From: Li Nan linan122@huawei.com
[ Upstream commit 03f12122b20b6e6028e9ed69030a49f9cffcbb75 ]
'open_mutex' of gendisk is used to protect open/close block devices. But in bd_link_disk_holder(), it is used to protect the creation of symlink between holding disk and slave bdev, which introduces some issues.
When bd_link_disk_holder() is called, the driver is usually in the process of initialization/modification and may suspend submitting io. At this time, any io hold 'open_mutex', such as scanning partitions, can cause deadlocks. For example, in raid:
T1 T2 bdev_open_by_dev lock open_mutex [1] ... efi_partition ... md_submit_bio md_ioctl mddev_syspend -> suspend all io md_add_new_disk bind_rdev_to_array bd_link_disk_holder try lock open_mutex [2] md_handle_request -> wait mddev_resume
T1 scan partition, T2 add a new device to raid. T1 waits for T2 to resume mddev, but T2 waits for open_mutex held by T1. Deadlock occurs.
Fix it by introducing a local mutex 'blk_holder_mutex' to replace 'open_mutex'.
Fixes: 1b0a2d950ee2 ("md: use new apis to suspend array for ioctls involed array reconfiguration") Reported-by: mgperkow@gmail.com Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218459 Signed-off-by: Li Nan linan122@huawei.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Yu Kuai yukuai3@huawei.com Link: https://lore.kernel.org/r/20240221090122.1281868-1-linan666@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/holder.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/block/holder.c b/block/holder.c index 37d18c13d9581..791091a7eac23 100644 --- a/block/holder.c +++ b/block/holder.c @@ -8,6 +8,8 @@ struct bd_holder_disk { int refcnt; };
+static DEFINE_MUTEX(blk_holder_mutex); + static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev, struct gendisk *disk) { @@ -80,7 +82,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) kobject_get(bdev->bd_holder_dir); mutex_unlock(&bdev->bd_disk->open_mutex);
- mutex_lock(&disk->open_mutex); + mutex_lock(&blk_holder_mutex); WARN_ON_ONCE(!bdev->bd_holder);
holder = bd_find_holder_disk(bdev, disk); @@ -108,7 +110,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) goto out_del_symlink; list_add(&holder->list, &disk->slave_bdevs);
- mutex_unlock(&disk->open_mutex); + mutex_unlock(&blk_holder_mutex); return 0;
out_del_symlink: @@ -116,7 +118,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) out_free_holder: kfree(holder); out_unlock: - mutex_unlock(&disk->open_mutex); + mutex_unlock(&blk_holder_mutex); if (ret) kobject_put(bdev->bd_holder_dir); return ret; @@ -140,7 +142,7 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) if (WARN_ON_ONCE(!disk->slave_dir)) return;
- mutex_lock(&disk->open_mutex); + mutex_lock(&blk_holder_mutex); holder = bd_find_holder_disk(bdev, disk); if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { del_symlink(disk->slave_dir, bdev_kobj(bdev)); @@ -149,6 +151,6 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) list_del_init(&holder->list); kfree(holder); } - mutex_unlock(&disk->open_mutex); + mutex_unlock(&blk_holder_mutex); } EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);