On Wed, 2020-12-09 at 07:13 +0100, Mike Galbraith wrote:
> On Wed, 2020-12-09 at 00:26 +0100, Vitaly Wool wrote:
> > Hi Mike,
> >
> > On 2020-12-07 16:41, Mike Galbraith wrote:
> > > On Mon, 2020-12-07 at 16:21 +0100, Vitaly Wool wrote:
> > >> On Mon, Dec 7, 2020 at 1:34 PM Mike Galbraith <efault@xxxxxx> wrote:
> > >>>
> > >>
> > >>> Unfortunately, that made zero difference.
> > >>
> > >> Okay, I suggest that you submit the patch that changes read_lock() to
> > >> write_lock() in __release_z3fold_page() and I'll ack it then.
> > >> I would like to rewrite the code so that write_lock is not necessary
> > >> there but I don't want to hold you back and it isn't likely that I'll
> > >> complete this today.
> > >
> > > Nah, I'm in no rush... especially not to sign off on "Because the
> > > little voices in my head said this bit should look like that bit over
> > > yonder, and testing _seems_ to indicate they're right about that" :)
> > >
> > > -Mike
> > >
> >
> > okay, thanks. Would this make things better:
>
> Yup, z3fold became RT tolerant with this (un-munged and) applied.
Below is the other change that any RT users of z3fold will need.
mm, z3fold: Remove preempt disabled sections for RT
Replace get_cpu_ptr() with migrate_disable()+this_cpu_ptr() so RT can take
spinlocks that become sleeping locks.
Signed-off-by Mike Galbraith <efault@xxxxxx>
---
mm/z3fold.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -617,14 +617,16 @@ static inline void add_to_unbuddied(stru
{
if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
zhdr->middle_chunks == 0) {
- struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
-
+ struct list_head *unbuddied;
int freechunks = num_free_chunks(zhdr);
+
+ migrate_disable();
+ unbuddied = this_cpu_ptr(pool->unbuddied);
spin_lock(&pool->lock);
list_add(&zhdr->buddy, &unbuddied[freechunks]);
spin_unlock(&pool->lock);
zhdr->cpu = smp_processor_id();
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
}
}
@@ -861,8 +863,9 @@ static inline struct z3fold_header *__z3
int chunks = size_to_chunks(size), i;
lookup:
+ migrate_disable();
/* First, try to find an unbuddied z3fold page. */
- unbuddied = get_cpu_ptr(pool->unbuddied);
+ unbuddied = this_cpu_ptr(pool->unbuddied);
for_each_unbuddied_list(i, chunks) {
struct list_head *l = &unbuddied[i];
@@ -880,7 +883,7 @@ static inline struct z3fold_header *__z3
!z3fold_page_trylock(zhdr)) {
spin_unlock(&pool->lock);
zhdr = NULL;
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
if (can_sleep)
cond_resched();
goto lookup;
@@ -894,7 +897,7 @@ static inline struct z3fold_header *__z3
test_bit(PAGE_CLAIMED, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
if (can_sleep)
cond_resched();
goto lookup;
@@ -909,7 +912,7 @@ static inline struct z3fold_header *__z3
kref_get(&zhdr->refcount);
break;
}
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
if (!zhdr) {
int cpu;
