"Jinu M." <jinum@esntechnologies.co.in> wrote:
>
> Hi All,
>
> We are developing a storage driver (block driver) on 2.6.x kernel. The
> hardware we are using supports media removal on the fly. We are facing
> some problem when the media is removed while the disk is mounted. The
> system freezes and the module count never goes to zero.
>
> This is what we do when the disk is removed on the fly.
>
> disk_removed(...)
> {
> /* invalidate disk */
> if(gDisk->bdev) {
> invalidate_bdev(gDisk->bdev, 1);
> bdput(gDisk->bdev);
> }
>
> /* indicates that no disk present */
> set_capacity(gDisk->gd, 0);
>
> /* cleanup gendisk */
> del_gendisk(gDisk->gd);
> put_disk(gDisk->gd);
>
> /* clean up blkqueue */
> blk_cleanup_queue(gDisk->blkqueue);
> }
>
> disk_removed() is called from the workqueue that is initiated from the
> tasklet()<=isr() on card removal.
>
> We guess invalidate_bdev() is the culprit ;) but would like to know
> from you all if we are doing some mistake. Is there something missing
> or something wrong in the way we are trying to provide removable media
> support?
>
afaik we don't really support hot unplug like this.
Changes were made a few months ago (make the VFS use file->f_mapping rather
than file->f_dentry->d_inode->i_mapping) which set some of the pieces in
place but I think there's a way to go yet.
umm, the general idea is that when the disk vanishes your driver should
then return -EIO for all future I/O requests. The block_device, the queue,
the inode and all that stuff remains in-core.
After device hot unplug we need to do <something> to disassociate the
defunct blockdev inode from the /dev/hdXX node. I think <something> hasn't
been coded yet.
Later, someone puts in new media and you can then access that via /dev/hdXX
- you get a brand new inode, blockdev, queue, etc. The old defunct one is
still alive, returning -EIO.
Eventually, all references to the old inode/blockdev/queue go away (due to
applications hitting EIO, etc). The old mountpoint can be unmounted and
this drops the final ref, so the old inode/blockdev/queue get freed up.
As I say, I don't think all of this is implemented yet, but perhaps a lot
of it is.
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