在 2024/2/8 14:50, Song Liu 写道:
On Wed, Feb 7, 2024 at 1:32 AM <linan666@xxxxxxxxxxxxxxx> wrote:
From: Li Nan <linan122@xxxxxxxxxx>
'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 'holder_mutex' to replace 'open_mutex'.
Is this to fix [1]? Do we need some Fixes and/or Closes tags?
No. Just use another way to fix [2], and both [2] and this patch can fix
the issue. I am not sure about the root cause of [1] yet.
[2] https://patchwork.kernel.org/project/linux-raid/list/?series=812045
Could you please add steps to reproduce this issue?
We need to modify the kernel, add sleep in md_submit_bio() and md_ioctl()
as below, and then:
1. mdadm -CR /dev/md0 -l1 -n2 /dev/sd[bc] #create a raid
2. echo 1 > /sys/module/md_mod/parameters/error_inject #enable sleep
3. 'mdadm --add /dev/md0 /dev/sda' #add a disk to raid
4. submit ioctl BLKRRPART to raid within 10s.
Changes of kernel:
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 350f5b22ba6f..ce16d319edf2 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -76,6 +76,8 @@ static DEFINE_SPINLOCK(pers_lock);
static const struct kobj_type md_ktype;
+static bool error_inject = false;
+
struct md_cluster_operations *md_cluster_ops;
EXPORT_SYMBOL(md_cluster_ops);
static struct module *md_cluster_mod;
@@ -372,6 +374,8 @@ static bool is_suspended(struct mddev *mddev, struct
bio *bio)
void md_handle_request(struct mddev *mddev, struct bio *bio)
{
+ if (error_inject)
+ ssleep(10);
check_suspended:
if (is_suspended(mddev, bio)) {
DEFINE_WAIT(__wait);
@@ -7752,6 +7756,8 @@ static int md_ioctl(struct block_device *bdev,
blk_mode_t mode,
*/
if (mddev->pers) {
mdu_disk_info_t info;
+ if (error_inject)
+ ssleep(10);
if (copy_from_user(&info, argp, sizeof(info)))
err = -EFAULT;
else if (!(info.state & (1<<MD_DISK_SYNC)))
@@ -10120,6 +10126,7 @@ module_param_call(start_ro, set_ro, get_ro, NULL,
S_IRUSR|S_IWUSR);
module_param(start_dirty_degraded, int, S_IRUGO|S_IWUSR);
module_param_call(new_array, add_named_array, NULL, NULL, S_IWUSR);
module_param(create_on_open, bool, S_IRUSR|S_IWUSR);
+module_param(error_inject, bool, S_IRUSR|S_IWUSR);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("MD RAID framework");
--
Thanks,
Nan
