On Thu, 19 May 2011, Eric Sandeen wrote:
> On 5/9/11 10:57 AM, Lukas Czerner wrote:
> > We need to take reference to the s_li_request after we take a mutex,
> > because it might be freed since then, hence result in accessing old
> > already freed memory. Also we should protect the whole
> > ext4_remove_li_request() because ext4_li_info might be in the process of
> > being freed in ext4_lazyinit_thread().
>
> It'd be really great to have some comments which explain just what
> ext4_li_mtx protects, but I'm working on an add-comments patch for
> the lazyinit stuff (I commented things a bit as I reviewed your
> changes) so I'll send that along later.
The ext4_li_mtx is protecting the whole ext4_li_info structure so it can
be atomically created and freed.
>
> in any case, the change looks ok, thanks.
>
> Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Thanks!
-Lukas
>
>
> > Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> > ---
> > fs/ext4/super.c | 10 ++++++----
> > 1 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index c379af6..6a8e48f 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -2721,14 +2721,16 @@ static void ext4_remove_li_request(struct ext4_li_request *elr)
> >
> > static void ext4_unregister_li_request(struct super_block *sb)
> > {
> > - struct ext4_li_request *elr = EXT4_SB(sb)->s_li_request;
> > -
> > - if (!ext4_li_info)
> > + mutex_lock(&ext4_li_mtx);
> > + if (!ext4_li_info) {
> > + mutex_unlock(&ext4_li_mtx);
> > return;
> > + }
> >
> > mutex_lock(&ext4_li_info->li_list_mtx);
> > - ext4_remove_li_request(elr);
> > + ext4_remove_li_request(EXT4_SB(sb)->s_li_request);
> > mutex_unlock(&ext4_li_info->li_list_mtx);
> > + mutex_unlock(&ext4_li_mtx);
> > }
> >
> > static struct task_struct *ext4_lazyinit_task;
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
