From patchwork Thu Jun 9 16:09:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 12875782 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12A21C43334 for ; Thu, 9 Jun 2022 16:09:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232457AbiFIQJb (ORCPT ); Thu, 9 Jun 2022 12:09:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236387AbiFIQJa (ORCPT ); Thu, 9 Jun 2022 12:09:30 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3066D31212 for ; Thu, 9 Jun 2022 09:09:26 -0700 (PDT) Date: Thu, 9 Jun 2022 18:09:22 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1654790963; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=9T9BroPC8U1J8ThUR5sFvLY5XwQH7HjX+JJ0jqAEnvA=; b=4k7IZT2g4c6tjuH2C716VAHNpRaFrUaFylgJOAwlG1eqUqoQBHNdI07cGAm9/1/fVdbSHm mzUSv8On3p5Buc9OSd0IiCUlq9QbMf7qokWSSSB33C6AWMLF4nT5Vym5g22Ej3KJGXP8b9 1468FHzeZs/wHM1wnYathd7iKclYV5eB57CP6XtxLBM5HIxJgYOvYnupazXQ3GTkkY01cH FhvFIpq640I1Pu1+EoHKR9I7NaPv+K1PZN4V075tsMVnFPZ0QltMldxrdBgWO9IQuciMDd 4+ahw+4ni4KGd9mWhffuoGIBcWKeuCqG9eA7ROk6ZA/gw/1g/qgSzt3nGf5qlw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1654790963; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=9T9BroPC8U1J8ThUR5sFvLY5XwQH7HjX+JJ0jqAEnvA=; b=arAA6grq7+qH/FFdXmTkADPIS+S120DttN4g/UFvknhi5WlvmoDg7FM0bjQ5NCyvGyjkOh OzCeDlRcPcME61DQ== From: Sebastian Andrzej Siewior To: linux-block@vger.kernel.org Cc: Jens Axboe , Mike Galbraith , Minchan Kim , Nitin Gupta , Sergey Senozhatsky , Thomas Gleixner Subject: zram: Replace bit spinlocks with spinlock_t for PREEMPT_RT. Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Mike Galbraith The bit spinlock disables preemption on PREEMPT_RT. With disabled preemption it is not allowed to acquire other sleeping locks which includes invoking zs_free(). Use a spinlock_t on PREEMPT_RT for locking and set/ clear ZRAM_LOCK after the lock has been acquired/ dropped. Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- I'm simply forwarding Mike's patch here. The other alternative is to let the driver depend on !PREEMPT_RT. I can't tell likely it is that this driver is used. Mike most likely stumbled upon it while running LTP. drivers/block/zram/zram_drv.c | 36 ++++++++++++++++++++++++++++++++++++ drivers/block/zram/zram_drv.h | 3 +++ 2 files changed, 39 insertions(+) --- --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -58,6 +58,40 @@ static void zram_free_page(struct zram * static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, u32 index, int offset, struct bio *bio); +#ifdef CONFIG_PREEMPT_RT +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) +{ + size_t index; + + for (index = 0; index < num_pages; index++) + spin_lock_init(&zram->table[index].lock); +} + +static int zram_slot_trylock(struct zram *zram, u32 index) +{ + int ret; + + ret = spin_trylock(&zram->table[index].lock); + if (ret) + __set_bit(ZRAM_LOCK, &zram->table[index].flags); + return ret; +} + +static void zram_slot_lock(struct zram *zram, u32 index) +{ + spin_lock(&zram->table[index].lock); + __set_bit(ZRAM_LOCK, &zram->table[index].flags); +} + +static void zram_slot_unlock(struct zram *zram, u32 index) +{ + __clear_bit(ZRAM_LOCK, &zram->table[index].flags); + spin_unlock(&zram->table[index].lock); +} + +#else + +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) { } static int zram_slot_trylock(struct zram *zram, u32 index) { @@ -73,6 +107,7 @@ static void zram_slot_unlock(struct zram { bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags); } +#endif static inline bool init_done(struct zram *zram) { @@ -1195,6 +1230,7 @@ static bool zram_meta_alloc(struct zram if (!huge_class_size) huge_class_size = zs_huge_class_size(zram->mem_pool); + zram_meta_init_table_locks(zram, num_pages); return true; } --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -63,6 +63,9 @@ struct zram_table_entry { unsigned long element; }; unsigned long flags; +#ifdef CONFIG_PREEMPT_RT + spinlock_t lock; +#endif #ifdef CONFIG_ZRAM_MEMORY_TRACKING ktime_t ac_time; #endif