[PATCH] mm: Make truncate_inode_pages_range() killable

[Bart Van Assche <bart.vanassche@sandisk.com>]

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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