Re: [PATCH v5 1/2] fs: rename vfs_get_super() to get_tree_super() and export it

[Giuseppe Scrivano <gscrivan@redhat.com>]

Gao Xiang <xiang@kernel.org> writes:

> (+ cc vfs maintainers)
>
> Hi,
>
> On Tue, Aug 11, 2026 at 09:10:50AM +0200, Giuseppe Scrivano wrote:
>> vfs_get_super() already implements the common get_tree pattern of
>> looking up an existing superblock via a test callback and initialising
>> a new one with fill_super otherwise, but it is private to fs/super.c
>> and only reachable through the get_tree_nodev()/get_tree_single()/
>> get_tree_keyed() wrappers, none of which let a filesystem supply its
>> own test callback.
>> 
>> Rename it to get_tree_super() and export it so filesystems that need a
>> custom superblock matching policy can reuse it directly instead of
>> open-coding sget_fc() + fill_super().  No functional change.
>> 
>> This is a preparatory fix for the next patch.
>> 
>> Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
>
> With the new vfs_get_super() helper, it seems much cleaner compared
> to the previous versions.
>
> Since this series interacts with the other erofs ongoing patches.
> So I hope at least [PATCH 2/2] can be routed into the erofs tree to
> avoid unnecessary conflict resolving.
>
> Maybe the simplistic way is vfs maintainers can ack this vfs patch so
> that both patches can go through erofs tree for the next cycle
> directly.
>
>
>> ---
>
> ...
>
>> +/**
>> + * get_tree_super - Get a superblock, optionally sharing an existing one
>> + * @fc: The filesystem context holding the parameters
>> + * @test: Comparison function to find a matching existing superblock, or NULL
>> + * @fill_super: Helper to initialise a new superblock
>> + *
>> + * If @test is non-NULL and matches an existing superblock, that superblock is
>> + * reused; otherwise a new anonymous superblock is created and initialised with
>> + * @fill_super.  Passing NULL for @test always creates a new superblock.
>> + */
>> +int get_tree_super(struct fs_context *fc,
>>  		int (*test)(struct super_block *, struct fs_context *),
>>  		int (*fill_super)(struct super_block *sb,
>>  				  struct fs_context *fc))
>> @@ -1278,12 +1288,13 @@ static int vfs_get_super(struct fs_context *fc,
>>  	deactivate_locked_super(sb);
>>  	return err;
>>  }
>> +EXPORT_SYMBOL(get_tree_super);
>
> btw, some people prefer EXPORT_SYMBOL_GPL() for this kind of helpers.

I am fine with this change, but the rest of the file is using
EXPORT_SYMBOL though, that is why I've used it.

Regards,
Giuseppe