From patchwork Tue Jun 26 17:09:27 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Christie X-Patchwork-Id: 10489729 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 93DE46023A for ; Tue, 26 Jun 2018 17:09:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 72FE9286B1 for ; Tue, 26 Jun 2018 17:09:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 66104286C0; Tue, 26 Jun 2018 17:09:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,T_TVD_MIME_EPI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 98122286B1 for ; Tue, 26 Jun 2018 17:09:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932799AbeFZRJb (ORCPT ); Tue, 26 Jun 2018 13:09:31 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36010 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932636AbeFZRJ2 (ORCPT ); Tue, 26 Jun 2018 13:09:28 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 08CD6401EF16; Tue, 26 Jun 2018 17:09:28 +0000 (UTC) Received: from [10.10.126.23] (ovpn-126-23.rdu2.redhat.com [10.10.126.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 58D262314B; Tue, 26 Jun 2018 17:09:27 +0000 (UTC) Subject: Re: [PATCH 00/20] SCSI target patches for kernel v4.19 To: Bart Van Assche , "Martin K . Petersen" References: <20180622215307.8758-1-bart.vanassche@wdc.com> Cc: Christoph Hellwig , target-devel@vger.kernel.org From: Mike Christie Message-ID: <5B327347.8040904@redhat.com> Date: Tue, 26 Jun 2018 12:09:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20180622215307.8758-1-bart.vanassche@wdc.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 26 Jun 2018 17:09:28 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 26 Jun 2018 17:09:28 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mchristi@redhat.com' RCPT:'' Sender: target-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: target-devel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On 06/22/2018 04:52 PM, Bart Van Assche wrote: > Hello, > > This is a series with bug fixes and code simplifications mainly for the SCSI > target core. The following tests have been run against this patch series for > both the iSCSI and SRPT target drivers: > - Run the libiscsi conformance tests. > - For the SRP target driver, run the srp-test software. > > Please consider this patch series for kernel v4.19. > > Thanks, > > Bart. > > Bart Van Assche (20): > target: Use config_item_name() instead of open-coding it > target: Avoid that EXTENDED COPY commands trigger lock inversion > target: Move a list_del_init() statement > target: Rename transport_init_session() into transport_alloc_session() > target: Introduce transport_init_session() > target: Make the session shutdown code also wait for commands that are > being aborted > target: Document when CMD_T_STOP and CMD_T_COMPLETE are set > target: Simplify core_tmr_handle_tas_abort() > target: Fold core_tmr_handle_tas_abort() into > transport_cmd_finish_abort() > target: Simplify transport_generic_free_cmd() (1/2) > target: Simplify transport_generic_free_cmd() (2/2) > target: Simplify the code for waiting for command completion > target/iscsi: Reduce number of __iscsit_free_cmd() callers > target/iscsi: Make iscsit_ta_authentication() respect the output > buffer size > target: Remove second argument from fabric_make_tpg() > target/tcm_loop: Avoid that static checkers warn about dead code > target: Do not duplicate the code that marks that a command has sense > data > target: Send unit attention condition even if the sense buffer is too > small > target: Fix handling of removed LUNs > target: Remove se_dev_entry.ua_count > Looks ok to me. Reviewed-by: Mike Christie Martin, there was going to be one conflict between my patches and Bart's set. I was not sure how you wanted to handle it because I was not sure which would be merged first. The problem was that Bart's patch in this set: [PATCH 02/20] target: Avoid that EXTENDED COPY commands trigger lock inversion modified target_find_device and I was removing the last user of it in my set you just merged. I attached a updated version of Bart's: [PATCH 02/20] target: Avoid that EXTENDED COPY commands trigger lock inversion that just removes target_find_device instead of fixing it up, so Bart does not have to resend/rework any of his patches. From 13173cb9edcad9d5030de01eb097f8c9d88fb5d8 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 26 Jun 2018 12:01:19 -0500 Subject: [PATCH] target: Avoid that EXTENDED COPY commands trigger lock inversion The approach for adding a device to the devices_idr data structure and for removing it is as follows: * &dev->dev_group.cg_item is initialized before a device is added to devices_idr. * If the reference count of a device drops to zero then target_free_device() removes the device from devices_idr. * All devices_idr manipulations are protected by device_mutex. This means that increasing the reference count of a device is sufficient to prevent removal from devices_idr and also that it is safe access dev_group.cg_item for any device that is referenced by devices_idr. Use this to modify target_find_device() and target_for_each_device() such that these functions no longer introduce a dependency between device_mutex and the configfs root inode mutex. Note: it is safe to pass a NULL pointer to config_item_put() and also to config_item_get_unless_zero(). This patch prevents that lockdep reports the following complaint: ====================================================== WARNING: possible circular locking dependency detected 4.12.0-rc1-dbg+ #1 Not tainted ------------------------------------------------------ rmdir/12053 is trying to acquire lock: (device_mutex#2){+.+.+.}, at: [] target_free_device+0xae/0xf0 [target_core_mod] but task is already holding lock: (&sb->s_type->i_mutex_key#14){++++++}, at: [] vfs_rmdir+0x50/0x140 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&sb->s_type->i_mutex_key#14){++++++}: lock_acquire+0x59/0x80 down_write+0x36/0x70 configfs_depend_item+0x3a/0xb0 [configfs] target_depend_item+0x13/0x20 [target_core_mod] target_xcopy_locate_se_dev_e4_iter+0x87/0x100 [target_core_mod] target_devices_idr_iter+0x16/0x20 [target_core_mod] idr_for_each+0x39/0xc0 target_for_each_device+0x36/0x50 [target_core_mod] target_xcopy_locate_se_dev_e4+0x28/0x80 [target_core_mod] target_xcopy_do_work+0x2e9/0xdd0 [target_core_mod] process_one_work+0x1ca/0x3f0 worker_thread+0x49/0x3b0 kthread+0x109/0x140 ret_from_fork+0x31/0x40 -> #0 (device_mutex#2){+.+.+.}: __lock_acquire+0x101f/0x11d0 lock_acquire+0x59/0x80 __mutex_lock+0x7e/0x950 mutex_lock_nested+0x16/0x20 target_free_device+0xae/0xf0 [target_core_mod] target_core_dev_release+0x10/0x20 [target_core_mod] config_item_put+0x6e/0xb0 [configfs] configfs_rmdir+0x1a6/0x300 [configfs] vfs_rmdir+0xb7/0x140 do_rmdir+0x1f4/0x200 SyS_rmdir+0x11/0x20 entry_SYSCALL_64_fastpath+0x23/0xc2 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sb->s_type->i_mutex_key#14); lock(device_mutex#2); lock(&sb->s_type->i_mutex_key#14); lock(device_mutex#2); *** DEADLOCK *** 3 locks held by rmdir/12053: #0: (sb_writers#10){.+.+.+}, at: [] mnt_want_write+0x1f/0x50 #1: (&sb->s_type->i_mutex_key#14/1){+.+.+.}, at: [] do_rmdir+0x15e/0x200 #2: (&sb->s_type->i_mutex_key#14){++++++}, at: [] vfs_rmdir+0x50/0x140 stack backtrace: CPU: 3 PID: 12053 Comm: rmdir Not tainted 4.12.0-rc1-dbg+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 Call Trace: dump_stack+0x86/0xcf print_circular_bug+0x1c7/0x220 __lock_acquire+0x101f/0x11d0 lock_acquire+0x59/0x80 __mutex_lock+0x7e/0x950 mutex_lock_nested+0x16/0x20 target_free_device+0xae/0xf0 [target_core_mod] target_core_dev_release+0x10/0x20 [target_core_mod] config_item_put+0x6e/0xb0 [configfs] configfs_rmdir+0x1a6/0x300 [configfs] vfs_rmdir+0xb7/0x140 do_rmdir+0x1f4/0x200 SyS_rmdir+0x11/0x20 entry_SYSCALL_64_fastpath+0x23/0xc2 Signed-off-by: Bart Van Assche [drop target_find_device because it is no longer used] Signed-off-by: Mike Christie --- drivers/target/target_core_device.c | 46 +++++++++++++----------------------- include/target/target_core_backend.h | 2 -- 2 files changed, 17 insertions(+), 31 deletions(-) diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c index e27db4d..68cc48b 100644 --- a/drivers/target/target_core_device.c +++ b/drivers/target/target_core_device.c @@ -879,39 +879,21 @@ sector_t target_to_linux_sector(struct se_device *dev, sector_t lb) } EXPORT_SYMBOL(target_to_linux_sector); -/** - * target_find_device - find a se_device by its dev_index - * @id: dev_index - * @do_depend: true if caller needs target_depend_item to be done - * - * If do_depend is true, the caller must do a target_undepend_item - * when finished using the device. - * - * If do_depend is false, the caller must be called in a configfs - * callback or during removal. - */ -struct se_device *target_find_device(int id, bool do_depend) -{ - struct se_device *dev; - - mutex_lock(&device_mutex); - dev = idr_find(&devices_idr, id); - if (dev && do_depend && target_depend_item(&dev->dev_group.cg_item)) - dev = NULL; - mutex_unlock(&device_mutex); - return dev; -} -EXPORT_SYMBOL(target_find_device); - struct devices_idr_iter { + struct config_item *prev_item; int (*fn)(struct se_device *dev, void *data); void *data; }; static int target_devices_idr_iter(int id, void *p, void *data) + __must_hold(&device_mutex) { struct devices_idr_iter *iter = data; struct se_device *dev = p; + int ret; + + config_item_put(iter->prev_item); + iter->prev_item = NULL; /* * We add the device early to the idr, so it can be used @@ -922,7 +904,15 @@ static int target_devices_idr_iter(int id, void *p, void *data) if (!(dev->dev_flags & DF_CONFIGURED)) return 0; - return iter->fn(dev, iter->data); + iter->prev_item = config_item_get_unless_zero(&dev->dev_group.cg_item); + if (!iter->prev_item) + return 0; + mutex_unlock(&device_mutex); + + ret = iter->fn(dev, iter->data); + + mutex_lock(&device_mutex); + return ret; } /** @@ -936,15 +926,13 @@ static int target_devices_idr_iter(int id, void *p, void *data) int target_for_each_device(int (*fn)(struct se_device *dev, void *data), void *data) { - struct devices_idr_iter iter; + struct devices_idr_iter iter = { .fn = fn, .data = data }; int ret; - iter.fn = fn; - iter.data = data; - mutex_lock(&device_mutex); ret = idr_for_each(&devices_idr, target_devices_idr_iter, &iter); mutex_unlock(&device_mutex); + config_item_put(iter.prev_item); return ret; } diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h index 34a15d5..c3ac472 100644 --- a/include/target/target_core_backend.h +++ b/include/target/target_core_backend.h @@ -106,8 +106,6 @@ bool target_lun_is_rdonly(struct se_cmd *); sense_reason_t passthrough_parse_cdb(struct se_cmd *cmd, sense_reason_t (*exec_cmd)(struct se_cmd *cmd)); -struct se_device *target_find_device(int id, bool do_depend); - bool target_sense_desc_format(struct se_device *dev); sector_t target_to_linux_sector(struct se_device *dev, sector_t lb); bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib, -- 2.7.2