From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guoqing Jiang Subject: [PATCH 1/3] raid5: call clear_batch_ready before set STRIPE_ACTIVE Date: Tue, 16 Jun 2020 11:25:50 +0200 Message-ID: <20200616092552.1754-1-guoqing.jiang@cloud.ionos.com> Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org Cc: song@kernel.org, Guoqing Jiang List-Id: linux-raid.ids We tried to only put the head sh of batch list to handle_list, then the handle_stripe doesn't handle other members in the batch list. However, we still got the calltrace in break_stripe_batch_list. [593764.644269] stripe state: 2003 kernel: [593764.644299] ------------[ cut here ]------------ kernel: [593764.644308] WARNING: CPU: 12 PID: 856 at drivers/md/raid5.c:4625 break_stripe_batch_list+0x203/0x240 [raid456] [...] kernel: [593764.644363] Call Trace: kernel: [593764.644370] handle_stripe+0x907/0x20c0 [raid456] kernel: [593764.644376] ? __wake_up_common_lock+0x89/0xc0 kernel: [593764.644379] handle_active_stripes.isra.57+0x35f/0x570 [raid456] kernel: [593764.644382] ? raid5_wakeup_stripe_thread+0x96/0x1f0 [raid456] kernel: [593764.644385] raid5d+0x480/0x6a0 [raid456] kernel: [593764.644390] ? md_thread+0x11f/0x160 kernel: [593764.644392] md_thread+0x11f/0x160 kernel: [593764.644394] ? wait_woken+0x80/0x80 kernel: [593764.644396] kthread+0xfc/0x130 kernel: [593764.644398] ? find_pers+0x70/0x70 kernel: [593764.644399] ? kthread_create_on_node+0x70/0x70 kernel: [593764.644401] ret_from_fork+0x1f/0x30 As we can see, the stripe was set with STRIPE_ACTIVE and STRIPE_HANDLE, and only handle_stripe could set those flags then return. And since the stipe was already in the batch list, we need to return earlier before set the two flags. And after dig a little about git history especially commit 3664847d95e6 ("md/raid5: fix a race condition in stripe batch"), it seems the batched stipe still could be handled by handle_stipe, then handle_stipe needs to return earlier if clear_batch_ready to return true. Signed-off-by: Guoqing Jiang --- Another alternative would be just not warn if STRIPE_ACTIVE is valid for the batched list. What do you think? Thanks, Guoqing drivers/md/raid5.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index ab8067f9ce8c..a35332364f07 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4682,6 +4682,16 @@ static void handle_stripe(struct stripe_head *sh) struct r5dev *pdev, *qdev; clear_bit(STRIPE_HANDLE, &sh->state); + + /* + * handle_stripe should not continue handle the batched stripe, only + * the head of batch list or lone stripe can continue. Otherwise we + * could see break_stripe_batch_list warns about the STRIPE_ACTIVE + * is set for the batched stripe. + */ + if (clear_batch_ready(sh)) + return; + if (test_and_set_bit_lock(STRIPE_ACTIVE, &sh->state)) { /* already being handled, ensure it gets handled * again when current action finishes */ @@ -4689,11 +4699,6 @@ static void handle_stripe(struct stripe_head *sh) return; } - if (clear_batch_ready(sh) ) { - clear_bit_unlock(STRIPE_ACTIVE, &sh->state); - return; - } - if (test_and_clear_bit(STRIPE_BATCH_ERR, &sh->state)) break_stripe_batch_list(sh, 0); -- 2.17.1