summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorAhmed S. Darwish <a.darwish@linutronix.de>2020-06-03 16:49:48 +0200
committerJens Axboe <axboe@kernel.dk>2020-06-04 21:22:28 -0600
commit15b81ce5abdc4b502aa31dff2d415b79d2349d2f (patch)
tree33b5c887643b18efec05f05d65749d0e79af59ac
parentd24de76af836260a99ca2ba281a937bd5bc55591 (diff)
block: nr_sects_write(): Disable preemption on seqcount write
For optimized block readers not holding a mutex, the "number of sectors" 64-bit value is protected from tearing on 32-bit architectures by a sequence counter. Disable preemption before entering that sequence counter's write side critical section. Otherwise, the read side can preempt the write side section and spin for the entire scheduler tick. If the reader belongs to a real-time scheduling class, it can spin forever and the kernel will livelock. Fixes: c83f6bf98dc1 ("block: add partition resize function to blkpg ioctl") Cc: <stable@vger.kernel.org> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/blk.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/block/blk.h b/block/blk.h
index aa16e524dc35..b5d1f0fc6547 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -420,9 +420,11 @@ static inline sector_t part_nr_sects_read(struct hd_struct *part)
static inline void part_nr_sects_write(struct hd_struct *part, sector_t size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+ preempt_disable();
write_seqcount_begin(&part->nr_sects_seq);
part->nr_sects = size;
write_seqcount_end(&part->nr_sects_seq);
+ preempt_enable();
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
preempt_disable();
part->nr_sects = size;