In brd_init func, rd_nr num of brd_device are firstly allocated
and add in brd_devices, then brd_devices are traversed to add each
brd_device by calling add_disk func. When allocating brd_device,
the disk->first_minor is set to i * max_part, if rd_nr * max_part
is larger than MINORMASK, two different brd_device may have the same
devt, then only one of them can be successfully added.
when rmmod brd.ko, it will cause oops when calling brd_exit.
Follow those steps:
# modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
# rmmod brd
then, the oops will appear.
Oops log:
[ 726.613722] Call trace:
[ 726.614175] kernfs_find_ns+0x24/0x130
[ 726.614852] kernfs_find_and_get_ns+0x44/0x68
[ 726.615749] sysfs_remove_group+0x38/0xb0
[ 726.616520] blk_trace_remove_sysfs+0x1c/0x28
[ 726.617320] blk_unregister_queue+0x98/0x100
[ 726.618105] del_gendisk+0x144/0x2b8
[ 726.618759] brd_exit+0x68/0x560 [brd]
[ 726.619501] __arm64_sys_delete_module+0x19c/0x2a0
[ 726.620384] el0_svc_common+0x78/0x130
[ 726.621057] el0_svc_handler+0x38/0x78
[ 726.621738] el0_svc+0x8/0xc
[ 726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
Here, we add brd_check_and_reset_par func to check and limit max_part par.
--
V4->V5:(suggested by Ming Lei)
- make sure max_part is not larger than DISK_MAX_PARTS
V3->V4:(suggested by Ming Lei)
- remove useless change
- add one limit of max_part
V2->V3: (suggested by Ming Lei)
- clear .minors when running out of consecutive minor space in brd_alloc
- remove limit of rd_nr
V1->V2:
- add more checks in brd_check_par_valid as suggested by Ming Lei.
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
Reviewed-by: Bob Liu <bob.liu@xxxxxxxxxx>
---
drivers/block/brd.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index df8103dd40ac..6b9db3f63cb7 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -389,11 +389,12 @@ static struct brd_device *brd_alloc(int i)
* is harmless)
*/
blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
- disk = brd->brd_disk = alloc_disk(max_part);
+ disk = brd->brd_disk = alloc_disk(((i * max_part) & ~MINORMASK) ?
+ 0 : max_part);
if (!disk)
goto out_free_queue;
disk->major = RAMDISK_MAJOR;
- disk->first_minor = i * max_part;
+ disk->first_minor = i * disk->minors;
disk->fops = &brd_fops;
disk->private_data = brd;
disk->queue = brd->brd_queue;
@@ -468,6 +469,25 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
return kobj;
}
+static inline void brd_check_and_reset_par(void)
+{
+ if (unlikely(!max_part))
+ max_part = 1;
+
+ /*
+ * make sure 'max_part' can be divided exactly by (1U << MINORBITS),
+ * otherwise, it is possiable to get same dev_t when adding partitions.
+ */
+ if ((1U << MINORBITS) % max_part != 0)
+ max_part = 1UL << fls(max_part);
+
+ if (max_part > DISK_MAX_PARTS) {
+ pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n",
+ DISK_MAX_PARTS, DISK_MAX_PARTS);
+ max_part = DISK_MAX_PARTS;
+ }
+}
+
static int __init brd_init(void)
{
struct brd_device *brd, *next;
@@ -491,8 +511,7 @@ static int __init brd_init(void)
if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
return -EIO;
- if (unlikely(!max_part))
- max_part = 1;
+ brd_check_and_reset_par();
for (i = 0; i < rd_nr; i++) {
brd = brd_alloc(i);
--
2.19.1
