From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3AD3C19759 for ; Thu, 1 Aug 2019 09:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD49D20644 for ; Thu, 1 Aug 2019 09:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730806AbfHAJCR (ORCPT ); Thu, 1 Aug 2019 05:02:17 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:3690 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730567AbfHAJCR (ORCPT ); Thu, 1 Aug 2019 05:02:17 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id EC4231E189F8CB4F00ED; Thu, 1 Aug 2019 17:02:10 +0800 (CST) Received: from huawei.com (10.90.53.225) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.439.0; Thu, 1 Aug 2019 17:01:56 +0800 From: Zhihao Cheng To: , CC: , , Subject: [RFC] ubi: ubi_wl_get_peb: Replace a limited number of attempts with polling while getting PEB Date: Thu, 1 Aug 2019 17:07:49 +0800 Message-ID: <1564650469-130037-1-git-send-email-chengzhihao1@huawei.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.90.53.225] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Running pressure test io_paral (A pressure ubi test in mtd-utils) on an UBI device with fewer PEBs (fastmap enabled) may cause ENOSPC errors and make UBI device read-only, but there are still free PEBs on the UBI device. This problem can be easily reproduced by performing the following steps on a 2-core machine: $ modprobe nandsim first_id_byte=0x20 second_id_byte=0x33 parts=80 $ modprobe ubi mtd="0,0" fm_autoconvert $ ./io_paral /dev/ubi0 We may see the following verbose: (output) [io_paral] update_volume():105: function write() failed with error 30 (Read-only file system) [io_paral] update_volume():108: failed to write 380 bytes at offset 95920 of volume 2 [io_paral] update_volume():109: update: 97088 bytes [io_paral] write_thread():227: function pwrite() failed with error 28 (No space left on device) [io_paral] write_thread():229: cannot write 15872 bytes to offs 31744, wrote -1 (dmesg) ubi0 error: ubi_wl_get_peb [ubi]: Unable to get a free PEB from user WL pool ubi0 warning: ubi_eba_write_leb [ubi]: switch to read-only mode ubi0 error: ubi_io_write [ubi]: read-only mode CPU: 0 PID: 2027 Comm: io_paral Not tainted 5.3.0-rc2-00001-g5986cd0 #9 ubi0 warning: try_write_vid_and_data [ubi]: failed to write VID header to LEB 2:5, PEB 18 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0 -0-ga698c8995f-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x85/0xba ubi_eba_write_leb+0xa1e/0xa40 [ubi] vol_cdev_write+0x307/0x520 [ubi] ubi0 error: vol_cdev_write [ubi]: cannot accept more 380 bytes of data, error -30 vfs_write+0xfa/0x280 ksys_pwrite64+0xc5/0xe0 __x64_sys_pwrite64+0x22/0x30 do_syscall_64+0xbf/0x440 In function ubi_wl_get_peb, the operation of filling the pool (ubi_update_fastmap) with free PEBs and fetching a free PEB from the pool is not atomic. After thread A filling the pool with free PEB, free PEB may be taken away by thread B. When thread A checks the expression again, the condition is still unsatisfactory. At this time, there may still be free PEBs on UBI that can be filled into the pool. So, ubi_wl_get_peb (in fastmap-wil.c) should be implemented to obtain a free PEB by polling method. The polling exit condition is that there is no free PEBs on UBI, no free PEBs in pool, and ubi->works_count is 0. Signed-off-by: Zhihao Cheng --- drivers/mtd/ubi/fastmap-wl.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c index d9e2e3a..c5512cf 100644 --- a/drivers/mtd/ubi/fastmap-wl.c +++ b/drivers/mtd/ubi/fastmap-wl.c @@ -196,7 +196,7 @@ static int produce_free_peb(struct ubi_device *ubi) */ int ubi_wl_get_peb(struct ubi_device *ubi) { - int ret, retried = 0; + int ret; struct ubi_fm_pool *pool = &ubi->fm_pool; struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool; @@ -220,13 +220,14 @@ int ubi_wl_get_peb(struct ubi_device *ubi) } if (pool->used == pool->size) { - spin_unlock(&ubi->wl_lock); - if (retried) { + if (!ubi->free.rb_node && ubi->works_count == 0) { ubi_err(ubi, "Unable to get a free PEB from user WL pool"); + ubi_assert(list_empty(&ubi->works)); + spin_unlock(&ubi->wl_lock); ret = -ENOSPC; goto out; } - retried = 1; + spin_unlock(&ubi->wl_lock); up_read(&ubi->fm_eba_sem); ret = produce_free_peb(ubi); if (ret < 0) { -- 2.7.4