[RFC] breakage in bsg - Kernel

This is a discussion on [RFC] breakage in bsg - Kernel ; * with "bsg: bind bsg to request_queue instead of gendisk" we get all requests with NULL ->rq_disk. SCSI can cope with that, anything else is not promised to be able to surive that. Indeed, quite a few drivers do not. ...

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Thread: [RFC] breakage in bsg

  1. [RFC] breakage in bsg

    * with "bsg: bind bsg to request_queue instead of gendisk" we
    get all requests with NULL ->rq_disk. SCSI can cope with that, anything
    else is not promised to be able to surive that. Indeed, quite a few
    drivers do not.

    * WTF are these per-bd flags doing, seeing that you set them
    on every ->read() and ->write()? Just what will happen if you have
    two openers?

    * cmd_filter thing is broken as well (we have no access to
    gendisk in question and there's a lot of obvious issues when you have
    several openers).

    #2 and part of #3 are fixable, but I really don't see what to do with #1.
    If nothing else, it's absolutely incompatible with cmd_filter, even if you
    leave aside the issue with non-IDE/non-SCSI drivers.

    Comments?
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  2. Re: [RFC] breakage in bsg

    On Sun, Jul 20, 2008 at 05:34:06PM +0100, Al Viro wrote:

    > * cmd_filter thing is broken as well (we have no access to
    > gendisk in question and there's a lot of obvious issues when you have
    > several openers).
    >
    > #2 and part of #3 are fixable, but I really don't see what to do with #1.
    > If nothing else, it's absolutely incompatible with cmd_filter, even if you
    > leave aside the issue with non-IDE/non-SCSI drivers.


    Actually, cmd_filter changeset breaks all users of blk_verify_command().
    It expects that struct file passed to will be that of a block device:
    inode = file->f_dentry->d_inode;
    if (!inode)
    return -EINVAL;

    disk = inode->i_bdev->bd_disk;

    return blk_cmd_filter_verify_command(&disk->cmd_filter,
    cmd, &file->f_mode);

    Unfortunately, all of those can get struct file of *character* device, with
    obvious results.

    The minimal fix is to pass disk / mode explicitly. I'll post the patch,
    but that still leaves bsg broken.
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