Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for __insert_vmap_area()

From	David Rientjes <rientjes@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for __insert_vmap_area()
Date	2016-09-22 00:50 +0200
Message-ID	<sjYuZ-6wT-5@gated-at.bofh.it> (permalink)
References	<sjHkt-4fQ-1@gated-at.bofh.it> <sjX5T-5Jq-1@gated-at.bofh.it> <sjYlk-6tw-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Thu, 22 Sep 2016, zijun_hu wrote:

> >> correct a few logic error for __insert_vmap_area() since the else
> >> if condition is always true and meaningless
> >>
> >> in order to fix this issue, if vmap_area inserted is lower than one
> >> on rbtree then walk around left branch; if higher then right branch
> >> otherwise intersects with the other then BUG_ON() is triggered
> >>
> > 
> > Under normal operation, you're right that the "else if" conditional should 
> > always succeed: we don't want to BUG() unless there's a bug.  The original 
> > code can catch instances when va->va_start == tmp_va->va_end where we 
> > should BUG().  Your code silently ignores it.
> > 
> Hmm, the BUG_ON() appears in the original code, i don't introduce it.
> it maybe be better to consider va->va_start == tmp_va->va_end as normal case
> and should not BUG_ON() it since the available range of vmap_erea include
> the start boundary but the end, BTW, represented as [start, end)
> 

We don't support inserting when va->va_start == tmp_va->va_end, plain and 
simple.  There's no reason to do so.  NACK to the patch.

Thread

[PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() zijun_hu <zijun_hu@zoho.com> - 2016-09-21 06:30 +0200
  Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() David Rientjes <rientjes@google.com> - 2016-09-21 23:20 +0200
    Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() zijun_hu <zijun_hu@zoho.com> - 2016-09-22 00:40 +0200
      Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() David Rientjes <rientjes@google.com> - 2016-09-22 00:50 +0200
        Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() David Rientjes <rientjes@google.com> - 2016-09-22 01:20 +0200
          Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() zijun_hu <zijun_hu@zoho.com> - 2016-09-22 02:00 +0200
        Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() zijun_hu <zijun_hu@zoho.com> - 2016-09-22 01:20 +0200
  Re: [RFC PATCH 1/5] mm/vmalloc.c: correct a few logic error for  __insert_vmap_area() zijun_hu <zijun_hu@zoho.com> - 2016-09-22 03:40 +0200

csiph-web