| Message ID | 20220429064051.61552-8-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | A few fixup patches for z3fold | expand |
On Fri, Apr 29, 2022 at 8:40 AM Miaohe Lin <linmiaohe@huawei.com> wrote: > > Think about the below race window: > > CPU1 CPU2 > z3fold_reclaim_page z3fold_free > test_and_set_bit PAGE_CLAIMED > failed to reclaim page > z3fold_page_lock(zhdr); > add back to the lru list; > z3fold_page_unlock(zhdr); > get_z3fold_header > page_claimed=test_and_set_bit PAGE_CLAIMED > > clear_bit(PAGE_CLAIMED, &page->private); > > if (!page_claimed) /* it's false true */ > free_handle is not called > > free_handle won't be called in this case. So z3fold_buddy_slots will leak. > Fix it by always clear PAGE_CLAIMED under z3fold page lock. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > mm/z3fold.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index a1c150fc8def..4a3cd2ff15b0 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -1221,8 +1221,8 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) > return; > } > if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { > - put_z3fold_header(zhdr); > clear_bit(PAGE_CLAIMED, &page->private); > + put_z3fold_header(zhdr); > return; > } > if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { > @@ -1424,8 +1424,8 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) > spin_unlock(&pool->lock); > if (list_empty(&zhdr->buddy)) > add_to_unbuddied(pool, zhdr); > - z3fold_page_unlock(zhdr); > clear_bit(PAGE_CLAIMED, &page->private); > + z3fold_page_unlock(zhdr); > } > > /* We started off locked to we need to lock the pool back */ > @@ -1577,8 +1577,8 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa > if (!z3fold_page_trylock(zhdr)) > return -EAGAIN; > if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) { > - z3fold_page_unlock(zhdr); > clear_bit(PAGE_CLAIMED, &page->private); > + z3fold_page_unlock(zhdr); > return -EBUSY; > } > if (work_pending(&zhdr->work)) { Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com> > -- > 2.23.0 >
diff --git a/mm/z3fold.c b/mm/z3fold.c index a1c150fc8def..4a3cd2ff15b0 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -1221,8 +1221,8 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) return; } if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { - put_z3fold_header(zhdr); clear_bit(PAGE_CLAIMED, &page->private); + put_z3fold_header(zhdr); return; } if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { @@ -1424,8 +1424,8 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) spin_unlock(&pool->lock); if (list_empty(&zhdr->buddy)) add_to_unbuddied(pool, zhdr); - z3fold_page_unlock(zhdr); clear_bit(PAGE_CLAIMED, &page->private); + z3fold_page_unlock(zhdr); } /* We started off locked to we need to lock the pool back */ @@ -1577,8 +1577,8 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa if (!z3fold_page_trylock(zhdr)) return -EAGAIN; if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) { - z3fold_page_unlock(zhdr); clear_bit(PAGE_CLAIMED, &page->private); + z3fold_page_unlock(zhdr); return -EBUSY; } if (work_pending(&zhdr->work)) {
Think about the below race window: CPU1 CPU2 z3fold_reclaim_page z3fold_free test_and_set_bit PAGE_CLAIMED failed to reclaim page z3fold_page_lock(zhdr); add back to the lru list; z3fold_page_unlock(zhdr); get_z3fold_header page_claimed=test_and_set_bit PAGE_CLAIMED clear_bit(PAGE_CLAIMED, &page->private); if (!page_claimed) /* it's false true */ free_handle is not called free_handle won't be called in this case. So z3fold_buddy_slots will leak. Fix it by always clear PAGE_CLAIMED under z3fold page lock. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/z3fold.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)