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SubjectRe: Kernel crashing on eject SD card
Hi,

Thank you for review and comments.

On 02/16/12 02:26, Tejun Heo wrote:
> On Wed, Feb 15, 2012 at 11:56:19AM +0900, Jun'ichi Nomura wrote:
>> +int invalidate_partitions(struct gendisk *disk, struct block_device *bdev)
>> +{
>> + int res;
>> +
>> + res = drop_partitions(disk, bdev);
>> + if (res)
>> + return res;
>> +
>
> Hmmm... shouldn't we have set_capacity(disk, 0) here?

Added.
I wasn't sure whether I should leave it to drivers.
But it seems capacity 0 for ENOMEDIUM device is reasonable.

>> + check_disk_size_change(disk, bdev);
>> + bdev->bd_invalidated = 0;
>> + /* tell userspace that the media / partition table may have changed */
>> + kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
>
> Also, we really shouldn't be generating KOBJ_CHANGE after every
> -ENOMEDIUM open. This can easily lead to infinite loop. We should
> generate this iff we actually dropped partitions && modified the size.

invalidate_partitions() is called only when bd_invalidated is set.
So KOBJ_CHANGE is not raised for every ENOMEDIUM open.

I put it explicit in the function to make it safer for
possible misuse.

How about this?

---------------------------------------------------------
Do not call drivers when invalidating partitions for -ENOMEDIUM
When a scsi driver returns -ENOMEDIUM for open(),
__blkdev_get() calls rescan_partitions(), which ends up calling
sd_revalidate_disk() without getting a refcount of scsi_device.

That could lead to oops like this:

process A process B
----------------------------------------------
sys_open
__blkdev_get
sd_open
returns -ENOMEDIUM
scsi_remove_device
<scsi_device torn down>
rescan_partitions
sd_revalidate_disk
<oops>
Oopses are reported here:
http://marc.info/?l=linux-scsi&m=132388619710052

This patch separates the partition invalidation from rescan_partitions()
and use it for -ENOMEDIUM case.

Index: linux-3.3/block/partition-generic.c
===================================================================
--- linux-3.3.orig/block/partition-generic.c 2012-02-15 09:00:25.147293790 +0900
+++ linux-3.3/block/partition-generic.c 2012-02-16 10:48:22.257680685 +0900
@@ -389,17 +389,11 @@ static bool disk_unlock_native_capacity(
}
}

-int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
+static int drop_partitions(struct gendisk *disk, struct block_device *bdev)
{
- struct parsed_partitions *state = NULL;
struct disk_part_iter piter;
struct hd_struct *part;
- int p, highest, res;
-rescan:
- if (state && !IS_ERR(state)) {
- kfree(state);
- state = NULL;
- }
+ int res;

if (bdev->bd_part_count)
return -EBUSY;
@@ -412,6 +406,24 @@ rescan:
delete_partition(disk, part->partno);
disk_part_iter_exit(&piter);

+ return 0;
+}
+
+int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
+{
+ struct parsed_partitions *state = NULL;
+ struct hd_struct *part;
+ int p, highest, res;
+rescan:
+ if (state && !IS_ERR(state)) {
+ kfree(state);
+ state = NULL;
+ }
+
+ res = drop_partitions(disk, bdev);
+ if (res)
+ return res;
+
if (disk->fops->revalidate_disk)
disk->fops->revalidate_disk(disk);
check_disk_size_change(disk, bdev);
@@ -515,6 +527,26 @@ rescan:
return 0;
}

+int invalidate_partitions(struct gendisk *disk, struct block_device *bdev)
+{
+ int res;
+
+ if (!bdev->bd_invalidated)
+ return 0;
+
+ res = drop_partitions(disk, bdev);
+ if (res)
+ return res;
+
+ set_capacity(disk, 0);
+ check_disk_size_change(disk, bdev);
+ bdev->bd_invalidated = 0;
+ /* tell userspace that the media / partition table may have changed */
+ kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
+
+ return 0;
+}
+
unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)
{
struct address_space *mapping = bdev->bd_inode->i_mapping;
Index: linux-3.3/include/linux/genhd.h
===================================================================
--- linux-3.3.orig/include/linux/genhd.h 2012-02-09 12:21:53.000000000 +0900
+++ linux-3.3/include/linux/genhd.h 2012-02-16 10:47:43.783681813 +0900
@@ -596,6 +596,7 @@ extern char *disk_name (struct gendisk *

extern int disk_expand_part_tbl(struct gendisk *disk, int target);
extern int rescan_partitions(struct gendisk *disk, struct block_device *bdev);
+extern int invalidate_partitions(struct gendisk *disk, struct block_device *bdev);
extern struct hd_struct * __must_check add_partition(struct gendisk *disk,
int partno, sector_t start,
sector_t len, int flags,
Index: linux-3.3/fs/block_dev.c
===================================================================
--- linux-3.3.orig/fs/block_dev.c 2012-02-09 12:21:53.000000000 +0900
+++ linux-3.3/fs/block_dev.c 2012-02-16 10:47:52.602681441 +0900
@@ -1183,8 +1183,12 @@ static int __blkdev_get(struct block_dev
* The latter is necessary to prevent ghost
* partitions on a removed medium.
*/
- if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
- rescan_partitions(disk, bdev);
+ if (bdev->bd_invalidated) {
+ if (!ret)
+ rescan_partitions(disk, bdev);
+ else if (ret == -ENOMEDIUM)
+ invalidate_partitions(disk, bdev);
+ }
if (ret)
goto out_clear;
} else {
@@ -1214,8 +1218,12 @@ static int __blkdev_get(struct block_dev
if (bdev->bd_disk->fops->open)
ret = bdev->bd_disk->fops->open(bdev, mode);
/* the same as first opener case, read comment there */
- if (bdev->bd_invalidated && (!ret || ret == -ENOMEDIUM))
- rescan_partitions(bdev->bd_disk, bdev);
+ if (bdev->bd_invalidated) {
+ if (!ret)
+ rescan_partitions(bdev->bd_disk, bdev);
+ else if (ret == -ENOMEDIUM)
+ invalidate_partitions(bdev->bd_disk, bdev);
+ }
if (ret)
goto out_unlock_bdev;
}

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