From: Vitaly Wool <vitalywool@xxxxxxxxx> Subject: z3fold: fix reclaim lock-ups Do not try to optimize in-page object layout while the page is under reclaim. This fixes lock-ups on reclaim and improves reclaim performance at the same time. [akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] Link: http://lkml.kernel.org/r/20180430125800.444cae9706489f412ad12621@xxxxxxxxx Signed-off-by: Vitaly Wool <vitaly.vul@xxxxxxxx> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx> Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> Cc: <Oleksiy.Avramchenko@xxxxxxxx> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/z3fold.c | 42 ++++++++++++++++++++++++++++++------------ 1 file changed, 30 insertions(+), 12 deletions(-) diff -puN mm/z3fold.c~z3fold-fix-reclaim-lock-ups mm/z3fold.c --- a/mm/z3fold.c~z3fold-fix-reclaim-lock-ups +++ a/mm/z3fold.c @@ -144,7 +144,8 @@ enum z3fold_page_flags { PAGE_HEADLESS = 0, MIDDLE_CHUNK_MAPPED, NEEDS_COMPACTING, - PAGE_STALE + PAGE_STALE, + UNDER_RECLAIM }; /***************** @@ -173,6 +174,7 @@ static struct z3fold_header *init_z3fold clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); clear_bit(NEEDS_COMPACTING, &page->private); clear_bit(PAGE_STALE, &page->private); + clear_bit(UNDER_RECLAIM, &page->private); spin_lock_init(&zhdr->page_lock); kref_init(&zhdr->refcount); @@ -756,6 +758,10 @@ static void z3fold_free(struct z3fold_po atomic64_dec(&pool->pages_nr); return; } + if (test_bit(UNDER_RECLAIM, &page->private)) { + z3fold_page_unlock(zhdr); + return; + } if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { z3fold_page_unlock(zhdr); return; @@ -840,6 +846,8 @@ static int z3fold_reclaim_page(struct z3 kref_get(&zhdr->refcount); list_del_init(&zhdr->buddy); zhdr->cpu = -1; + set_bit(UNDER_RECLAIM, &page->private); + break; } list_del_init(&page->lru); @@ -887,25 +895,35 @@ static int z3fold_reclaim_page(struct z3 goto next; } next: - spin_lock(&pool->lock); if (test_bit(PAGE_HEADLESS, &page->private)) { if (ret == 0) { - spin_unlock(&pool->lock); free_z3fold_page(page); return 0; } - } else if (kref_put(&zhdr->refcount, release_z3fold_page)) { - atomic64_dec(&pool->pages_nr); + spin_lock(&pool->lock); + list_add(&page->lru, &pool->lru); + spin_unlock(&pool->lock); + } else { + z3fold_page_lock(zhdr); + clear_bit(UNDER_RECLAIM, &page->private); + if (kref_put(&zhdr->refcount, + release_z3fold_page_locked)) { + atomic64_dec(&pool->pages_nr); + return 0; + } + /* + * if we are here, the page is still not completely + * free. Take the global pool lock then to be able + * to add it back to the lru list + */ + spin_lock(&pool->lock); + list_add(&page->lru, &pool->lru); spin_unlock(&pool->lock); - return 0; + z3fold_page_unlock(zhdr); } - /* - * Add to the beginning of LRU. - * Pool lock has to be kept here to ensure the page has - * not already been released - */ - list_add(&page->lru, &pool->lru); + /* We started off locked to we need to lock the pool back */ + spin_lock(&pool->lock); } spin_unlock(&pool->lock); return -EAGAIN; _
