lkml.org 
[lkml]   [2023]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v2] Revert "fuse: Apply flags2 only when userspace set the FUSE_INIT_EXT"
    Date
    On 10/18/23 16:26, André Draszik wrote:
    > On Wed, 2023-10-18 at 11:52 +0000, Bernd Schubert wrote:
    >> On 10/18/23 13:46, André Draszik wrote:
    >>> On Wed, 2023-10-18 at 11:39 +0000, Bernd Schubert wrote:
    >>>> On 10/18/23 13:15, André Draszik wrote:
    >>>>> From: André Draszik <andre.draszik@linaro.org>
    >>>>>
    >>>>> This reverts commit 3066ff93476c35679cb07a97cce37d9bb07632ff.
    >>>>>
    >>>>> This patch breaks all existing userspace by requiring updates
    >>>>> as
    >>>>> mentioned in the commit message, which is not allowed.
    >>>>>
    >>>>> Revert to restore compatibility with existing userspace
    >>>>> implementations.
    >>>>
    >>>> Which fuse file system does it exactly break? In fact there
    >>>> haven't
    >>>> been
    >>>> added too many flags after - what exactly is broken?
    >>>
    >>> The original patch broke the existing kernel <-> user ABI by now
    >>> requiring user space applications to pass in an extra flag.
    >>> There are various side-effects of this, like unbootable systems,
    >>> just
    >>> because the kernel was updated.
    >>> Breaking the ABI is the one thing that is not allowed. This is not
    >>> specific to any particular fuse file system.
    >>
    >> How exactly did it break it?
    >
    > At least in Android, creating new files, or reading existing files
    > returns -EFAULT

    Hmm, could you please point me to the corresponding android userspace
    library? I guess it is not using libfuse? At least I would like to
    understand the issue...

    >
    >> These are feature flags - is there really a
    >> file system that relies on these flag to the extend that it does not
    >> work anymore?
    >
    > I don't know enough about the implementation details, but even outside
    > Android user space had to be updated as a prerequisite for this kernel
    > patch:
    > https://lore.kernel.org/all/YmUKZQKNAGimupv7@redhat.com/
    > https://github.com/libfuse/libfuse/pull/662
    >
    > Which means any non-Android user space predating those changes isn't
    > working anymore either.

    The patch in libfuse is from me, there was nothing broken.
    And I don't think that any of the additional flags added are a
    _requirement_ for libfuse file systems to work. I'm not sure if DAX and
    the other flags before the patch was merged are a _requirement_ for
    virtiofsd or just a nice feature to have...

    In anyway, please still consider that using possibly uninitialized flags
    is not a good idea either and could randomly break things as well.


    Thanks,
    Bernd


    \
     
     \ /
      Last update: 2023-10-18 16:41    [W:3.295 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site