From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750703AbWGTRDP (ORCPT ); Thu, 20 Jul 2006 13:03:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750724AbWGTRDP (ORCPT ); Thu, 20 Jul 2006 13:03:15 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:14293 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1750703AbWGTRDO (ORCPT ); Thu, 20 Jul 2006 13:03:14 -0400 Date: Thu, 20 Jul 2006 12:00:54 -0500 From: "Serge E. Hallyn" To: Andrew Morton Cc: "Serge E. Hallyn" , hugh@veritas.com, torvalds@osdl.org, linux-kernel@vger.kernel.org Subject: Re: please revert kthread from loop.c Message-ID: <20060720170054.GB27601@sergelap.austin.ibm.com> References: <20060627054612.GA15657@sergelap.austin.ibm.com> <20060711194932.GA27176@sergelap.austin.ibm.com> <20060711171752.4993903a.akpm@osdl.org> <20060712032647.GA24595@sergelap.austin.ibm.com> <20060711204637.bba6e966.akpm@osdl.org> <20060712230228.GA19656@sergelap.austin.ibm.com> <20060713023829.c19881be.akpm@osdl.org> <20060713133602.GH14665@sergelap.austin.ibm.com> <20060713075749.982b3478.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060713075749.982b3478.akpm@osdl.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Quoting Andrew Morton (akpm@osdl.org): > On Thu, 13 Jul 2006 08:36:02 -0500 > "Serge E. Hallyn" wrote: > > > Quoting Andrew Morton (akpm@osdl.org): > > > > > Again: why is this so hard? It shouldn't be. Perhaps because loop is > > > using completions in bizarre ways where it should be using > > > wake_up_process(), wait_event(), etc. > > > > Ah. > > > > wait_event() actually seems like the way to go - I'll try to follow the > > example in fs/ocfs2/journal.c. > > I suspect quite a lot of changes to loop.c would fall out. For a start, in > a sufficiently-simplified implementation lo_pending would perhaps go away - > just test the NULLness of the top of the list of BIOs. True - here is an attempt at that: Subject: [PATCH] kthread: convert loop.c to kthread From: Serge E. Hallyn Date: 1153345222 -0500 Convert loop.c from the deprecated kernel_thread to kthread. This patch simplifies the code quite a bit and passes similar testing to the previous submission on both emulated x86 and s390. Changes since last submission: switched to using a rather simple loop based on wait_event_interruptible. Signed-off-by: Serge E. Hallyn --- drivers/block/loop.c | 69 +++++++++++++++++--------------------------------- include/linux/loop.h | 5 +--- 2 files changed, 26 insertions(+), 48 deletions(-) c5f5e9d7016d6fb2b43aa4b13aea302ac367a28c diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 7b3b94d..0468785 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -72,6 +72,7 @@ #include #include #include +#include #include @@ -522,15 +523,12 @@ static int loop_make_request(request_que goto out; if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY))) goto out; - lo->lo_pending++; loop_add_bio(lo, old_bio); + wake_up(&lo->lo_event); spin_unlock_irq(&lo->lo_lock); - complete(&lo->lo_bh_done); return 0; out: - if (lo->lo_pending == 0) - complete(&lo->lo_bh_done); spin_unlock_irq(&lo->lo_lock); bio_io_error(old_bio, old_bio->bi_size); return 0; @@ -570,14 +568,18 @@ static inline void loop_handle_bio(struc * to avoid blocking in our make_request_fn. it also does loop decrypting * on reads for block backed loop, as that is too heavy to do from * b_end_io context where irqs may be disabled. + * + * Loop explanation: loop_clr_fd() sets lo_state to Lo_rundown before + * calling kthread_stop(). Therefore once kthread_should_stop() is + * true, make_request will not place any more requests. Therefore + * once kthread_should_stop() is true and lo_bio is NULL, we are + * done with the loop. */ static int loop_thread(void *data) { struct loop_device *lo = data; struct bio *bio; - daemonize("loop%d", lo->lo_number); - /* * loop can be used in an encrypted device, * hence, it mustn't be stopped at all @@ -587,47 +589,21 @@ static int loop_thread(void *data) set_user_nice(current, -20); - lo->lo_state = Lo_bound; - lo->lo_pending = 1; - - /* - * complete it, we are running - */ - complete(&lo->lo_done); + while (!kthread_should_stop() || lo->lo_bio) { - for (;;) { - int pending; + wait_event_interruptible(lo->lo_event, + lo->lo_bio || kthread_should_stop()); - if (wait_for_completion_interruptible(&lo->lo_bh_done)) + if (!lo->lo_bio) continue; - spin_lock_irq(&lo->lo_lock); - - /* - * could be completed because of tear-down, not pending work - */ - if (unlikely(!lo->lo_pending)) { - spin_unlock_irq(&lo->lo_lock); - break; - } - bio = loop_get_bio(lo); - lo->lo_pending--; - pending = lo->lo_pending; spin_unlock_irq(&lo->lo_lock); BUG_ON(!bio); loop_handle_bio(lo, bio); - - /* - * upped both for pending work and tear-down, lo_pending - * will hit zero then - */ - if (unlikely(!pending)) - break; } - complete(&lo->lo_done); return 0; } @@ -837,10 +813,15 @@ static int loop_set_fd(struct loop_devic set_blocksize(bdev, lo_blocksize); - error = kernel_thread(loop_thread, lo, CLONE_KERNEL); - if (error < 0) + lo->lo_thread = kthread_create(loop_thread, lo, "loop%d", + lo->lo_number); + if (IS_ERR(lo->lo_thread)) { + error = PTR_ERR(lo->lo_thread); + lo->lo_thread = NULL; goto out_putf; - wait_for_completion(&lo->lo_done); + } + lo->lo_state = Lo_bound; + wake_up_process(lo->lo_thread); return 0; out_putf: @@ -904,12 +885,9 @@ static int loop_clr_fd(struct loop_devic spin_lock_irq(&lo->lo_lock); lo->lo_state = Lo_rundown; - lo->lo_pending--; - if (!lo->lo_pending) - complete(&lo->lo_bh_done); spin_unlock_irq(&lo->lo_lock); - wait_for_completion(&lo->lo_done); + kthread_stop(lo->lo_thread); lo->lo_backing_file = NULL; @@ -922,6 +900,7 @@ static int loop_clr_fd(struct loop_devic lo->lo_sizelimit = 0; lo->lo_encrypt_key_size = 0; lo->lo_flags = 0; + lo->lo_thread = NULL; memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE); memset(lo->lo_crypt_name, 0, LO_NAME_SIZE); memset(lo->lo_file_name, 0, LO_NAME_SIZE); @@ -1284,9 +1263,9 @@ static int __init loop_init(void) if (!lo->lo_queue) goto out_mem4; mutex_init(&lo->lo_ctl_mutex); - init_completion(&lo->lo_done); - init_completion(&lo->lo_bh_done); lo->lo_number = i; + lo->lo_thread = NULL; + init_waitqueue_head(&lo->lo_event); spin_lock_init(&lo->lo_lock); disk->major = LOOP_MAJOR; disk->first_minor = i; diff --git a/include/linux/loop.h b/include/linux/loop.h index e76c761..191a595 100644 --- a/include/linux/loop.h +++ b/include/linux/loop.h @@ -59,10 +59,9 @@ struct loop_device { struct bio *lo_bio; struct bio *lo_biotail; int lo_state; - struct completion lo_done; - struct completion lo_bh_done; struct mutex lo_ctl_mutex; - int lo_pending; + struct task_struct *lo_thread; + wait_queue_head_t lo_event; request_queue_t *lo_queue; }; -- 1.1.6