Getting debugfs mountpoint?

Getting debugfs mountpoint?

[Jacob Sowles]

Is there an easy way to get the path to where debugfs is mounted? I
found a function called debugfs_find_mountpoint(), which is exactly
what I want, but it’s not exported, so I can’t use it. The only
exported debugfs functions that I could find are the ones that create,
remove, etc.

Jacob

Re: Getting debugfs mountpoint?

[Al Viro]

On Fri, Sep 14, 2012 at 06:49:01PM -0700, Jacob Sowles wrote:
> Is there an easy way to get the path to where debugfs is mounted? I
> found a function called debugfs_find_mountpoint(), which is exactly
> what I want, but it’s not exported, so I can’t use it. The only
> exported debugfs functions that I could find are the ones that create,
> remove, etc.

More to the point, it's a userland function.  Why would you want that
kernel-side?

Re: Getting debugfs mountpoint?

[Jacob Sowles]

Multiple instances of my code can be run simultaneously, and all
instances use the same debugfs directory, so I need the path to the
debugfs root directory so that I can use filp_open to get the dentry
for that directory.

Jacob

On Fri, Sep 14, 2012 at 6:57 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, Sep 14, 2012 at 06:49:01PM -0700, Jacob Sowles wrote:
>> Is there an easy way to get the path to where debugfs is mounted? I
>> found a function called debugfs_find_mountpoint(), which is exactly
>> what I want, but it’s not exported, so I can’t use it. The only
>> exported debugfs functions that I could find are the ones that create,
>> remove, etc.
>
> More to the point, it's a userland function.  Why would you want that
> kernel-side?

Re: Getting debugfs mountpoint?

[Al Viro]

On Fri, Sep 14, 2012 at 07:07:43PM -0700, Jacob Sowles wrote:
> Multiple instances of my code can be run simultaneously, and all
> instances use the same debugfs directory, so I need the path to the
> debugfs root directory so that I can use filp_open to get the dentry
> for that directory.

What's wrong with just storing a pointer to that dentry in a variable?
And what do you want an opened file (of a directory, at that) on debugfs?

Re: Getting debugfs mountpoint?

[Jacob Sowles]

The first instance of my code calls debugfs_create_file and stores a
pointer to the dentry of that directory. But when the second instance
calls debugfs_create_file, the function returns NULL because that
directory already exists, so it doesn't return the dentry that I need.

On Fri, Sep 14, 2012 at 7:11 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, Sep 14, 2012 at 07:07:43PM -0700, Jacob Sowles wrote:
>> Multiple instances of my code can be run simultaneously, and all
>> instances use the same debugfs directory, so I need the path to the
>> debugfs root directory so that I can use filp_open to get the dentry
>> for that directory.
>
> What's wrong with just storing a pointer to that dentry in a variable?
> And what do you want an opened file (of a directory, at that) on debugfs?

Re: Getting debugfs mountpoint?

[Jacob Sowles]

debugfs_create_dir, rather. Not debugfs_create_file.

On Fri, Sep 14, 2012 at 7:17 PM, Jacob Sowles <sowlesj@gmail.com> wrote:
> The first instance of my code calls debugfs_create_file and stores a
> pointer to the dentry of that directory. But when the second instance
> calls debugfs_create_file, the function returns NULL because that
> directory already exists, so it doesn't return the dentry that I need.
>
> On Fri, Sep 14, 2012 at 7:11 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>> On Fri, Sep 14, 2012 at 07:07:43PM -0700, Jacob Sowles wrote:
>>> Multiple instances of my code can be run simultaneously, and all
>>> instances use the same debugfs directory, so I need the path to the
>>> debugfs root directory so that I can use filp_open to get the dentry
>>> for that directory.
>>
>> What's wrong with just storing a pointer to that dentry in a variable?
>> And what do you want an opened file (of a directory, at that) on debugfs?

Re: Getting debugfs mountpoint?

[Al Viro]

On Fri, Sep 14, 2012 at 07:17:12PM -0700, Jacob Sowles wrote:
> The first instance of my code calls debugfs_create_file and stores a
> pointer to the dentry of that directory. But when the second instance
> calls debugfs_create_file, the function returns NULL because that
> directory already exists, so it doesn't return the dentry that I need.

... and?  Ever heard of that thing called "global variable"?

Re: Getting debugfs mountpoint?

[Rob Landley]

>From userspace? Something like:

  grep " debugfs " /proc/mounts | awk '{print $2}' | xargs echo -e

>From kernel space? There isn't guaranteed to be _one_, you can mount
multiple instances of most filesystems, and with container support you can
even have multiple debugfs superblocks.

Rob

On Fri, Sep 14, 2012 at 8:49 PM, Jacob Sowles <sowlesj@gmail.com> wrote:
> Is there an easy way to get the path to where debugfs is mounted? I
> found a function called debugfs_find_mountpoint(), which is exactly
> what I want, but it’s not exported, so I can’t use it. The only
> exported debugfs functions that I could find are the ones that create,
> remove, etc.
>
> Jacob
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