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From: Bart Van Assche <bart.vanassche@sandisk.com>
Subject: [PATCH] mm: Make truncate_inode_pages_range() killable
Date: Fri, 14 Apr 2017 14:55:07 -0700
Message-ID: <20170414215507.27682-1-bart.vanassche@sandisk.com>
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Sender: owner-linux-mm@kvack.org
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To: Andrew Morton <akpm@linux-foundation.org>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>, Oleg Nesterov <oleg@redhat.com>, Michal Hocko <mhocko@suse.com>, Mel Gorman <mgorman@techsingularity.net>, Hugh Dickins <hughd@google.com>, Mike Snitzer <snitzer@redhat.com>, Jan Kara <jack@suse.cz>, Hannes Reinecke <hare@suse.com>, linux-mm@kvack.org

The default behavior of multipathd is to run kpartx against newly
discovered paths. Avoid that these kpartx processes become unkillable
if there are no paths left and when using queue_if_no_path. This patch
avoids that kpartx sporadically hangs as follows:

Call Trace:
 __schedule+0x3df/0xc10
 schedule+0x3d/0x90
 io_schedule+0x16/0x40
 __lock_page+0x111/0x140
 truncate_inode_pages_range+0x462/0x790
 truncate_inode_pages+0x15/0x20
 kill_bdev+0x35/0x40
 __blkdev_put+0x76/0x220
 blkdev_put+0x4e/0x170
 blkdev_close+0x25/0x30
 __fput+0xed/0x1f0
 ____fput+0xe/0x10
 task_work_run+0x85/0xc0
 do_exit+0x311/0xc70
 do_group_exit+0x50/0xd0
 get_signal+0x2c7/0x930
 do_signal+0x28/0x6b0
 exit_to_usermode_loop+0x62/0xa0
 do_syscall_64+0xda/0x140
 entry_SYSCALL64_slow_path+0x25/0x25

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Hannes Reinecke <hare@suse.com>
Cc: linux-mm@kvack.org
---
 mm/truncate.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 6263affdef88..91abd16d74f8 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -20,6 +20,7 @@
 #include <linux/task_io_accounting_ops.h>
 #include <linux/buffer_head.h>	/* grr. try_to_release_page,
 				   do_invalidatepage */
+#include <linux/sched/signal.h>
 #include <linux/shmem_fs.h>
 #include <linux/cleancache.h>
 #include <linux/rmap.h>
@@ -366,7 +367,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 		return;
 
 	index = start;
-	for ( ; ; ) {
+	for ( ; !signal_pending_state(TASK_WAKEKILL, current); ) {
 		cond_resched();
 		if (!pagevec_lookup_entries(&pvec, mapping, index,
 			min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) {
@@ -400,7 +401,8 @@ void truncate_inode_pages_range(struct address_space *mapping,
 				continue;
 			}
 
-			lock_page(page);
+			if (lock_page_killable(page))
+				break;
 			WARN_ON(page_to_index(page) != index);
 			wait_on_page_writeback(page);
 			truncate_inode_page(mapping, page);
-- 
2.12.2

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