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SubjectRe: Kernel crashing on eject SD card
Hi,

On Thu, Feb 16, 2012 at 10:26:38AM +0900, Jun'ichi Nomura wrote:
> 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?

Are there any updates on this fix? I was wondering if any progress has been
made and if this patch has any chances of hitting mainline soon.

I have executed a quick test and it seems to solve the problem (or, at least, I
am not able to reproduce the oops anymore).

Cheers,
--
Luis

> ---------------------------------------------------------
> 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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