Hold multipath.lock around all code that iterates over the
priority_groups list. This patch fixes the following crash:
general protection fault: 0000 [#1] PREEMPT SMP
RIP: 0010:multipath_busy+0x77/0xd0 [dm_multipath]
Call Trace:
dm_mq_queue_rq+0x44/0x110 [dm_mod]
blk_mq_dispatch_rq_list+0x73/0x440
blk_mq_do_dispatch_sched+0x60/0xe0
blk_mq_sched_dispatch_requests+0x11a/0x1a0
__blk_mq_run_hw_queue+0x11f/0x1c0
__blk_mq_delay_run_hw_queue+0x95/0xe0
blk_mq_run_hw_queue+0x25/0x80
blk_mq_flush_plug_list+0x197/0x420
blk_flush_plug_list+0xe4/0x270
blk_finish_plug+0x27/0x40
__do_page_cache_readahead+0x2b4/0x370
force_page_cache_readahead+0xb4/0x110
generic_file_read_iter+0x755/0x970
__vfs_read+0xd2/0x140
vfs_read+0x9b/0x140
SyS_read+0x45/0xa0
do_syscall_64+0x56/0x1a0
entry_SYSCALL64_slow_path+0x25/0x25
>From the disassembly of multipath_busy (0x77 = 119):
./include/linux/blkdev.h:
992 return bdev->bd_disk->queue; /* this is never NULL */
0x00000000000006b4 <+116>: mov (%rax),%rax
0x00000000000006b7 <+119>: mov 0xe0(%rax),%rax
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/md/dm-mpath.c | 40 ++++++++++++++++++++++++++++------------
1 file changed, 28 insertions(+), 12 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index c8faa2b85842..61def92f306a 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -237,10 +237,19 @@ static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
static void free_multipath(struct multipath *m)
{
- struct priority_group *pg, *tmp;
+ struct priority_group *pg;
+ unsigned long flags;
+
+ while (true) {
+ spin_lock_irqsave(&m->lock, flags);
+ pg = list_first_entry_or_null(&m->priority_groups, typeof(*pg),
+ list);
+ if (pg)
+ list_del(&pg->list);
+ spin_unlock_irqrestore(&m->lock, flags);
- list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
- list_del(&pg->list);
+ if (!pg)
+ break;
free_priority_group(pg, m->ti);
}
@@ -337,6 +346,7 @@ static int pg_init_all_paths(struct multipath *m)
}
static void __switch_pg(struct multipath *m, struct priority_group *pg)
+ __must_hold(&m->lock)
{
m->current_pg = pg;
@@ -355,8 +365,8 @@ static void __switch_pg(struct multipath *m, struct priority_group *pg)
static struct pgpath *choose_path_in_pg(struct multipath *m,
struct priority_group *pg,
size_t nr_bytes)
+ __must_hold(&m->lock)
{
- unsigned long flags;
struct dm_path *path;
struct pgpath *pgpath;
@@ -368,10 +378,8 @@ static struct pgpath *choose_path_in_pg(struct multipath *m,
if (unlikely(READ_ONCE(m->current_pg) != pg)) {
/* Only update current_pgpath if pg changed */
- spin_lock_irqsave(&m->lock, flags);
m->current_pgpath = pgpath;
__switch_pg(m, pg);
- spin_unlock_irqrestore(&m->lock, flags);
}
return pgpath;
@@ -381,7 +389,7 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
{
unsigned long flags;
struct priority_group *pg;
- struct pgpath *pgpath;
+ struct pgpath *pgpath, *res = NULL;
unsigned bypassed = 1;
if (!atomic_read(&m->nr_valid_paths)) {
@@ -419,6 +427,7 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
* Second time we only try the ones we skipped, but set
* pg_init_delay_retry so we do not hammer controllers.
*/
+ spin_lock_irqsave(&m->lock, flags);
do {
list_for_each_entry(pg, &m->priority_groups, list) {
if (pg->bypassed == !!bypassed)
@@ -427,18 +436,22 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
if (!IS_ERR_OR_NULL(pgpath)) {
if (!bypassed)
set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
- return pgpath;
+ res = pgpath;
+ break;
}
}
- } while (bypassed--);
+ } while (!res && bypassed--);
+ spin_unlock_irqrestore(&m->lock, flags);
failed:
spin_lock_irqsave(&m->lock, flags);
- m->current_pgpath = NULL;
- m->current_pg = NULL;
+ if (!res) {
+ m->current_pgpath = NULL;
+ m->current_pg = NULL;
+ }
spin_unlock_irqrestore(&m->lock, flags);
- return NULL;
+ return res;
}
/*
@@ -1875,6 +1888,7 @@ static int multipath_busy(struct dm_target *ti)
struct multipath *m = ti->private;
struct priority_group *pg, *next_pg;
struct pgpath *pgpath;
+ unsigned long flags;
/* pg_init in progress */
if (atomic_read(&m->pg_init_in_progress))
@@ -1906,6 +1920,7 @@ static int multipath_busy(struct dm_target *ti)
* will be able to select it. So we consider such a pg as not busy.
*/
busy = true;
+ spin_lock_irqsave(&m->lock, flags);
list_for_each_entry(pgpath, &pg->pgpaths, list) {
if (pgpath->is_active) {
has_active = true;
@@ -1915,6 +1930,7 @@ static int multipath_busy(struct dm_target *ti)
}
}
}
+ spin_unlock_irqrestore(&m->lock, flags);
if (!has_active) {
/*
--
2.15.1