Re: [Xen-devel] [PATCH] grant table map error in __gnttab_map_grant_ref

["Jan Beulich" <JBeulich@xxxxxxxx>]

   >>> On 04.02.12 at 03:43, Liuyongan <liuyongan@xxxxxxxxxx> wrote:
> In file grant_table.c function __gnttab_map_grant_ref, if __get_paged_frame 
> failed, the effect of _set_status  previously called should be rollback, so 
> the flag GTF_reading and _GTF_writing will be recovered. 

Not knowing too much about these, but isn't __acquire_grant_for_copy()
in need of a similar adjustment?

Further, aren't the status flags cumulative (and hence isn't it wrong to
simply clear flags without considering their original state)? (I realize
that this is not a new issue introduced with the proposed patch, but
certainly with more ways of getting that code path run through, it
becomes more important for it to be correct.)

Jan

> Signed-off-by: Haoyu Zhang<haoyu.zhang@xxxxxxxxxx>; Liang 
> Wang<hzwangliang.wang@xxxxxxxxxx>
> 
> diff -r cbed91e1c878 xen-4.1.2/xen/common/grant_table.c
> --- a/xen-4.1.2/xen/common/grant_table.c      Sat Feb 04 18:36:13 2012 +0800
> +++ b/xen-4.1.2/xen/common/grant_table.c      Sat Feb 04 18:40:02 2012 +0800
> @@ -566,7 +566,7 @@
>              gfn = sha1 ? sha1->frame : sha2->full_page.frame;
>              rc = __get_paged_frame(gfn, &frame, !!(op->flags & 
> GNTMAP_readonly), rd);
>              if ( rc != GNTST_okay )
> -                goto unlock_out;
> +                goto unlock_out_clear;
>              act->gfn = gfn;
>              act->domid = ld->domain_id;
>              act->frame = frame;
> @@ -721,7 +721,8 @@
>      if ( op->flags & GNTMAP_host_map )
>          act->pin -= (op->flags & GNTMAP_readonly) ?
>              GNTPIN_hstr_inc : GNTPIN_hstw_inc;
> -
> + 
> + unlock_out_clear:
>      if ( !(op->flags & GNTMAP_readonly) &&
>           !(act->pin & (GNTPIN_hstw_mask|GNTPIN_devw_mask)) )
>          gnttab_clear_flag(_GTF_writing, status);




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