| Message ID | 20220815010349.432313-3-haiyue.wang@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fix follow_page related issues | expand |
Haiyue Wang <haiyue.wang@intel.com> writes: > The page returned by follow_page with 'FOLL_GET' has get_page called, so Better to add "()" after function name to improve the readability, for example, "follow_page()". > it needs to call put_page for handling the reference count correctly. > > And as David reviewed, "device pages are never PageKsm pages". Drop this > zone device page check for break_ksm. > > Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages") In your patch description, I cannot find how the above commit is related to the bug you fixed. Add some words about that? Best Regards, Huang, Ying > Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> > --- > mm/huge_memory.c | 4 ++-- > mm/ksm.c | 12 +++++++++--- > mm/migrate.c | 10 +++++++--- > 3 files changed, 18 insertions(+), 8 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 8a7c1b344abe..b2ba17c3dcd7 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2963,10 +2963,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, > /* FOLL_DUMP to ignore special (like zero) pages */ > page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > > - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) > + if (IS_ERR_OR_NULL(page)) > continue; > > - if (!is_transparent_hugepage(page)) > + if (is_zone_device_page(page) || !is_transparent_hugepage(page)) > goto next; > > total++; > diff --git a/mm/ksm.c b/mm/ksm.c > index 42ab153335a2..e26f57fc1f0e 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr) > cond_resched(); > page = follow_page(vma, addr, > FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); > - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) > + if (IS_ERR_OR_NULL(page)) > break; > if (PageKsm(page)) > ret = handle_mm_fault(vma, addr, > @@ -560,12 +560,15 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item) > goto out; > > page = follow_page(vma, addr, FOLL_GET); > - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) > + if (IS_ERR_OR_NULL(page)) > goto out; > + if (is_zone_device_page(page)) > + goto out_putpage; > if (PageAnon(page)) { > flush_anon_page(vma, page, addr); > flush_dcache_page(page); > } else { > +out_putpage: > put_page(page); > out: > page = NULL; > @@ -2308,11 +2311,13 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) > if (ksm_test_exit(mm)) > break; > *page = follow_page(vma, ksm_scan.address, FOLL_GET); > - if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) { > + if (IS_ERR_OR_NULL(*page)) { > ksm_scan.address += PAGE_SIZE; > cond_resched(); > continue; > } > + if (is_zone_device_page(*page)) > + goto next_page; > if (PageAnon(*page)) { > flush_anon_page(vma, *page, ksm_scan.address); > flush_dcache_page(*page); > @@ -2327,6 +2332,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) > mmap_read_unlock(mm); > return rmap_item; > } > +next_page: > put_page(*page); > ksm_scan.address += PAGE_SIZE; > cond_resched(); > diff --git a/mm/migrate.c b/mm/migrate.c > index 581dfaad9257..fee12cd2f294 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1672,9 +1672,12 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, > goto out; > > err = -ENOENT; > - if (!page || is_zone_device_page(page)) > + if (!page) > goto out; > > + if (is_zone_device_page(page)) > + goto out_putpage; > + > err = 0; > if (page_to_nid(page) == node) > goto out_putpage; > @@ -1868,8 +1871,9 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > if (IS_ERR(page)) > goto set_status; > > - if (page && !is_zone_device_page(page)) { > - err = page_to_nid(page); > + if (page) { > + err = !is_zone_device_page(page) ? page_to_nid(page) > + : -ENOENT; > if (foll_flags & FOLL_GET) > put_page(page); > } else {
> -----Original Message----- > From: Huang, Ying <ying.huang@intel.com> > Sent: Monday, August 15, 2022 09:40 > To: Wang, Haiyue <haiyue.wang@intel.com> > Cc: linux-mm@kvack.org; linux-kernel@vger.kernel.org; akpm@linux-foundation.org; david@redhat.com; > linmiaohe@huawei.com; songmuchun@bytedance.com; naoya.horiguchi@linux.dev; alex.sierra@amd.com; Felix > Kuehling <Felix.Kuehling@amd.com>; Alistair Popple <apopple@nvidia.com> > Subject: Re: [PATCH v3 2/2] mm: fix the handling Non-LRU pages returned by follow_page > > Haiyue Wang <haiyue.wang@intel.com> writes: > > > The page returned by follow_page with 'FOLL_GET' has get_page called, so > > Better to add "()" after function name to improve the readability, for > example, "follow_page()". Got it, didn't notice this. ;-) > > > it needs to call put_page for handling the reference count correctly. > > > > And as David reviewed, "device pages are never PageKsm pages". Drop this > > zone device page check for break_ksm. > > > > Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages") > > In your patch description, I cannot find how the above commit is related > to the bug you fixed. Add some words about that? The first commit session, but maybe not very clear, will try to add more words In v4. > > Best Regards, > Huang, Ying > > > Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> > > --- > > mm/huge_memory.c | 4 ++-- > > mm/ksm.c | 12 +++++++++--- > > mm/migrate.c | 10 +++++++--- > > 3 files changed, 18 insertions(+), 8 deletions(-) > >
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8a7c1b344abe..b2ba17c3dcd7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2963,10 +2963,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, /* FOLL_DUMP to ignore special (like zero) pages */ page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) + if (IS_ERR_OR_NULL(page)) continue; - if (!is_transparent_hugepage(page)) + if (is_zone_device_page(page) || !is_transparent_hugepage(page)) goto next; total++; diff --git a/mm/ksm.c b/mm/ksm.c index 42ab153335a2..e26f57fc1f0e 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr) cond_resched(); page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) + if (IS_ERR_OR_NULL(page)) break; if (PageKsm(page)) ret = handle_mm_fault(vma, addr, @@ -560,12 +560,15 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item) goto out; page = follow_page(vma, addr, FOLL_GET); - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) + if (IS_ERR_OR_NULL(page)) goto out; + if (is_zone_device_page(page)) + goto out_putpage; if (PageAnon(page)) { flush_anon_page(vma, page, addr); flush_dcache_page(page); } else { +out_putpage: put_page(page); out: page = NULL; @@ -2308,11 +2311,13 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) if (ksm_test_exit(mm)) break; *page = follow_page(vma, ksm_scan.address, FOLL_GET); - if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) { + if (IS_ERR_OR_NULL(*page)) { ksm_scan.address += PAGE_SIZE; cond_resched(); continue; } + if (is_zone_device_page(*page)) + goto next_page; if (PageAnon(*page)) { flush_anon_page(vma, *page, ksm_scan.address); flush_dcache_page(*page); @@ -2327,6 +2332,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) mmap_read_unlock(mm); return rmap_item; } +next_page: put_page(*page); ksm_scan.address += PAGE_SIZE; cond_resched(); diff --git a/mm/migrate.c b/mm/migrate.c index 581dfaad9257..fee12cd2f294 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1672,9 +1672,12 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, goto out; err = -ENOENT; - if (!page || is_zone_device_page(page)) + if (!page) goto out; + if (is_zone_device_page(page)) + goto out_putpage; + err = 0; if (page_to_nid(page) == node) goto out_putpage; @@ -1868,8 +1871,9 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, if (IS_ERR(page)) goto set_status; - if (page && !is_zone_device_page(page)) { - err = page_to_nid(page); + if (page) { + err = !is_zone_device_page(page) ? page_to_nid(page) + : -ENOENT; if (foll_flags & FOLL_GET) put_page(page); } else {
The page returned by follow_page with 'FOLL_GET' has get_page called, so it needs to call put_page for handling the reference count correctly. And as David reviewed, "device pages are never PageKsm pages". Drop this zone device page check for break_ksm. Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages") Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> --- mm/huge_memory.c | 4 ++-- mm/ksm.c | 12 +++++++++--- mm/migrate.c | 10 +++++++--- 3 files changed, 18 insertions(+), 8 deletions(-)