From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail177-1.suw61.mandrillapp.com ([198.2.177.1]:56022 "EHLO mail177-1.suw61.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755684AbcCAXzq (ORCPT ); Tue, 1 Mar 2016 18:55:46 -0500 Received: from pmta06.mandrill.prod.suw01.rsglab.com (127.0.0.1) by mail177-1.suw61.mandrillapp.com id hqom0422rtkj for ; Tue, 1 Mar 2016 23:54:25 +0000 (envelope-from ) From: Greg Kroah-Hartman Subject: [PATCH 4.4 123/342] dm snapshot: fix hung bios when copy error occurs To: Cc: Greg Kroah-Hartman , , Mikulas Patocka , Mike Snitzer Message-Id: <20160301234531.929572767@linuxfoundation.org> In-Reply-To: <20160301234527.990448862@linuxfoundation.org> References: <20160301234527.990448862@linuxfoundation.org> Date: Tue, 01 Mar 2016 23:54:25 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka commit 385277bfb57faac44e92497104ba542cdd82d5fe upstream. When there is an error copying a chunk dm-snapshot can incorrectly hold associated bios indefinitely, resulting in hung IO. The function copy_callback sets pe->error if there was error copying the chunk, and then calls complete_exception. complete_exception calls pending_complete on error, otherwise it calls commit_exception with commit_callback (and commit_callback calls complete_exception). The persistent exception store (dm-snap-persistent.c) assumes that calls to prepare_exception and commit_exception are paired. persistent_prepare_exception increases ps->pending_count and persistent_commit_exception decreases it. If there is a copy error, persistent_prepare_exception is called but persistent_commit_exception is not. This results in the variable ps->pending_count never returning to zero and that causes some pending exceptions (and their associated bios) to be held forever. Fix this by unconditionally calling commit_exception regardless of whether the copy was successful. A new "valid" parameter is added to commit_exception -- when the copy fails this parameter is set to zero so that the chunk that failed to copy (and all following chunks) is not recorded in the snapshot store. Also, remove commit_callback now that it is merely a wrapper around pending_complete. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-exception-store.h | 2 +- drivers/md/dm-snap-persistent.c | 5 ++++- drivers/md/dm-snap-transient.c | 4 ++-- drivers/md/dm-snap.c | 20 +++++--------------- 4 files changed, 12 insertions(+), 19 deletions(-) --- a/drivers/md/dm-exception-store.h +++ b/drivers/md/dm-exception-store.h @@ -69,7 +69,7 @@ struct dm_exception_store_type { * Update the metadata with this exception. */ void (*commit_exception) (struct dm_exception_store *store, - struct dm_exception *e, + struct dm_exception *e, int valid, void (*callback) (void *, int success), void *callback_context); --- a/drivers/md/dm-snap-persistent.c +++ b/drivers/md/dm-snap-persistent.c @@ -695,7 +695,7 @@ static int persistent_prepare_exception( } static void persistent_commit_exception(struct dm_exception_store *store, - struct dm_exception *e, + struct dm_exception *e, int valid, void (*callback) (void *, int success), void *callback_context) { @@ -704,6 +704,9 @@ static void persistent_commit_exception( struct core_exception ce; struct commit_callback *cb; + if (!valid) + ps->valid = 0; + ce.old_chunk = e->old_chunk; ce.new_chunk = e->new_chunk; write_exception(ps, ps->current_committed++, &ce); --- a/drivers/md/dm-snap-transient.c +++ b/drivers/md/dm-snap-transient.c @@ -52,12 +52,12 @@ static int transient_prepare_exception(s } static void transient_commit_exception(struct dm_exception_store *store, - struct dm_exception *e, + struct dm_exception *e, int valid, void (*callback) (void *, int success), void *callback_context) { /* Just succeed */ - callback(callback_context, 1); + callback(callback_context, valid); } static void transient_usage(struct dm_exception_store *store, --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1438,8 +1438,9 @@ static void __invalidate_snapshot(struct dm_table_event(s->ti->table); } -static void pending_complete(struct dm_snap_pending_exception *pe, int success) +static void pending_complete(void *context, int success) { + struct dm_snap_pending_exception *pe = context; struct dm_exception *e; struct dm_snapshot *s = pe->snap; struct bio *origin_bios = NULL; @@ -1509,24 +1510,13 @@ out: free_pending_exception(pe); } -static void commit_callback(void *context, int success) -{ - struct dm_snap_pending_exception *pe = context; - - pending_complete(pe, success); -} - static void complete_exception(struct dm_snap_pending_exception *pe) { struct dm_snapshot *s = pe->snap; - if (unlikely(pe->copy_error)) - pending_complete(pe, 0); - - else - /* Update the metadata if we are persistent */ - s->store->type->commit_exception(s->store, &pe->e, - commit_callback, pe); + /* Update the metadata if we are persistent */ + s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error, + pending_complete, pe); } /*