Re: [uml-devel] UML hostfs bugs

[Blaisorblade <blaisorblade@yahoo.it>]

On Monday 14 August 2006 13:07, wang lianwei wrote:
> Answers:
>
> 1. I test it on ext3 filesystem.
>
> 2. You are right. Sometimes the pos telldir returned is not the next entry
> offset. just as your point out:
>       position 0 -> readdir "." -> you call telldir -> it _again_ says
> you're at 0.
>
> 3. I also try to resolve it by remove the seekdir(only use the
> sequence readdir call), It is also worked.

I can guess what the patch does but please generate with the additional -p 
option so it's easier to read (otherwise the recipient _has_ to read the 
source). Compliments for the solution, it's really simpler and better than my 
proposal.

Also, you have to regenerate it anyway for another (tiny) reason: it is not 
always safe to use "seekdir" in kernelspace code, you need (sadly) a new 
wrapper in hostfs_user.c and to call it instead of seekdir in hostfs_kern.c; 
almost surely you'll get an "undeclared function" warning but miscompilations 
in some rare cases are also possible, say for stat(): it is defined almost 
only as a static inline function, or for some structures having different 
definitions in userspace and kernelspace.

> --- linux-2.6.x/fs/hostfs/hostfs_kern.c 2006-04-12 15:12:51.000000000 +0800
> +++ linux-2.6.10-src/fs/hostfs/hostfs_kern.c      2006-08-14 18:25:
> 13.772237744 +0800
> @@ -338,6 +338,7 @@
>         kfree(name);
>         if(dir == NULL) return(-error);
>         next = file->f_pos;
> +       seekdir(dir,next);
>         while((name = read_dir(dir, &next, &ino, &len)) != NULL){
>                 error = (*filldir)(ent, name, len, file->f_pos,
>                                    ino, DT_UNKNOWN);
>
>
> --- linux-2.6.x/fs/hostfs/hostfs_user.c 2006-04-12 15:12:52.000000000 +0800
> +++ linux-2.6.10-src/fs/hostfs/hostfs_user.c      2006-08-14 18:36:
> 24.276305632 +0800
> @@ -122,7 +122,6 @@
>         DIR *dir = stream;
>         struct dirent *ent;
>
> -       seekdir(dir, *pos);
>         ent = readdir(dir);
>         if(ent == NULL) return(NULL);
>         *len_out = strlen(ent->d_name);

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
 http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com 


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