| Message ID | 20190715164705.220693-1-henryburns@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/z3fold.c: Reinitialize zhdr structs after migration | expand |
On Mon, Jul 15, 2019 at 9:47 AM Henry Burns <henryburns@google.com> wrote: > > z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE). > However, zhdr contains fields that can't be directly coppied over (ex: > list_head, a circular linked list). We only need to initialize the > linked lists in new_zhdr, as z3fold_isolate_page() already ensures > that these lists are empty. > > Additionally it is possible that zhdr->work has been placed in a > workqueue. In this case we shouldn't migrate the page, as zhdr->work > references zhdr as opposed to new_zhdr. > > Fixes: bba4c5f96ce4 ("mm/z3fold.c: support page migration") > Signed-off-by: Henry Burns <henryburns@google.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> > --- > mm/z3fold.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 42ef9955117c..9da471bcab93 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -1352,12 +1352,22 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa > z3fold_page_unlock(zhdr); > return -EBUSY; > } > + if (work_pending(&zhdr->work)) { > + z3fold_page_unlock(zhdr); > + return -EAGAIN; > + } > new_zhdr = page_address(newpage); > memcpy(new_zhdr, zhdr, PAGE_SIZE); > newpage->private = page->private; > page->private = 0; > z3fold_page_unlock(zhdr); > spin_lock_init(&new_zhdr->page_lock); > + INIT_WORK(&new_zhdr->work, compact_page_work); > + /* > + * z3fold_page_isolate() ensures that this list is empty, so we only > + * have to reinitialize it. > + */ > + INIT_LIST_HEAD(&new_zhdr->buddy); > new_mapping = page_mapping(page); > __ClearPageMovable(page); > ClearPagePrivate(page); > -- > 2.22.0.510.g264f2c817a-goog >
Den mån 15 juli 2019 6:47 emHenry Burns <henryburns@google.com> skrev: > z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE). > However, zhdr contains fields that can't be directly coppied over (ex: > list_head, a circular linked list). We only need to initialize the > linked lists in new_zhdr, as z3fold_isolate_page() already ensures > that these lists are empty. > > Additionally it is possible that zhdr->work has been placed in a > workqueue. In this case we shouldn't migrate the page, as zhdr->work > references zhdr as opposed to new_zhdr. > > Fixes: bba4c5f96ce4 ("mm/z3fold.c: support page migration") > Signed-off-by: Henry Burns <henryburns@google.com> > --- > mm/z3fold.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 42ef9955117c..9da471bcab93 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -1352,12 +1352,22 @@ static int z3fold_page_migrate(struct > address_space *mapping, struct page *newpa > z3fold_page_unlock(zhdr); > return -EBUSY; > } > + if (work_pending(&zhdr->work)) { > + z3fold_page_unlock(zhdr); > + return -EAGAIN; > + } > new_zhdr = page_address(newpage); > memcpy(new_zhdr, zhdr, PAGE_SIZE); > newpage->private = page->private; > page->private = 0; > z3fold_page_unlock(zhdr); > spin_lock_init(&new_zhdr->page_lock); > + INIT_WORK(&new_zhdr->work, compact_page_work); > + /* > + * z3fold_page_isolate() ensures that this list is empty, so we > only > + * have to reinitialize it. > + */ > On the nitpicking side, we seem to have ensured that directly in migrate :) Looks OK to me otherwise. ~Vitaly + INIT_LIST_HEAD(&new_zhdr->buddy); > new_mapping = page_mapping(page); > __ClearPageMovable(page); > ClearPagePrivate(page); > -- > 2.22.0.510.g264f2c817a-goog > >
>> >> z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE). >> However, zhdr contains fields that can't be directly coppied over (ex: >> list_head, a circular linked list). We only need to initialize the >> linked lists in new_zhdr, as z3fold_isolate_page() already ensures >> that these lists are empty. >> >> Additionally it is possible that zhdr->work has been placed in a >> workqueue. In this case we shouldn't migrate the page, as zhdr->work >> references zhdr as opposed to new_zhdr. >> >> Fixes: bba4c5f96ce4 ("mm/z3fold.c: support page migration") >> Signed-off-by: Henry Burns <henryburns@google.com> >> --- >> mm/z3fold.c | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/mm/z3fold.c b/mm/z3fold.c >> index 42ef9955117c..9da471bcab93 100644 >> --- a/mm/z3fold.c >> +++ b/mm/z3fold.c >> @@ -1352,12 +1352,22 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa >> z3fold_page_unlock(zhdr); >> return -EBUSY; >> } >> + if (work_pending(&zhdr->work)) { >> + z3fold_page_unlock(zhdr); >> + return -EAGAIN; >> + } >> new_zhdr = page_address(newpage); >> memcpy(new_zhdr, zhdr, PAGE_SIZE); >> newpage->private = page->private; >> page->private = 0; >> z3fold_page_unlock(zhdr); >> spin_lock_init(&new_zhdr->page_lock); >> + INIT_WORK(&new_zhdr->work, compact_page_work); >> + /* >> + * z3fold_page_isolate() ensures that this list is empty, so we only >> + * have to reinitialize it. >> + */ > > > On the nitpicking side, we seem to have ensured that directly in migrate :) Looks OK to me otherwise. Ok, I see it happens in the call to do_compact_page(). Got it, new patch coming out now. > > ~Vitaly > >> + INIT_LIST_HEAD(&new_zhdr->buddy); >> new_mapping = page_mapping(page); >> __ClearPageMovable(page); >> ClearPagePrivate(page); >> -- >> 2.22.0.510.g264f2c817a-goog >>
Sorry Vitaly, I had the wrong impression from your email that
INIT_LIST_HEAD() was being ensured directly in migrate and got
confused. (I thought you were saying it happened through the call to
do_compact_page() queued).
That being said, I don't see where in migrate new_zhdr->buddy is being
checked. We do check for new_zhdr.work with
if (work_pending(&zhdr->work)) {
...
}
Is that what you were referring to?
diff --git a/mm/z3fold.c b/mm/z3fold.c index 42ef9955117c..9da471bcab93 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -1352,12 +1352,22 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa z3fold_page_unlock(zhdr); return -EBUSY; } + if (work_pending(&zhdr->work)) { + z3fold_page_unlock(zhdr); + return -EAGAIN; + } new_zhdr = page_address(newpage); memcpy(new_zhdr, zhdr, PAGE_SIZE); newpage->private = page->private; page->private = 0; z3fold_page_unlock(zhdr); spin_lock_init(&new_zhdr->page_lock); + INIT_WORK(&new_zhdr->work, compact_page_work); + /* + * z3fold_page_isolate() ensures that this list is empty, so we only + * have to reinitialize it. + */ + INIT_LIST_HEAD(&new_zhdr->buddy); new_mapping = page_mapping(page); __ClearPageMovable(page); ClearPagePrivate(page);
z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE). However, zhdr contains fields that can't be directly coppied over (ex: list_head, a circular linked list). We only need to initialize the linked lists in new_zhdr, as z3fold_isolate_page() already ensures that these lists are empty. Additionally it is possible that zhdr->work has been placed in a workqueue. In this case we shouldn't migrate the page, as zhdr->work references zhdr as opposed to new_zhdr. Fixes: bba4c5f96ce4 ("mm/z3fold.c: support page migration") Signed-off-by: Henry Burns <henryburns@google.com> --- mm/z3fold.c | 10 ++++++++++ 1 file changed, 10 insertions(+)