| Message ID | 20170126103216.GG6590@dhcp22.suse.cz |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
On 01/26/2017 11:32 AM, Michal Hocko wrote: > On Thu 26-01-17 11:08:02, Michal Hocko wrote: >> On Thu 26-01-17 10:36:49, Daniel Borkmann wrote: >>> On 01/26/2017 08:43 AM, Michal Hocko wrote: >>>> On Wed 25-01-17 21:16:42, Daniel Borkmann wrote: >> [...] >>>>> I assume that kvzalloc() is still the same from [1], right? If so, then >>>>> it would unfortunately (partially) reintroduce the issue that was fixed. >>>>> If you look above at flags, they're also passed to __vmalloc() to not >>>>> trigger OOM in these situations I've experienced. >>>> >>>> Pushing __GFP_NORETRY to __vmalloc doesn't have the effect you might >>>> think it would. It can still trigger the OOM killer becauset the flags >>>> are no propagated all the way down to all allocations requests (e.g. >>>> page tables). This is the same reason why GFP_NOFS is not supported in >>>> vmalloc. >>> >>> Ok, good to know, is that somewhere clearly documented (like for the >>> case with kmalloc())? >> >> I am afraid that we really suck on this front. I will add something. > > So I have folded the following to the patch 1. It is in line with > kvmalloc and hopefully at least tell more than the current code. > --- > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d89034a393f2..6c1aa2c68887 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > * Allocate enough pages to cover @size from the page level > * allocator with @gfp_mask flags. Map them into contiguous > * kernel virtual space, using a pagetable protection of @prot. > + * > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > + * and __GFP_NOFAIL are not supported We could probably also mention that __GFP_ZERO in @gfp_mask is supported, though. > + * Any use of gfp flags outside of GFP_KERNEL should be consulted > + * with mm people. Just a question: should that read 'GFP_KERNEL | __GFP_HIGHMEM' as that is what vmalloc() resp. vzalloc() and others pass as flags? > + * > */ Sounds good otherwise, thanks Michal! > static void *__vmalloc_node(unsigned long size, unsigned long align, > gfp_t gfp_mask, pgprot_t prot,
On Thu 26-01-17 12:04:13, Daniel Borkmann wrote: > On 01/26/2017 11:32 AM, Michal Hocko wrote: > > On Thu 26-01-17 11:08:02, Michal Hocko wrote: > > > On Thu 26-01-17 10:36:49, Daniel Borkmann wrote: > > > > On 01/26/2017 08:43 AM, Michal Hocko wrote: > > > > > On Wed 25-01-17 21:16:42, Daniel Borkmann wrote: > > > [...] > > > > > > I assume that kvzalloc() is still the same from [1], right? If so, then > > > > > > it would unfortunately (partially) reintroduce the issue that was fixed. > > > > > > If you look above at flags, they're also passed to __vmalloc() to not > > > > > > trigger OOM in these situations I've experienced. > > > > > > > > > > Pushing __GFP_NORETRY to __vmalloc doesn't have the effect you might > > > > > think it would. It can still trigger the OOM killer becauset the flags > > > > > are no propagated all the way down to all allocations requests (e.g. > > > > > page tables). This is the same reason why GFP_NOFS is not supported in > > > > > vmalloc. > > > > > > > > Ok, good to know, is that somewhere clearly documented (like for the > > > > case with kmalloc())? > > > > > > I am afraid that we really suck on this front. I will add something. > > > > So I have folded the following to the patch 1. It is in line with > > kvmalloc and hopefully at least tell more than the current code. > > --- > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index d89034a393f2..6c1aa2c68887 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > > * Allocate enough pages to cover @size from the page level > > * allocator with @gfp_mask flags. Map them into contiguous > > * kernel virtual space, using a pagetable protection of @prot. > > + * > > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > > + * and __GFP_NOFAIL are not supported > > We could probably also mention that __GFP_ZERO in @gfp_mask is > supported, though. There are others which would be supported so I would rather stay with explicit unsupported. > > > + * Any use of gfp flags outside of GFP_KERNEL should be consulted > > + * with mm people. > > Just a question: should that read 'GFP_KERNEL | __GFP_HIGHMEM' as > that is what vmalloc() resp. vzalloc() and others pass as flags? yes, even though I think that specifying __GFP_HIGHMEM shouldn't be really necessary. Are there any users who would really insist on vmalloc pages in lowmem? Anyway this made me recheck kvmalloc_node implementation and I am not adding this flags which would mean a regression from the current state. Will fix it up.
On Thu, 2017-01-26 at 11:32 +0100, Michal Hocko wrote: > So I have folded the following to the patch 1. It is in line with > kvmalloc and hopefully at least tell more than the current code. [] > diff --git a/mm/vmalloc.c b/mm/vmalloc.c [] > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > * Allocate enough pages to cover @size from the page level > * allocator with @gfp_mask flags. Map them into contiguous > * kernel virtual space, using a pagetable protection of @prot. > + * > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > + * and __GFP_NOFAIL are not supported Maybe add a BUILD_BUG or a WARN_ON_ONCE to catch new occurrences?
On Thu 26-01-17 04:14:37, Joe Perches wrote: > On Thu, 2017-01-26 at 11:32 +0100, Michal Hocko wrote: > > So I have folded the following to the patch 1. It is in line with > > kvmalloc and hopefully at least tell more than the current code. > [] > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > [] > > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > > * Allocate enough pages to cover @size from the page level > > * allocator with @gfp_mask flags. Map them into contiguous > > * kernel virtual space, using a pagetable protection of @prot. > > + * > > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > > + * and __GFP_NOFAIL are not supported > > Maybe add a BUILD_BUG or a WARN_ON_ONCE to catch new occurrences? I would really like to not touch vmalloc in this series.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d89034a393f2..6c1aa2c68887 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, * Allocate enough pages to cover @size from the page level * allocator with @gfp_mask flags. Map them into contiguous * kernel virtual space, using a pagetable protection of @prot. + * + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT + * and __GFP_NOFAIL are not supported + * + * Any use of gfp flags outside of GFP_KERNEL should be consulted + * with mm people. + * */ static void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask, pgprot_t prot,