYS. After that, we move the hugetlb page and THP/normal page in the same way in migrate_pages(). Best Regards, Huang, Ying
diff --git a/mm/migrate.c b/mm/migrate.c index 4bceba143db0..8cce73b7c046 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1192,10 +1192,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, * tables or check whether the hugepage is pmd-based or not before * kicking migration. */ - if (!hugepage_migration_supported(page_hstate(hpage))) { - list_move_tail(&hpage->lru, ret); + if (!hugepage_migration_supported(page_hstate(hpage))) return -ENOSYS; - } if (page_count(hpage) == 1) { /* page was freed from under us. So we are done. */ @@ -1392,6 +1390,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, * page will be put back * -EAGAIN: stay on the from list * -ENOMEM: stay on the from list + * -ENOSYS: stay on the from list * Other errno: put on ret_pages list then splice to * from list */ @@ -1421,6 +1420,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, } nr_failed_pages += nr_subpages; + list_move_tail(&page->lru, &ret_pages); break; case -ENOMEM: /*