On Fri, 14 Apr 2017, Bart Van Assche wrote:
> 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@xxxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
Changing a fundamental function, silently not to do its essential job,
when something in the kernel has forgotten (or is slow to) unlock_page():
that seems very wrong to me in many ways. But linux-fsdevel, Cc'ed, will
be a better forum to advise on how to solve the problem you're seeing.
Hugh
> ---
> 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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