| Message ID | 20200412143803.43931-1-fishland@aliyun.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] mm/vmalloc: make sure to traverse from the beginning when overflow occur | expand |
On 4/12/20 7:38 AM, Liu Song wrote: > If overflow, should ensure that "free_vmap_cache" is set to NULL, > so as to ensure that it can be traversed from the beginning. This changelog is a bit sparse. Does this fix a demonstrated problem? Or was it just discovered via code review and assumed to help a theoretical problem? Which tree is it against? 'free_vmap_cache' doesn't show up in Linus's tree. > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d8e877365f9f..2638a20d36ce 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -441,7 +441,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > if (!free_vmap_cache || > size < cached_hole_size || > vstart < cached_vstart || > - align < cached_align) { > + align < cached_align || purged) { > nocache: > cached_hole_size = 0; > free_vmap_cache = NULL; Is 'purged' the right way to do this? There is a path through the overflow code that also sets purged=0. Does 'free_vmap_cache' *not* need to get reset in that case? It also seems more natural to me that the code mucking with the rbtree would be the one to reset the cache.
>On 4/12/20 7:38 AM, Liu Song wrote: >> If overflow, should ensure that "free_vmap_cache" is set to NULL, >> so as to ensure that it can be traversed from the beginning. > >This changelog is a bit sparse. > >Does this fix a demonstrated problem? Or was it just discovered via >code review and assumed to help a theoretical problem? > >Which tree is it against? 'free_vmap_cache' doesn't show up in Linus's >tree. >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index d8e877365f9f..2638a20d36ce 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -441,7 +441,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, >> if (!free_vmap_cache || >> size < cached_hole_size || >> vstart < cached_vstart || >> - align < cached_align) { >> + align < cached_align || purged) { >> nocache: >> cached_hole_size = 0; >> free_vmap_cache = NULL; > >Is 'purged' the right way to do this? > >There is a path through the overflow code that also sets purged=0. Does >'free_vmap_cache' *not* need to get reset in that case? > >It also seems more natural to me that the code mucking with the rbtree >would be the one to reset the cache. Hi, Thanks for your reply, there is indeed a problem with this patch submission. I neglected the cache clearing process, so I mistakenly thought that the cache should be cleared after "purged". I will not issue such unconsidered patches anymore, to avoid unnecessary trouble for everyone. *_^ Thanks
On Mon, Apr 13, 2020 at 08:02:49AM -0700, Dave Hansen wrote: > On 4/12/20 7:38 AM, Liu Song wrote: > > If overflow, should ensure that "free_vmap_cache" is set to NULL, > > so as to ensure that it can be traversed from the beginning. > > This changelog is a bit sparse. > > Does this fix a demonstrated problem? Or was it just discovered via > code review and assumed to help a theoretical problem? > > Which tree is it against? 'free_vmap_cache' doesn't show up in Linus's > tree. > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index d8e877365f9f..2638a20d36ce 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -441,7 +441,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > if (!free_vmap_cache || > > size < cached_hole_size || > > vstart < cached_vstart || > > - align < cached_align) { > > + align < cached_align || purged) { > > nocache: > > cached_hole_size = 0; > > free_vmap_cache = NULL; > > We do not have such code since 5.2 kernel or so, nor things like cached_hole_size, free_vmap_cache and so on. It was totally reworked. -- Vlad Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d8e877365f9f..2638a20d36ce 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -441,7 +441,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, if (!free_vmap_cache || size < cached_hole_size || vstart < cached_vstart || - align < cached_align) { + align < cached_align || purged) { nocache: cached_hole_size = 0; free_vmap_cache = NULL;