lkml.org 
[lkml]   [2020]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: use case for register_pstore_blk?
    On Wed, Oct 07, 2020 at 08:42:58PM +0200, Christoph Hellwig wrote:
    > The problem with the block code is that it is completely broken.

    This seems like hyperbole.

    > It uses on-stack structures where it can't,

    Do you mean the ones in pstore_blk_init() and pstore_blk_exit()? Those
    are fine -- they're what provide the "driverless" module-param loaded
    "best_effort" target. Do you seem something unsafe about it?

    > it pokes into internals of the block device read/write path for
    > absolutely no reason,

    Do you mean psblk_generic_blk_read() and psblk_generic_blk_write()?
    These are for writing to the block device... I'm happy to adjust this
    if you can show me the better API. (This was being developed in the
    middle of the iov_iter changes, so perhaps I missed a more appropriate
    way to do things.)

    > and it uses name_to_dev_t which must not be used in new code.

    What?

    include/linux/mount.h:
    extern dev_t name_to_dev_t(const char *name);

    init/do_mounts.c:
    /*
    * Convert a name into device number. We accept the following
    * variants:
    ...
    * If name doesn't have fall into the categories above, we return
    * (0,0).
    * block_class is used to check if something is a disk name. If the
    * disk
    * name contains slashes, the device name has them replaced with
    * bangs.
    */
    dev_t name_to_dev_t(const char *name)

    There are no comments about it being deprecated.

    And even I had guessed to double-check, there isn't even a hit
    on lkml about it that I can easily find:
    https://lore.kernel.org/lkml/?q=name_to_dev_t+%22new+code%22
    https://lore.kernel.org/lkml/?q=name_to_dev_t+deprecated

    Where did this happen, where was it documented, and what should be used
    instead?

    > Or in other words: it is a complete piece of crap full of layering
    > violations that should never have been merged in that form.

    Gee thanks. I obviously don't agree with you.

    > It also does not happen to share code with the mtd case.

    What? Yes it does: it explicitly uses the pstore/blk configuration
    callback to get the details configured at boot to identify and configure
    the backing device. This is specifically designed this way to avoid
    repeating the mistake of having per-backing-device configuration that is
    essentially only actually used by the pstore storage layer. i.e. the very
    thing I'm trying to get away from in ramoops, efi-pstore, etc: storage
    configuration is tied to the pstore storage layer (i.e. pstore/blk and
    pstore/zone), not the specific backing device (i.e. MTD, blk, RAM, NVRAM,
    EFI variables, etc).

    So, yes, I think it'd be fine to drop the unused EXPORTs, and I welcome
    corrections to the generic read/write routines, I very specifically do
    not want to rip out having a block device as a backing device, nor do I
    want to revert the configuration management to being backing device
    specific.

    --
    Kees Cook

    \
     
     \ /
      Last update: 2020-10-07 21:18    [W:3.102 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site