Hi, Chris. Comment is below.
On Thu, Mar 17, 2016 at 12:59 PM, Chris Wilson <ch...@chris-wilson.co.uk> wrote: > vmaps are temporary kernel mappings that may be of long duration. > Reusing a vmap on an object is preferrable for a driver as the cost of > setting up the vmap can otherwise dominate the operation on the object. > However, the vmap address space is rather limited on 32bit systems and > so we add a notification for vmap pressure in order for the driver to > release any cached vmappings. > > The interface is styled after the oom-notifier where the callees are > passed a pointer to an unsigned long counter for them to indicate if they > have freed any space. > > Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: David Rientjes <rient...@google.com> > Cc: Roman Pen <r.peni...@gmail.com> > Cc: Mel Gorman <mgor...@techsingularity.net> > Cc: linux...@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > include/linux/vmalloc.h | 4 ++++ > mm/vmalloc.c | 22 ++++++++++++++++++++++ > 2 files changed, 26 insertions(+) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index d1f1d338af20..edd676b8e112 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -187,4 +187,8 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms) > #define VMALLOC_TOTAL 0UL > #endif > > +struct notitifer_block; > +int register_vmap_purge_notifier(struct notifier_block *nb); > +int unregister_vmap_purge_notifier(struct notifier_block *nb); > + > #endif /* _LINUX_VMALLOC_H */ > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index fb42a5bffe47..fd2ca94c2732 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -21,6 +21,7 @@ > #include <linux/debugobjects.h> > #include <linux/kallsyms.h> > #include <linux/list.h> > +#include <linux/notifier.h> > #include <linux/rbtree.h> > #include <linux/radix-tree.h> > #include <linux/rcupdate.h> > @@ -344,6 +345,8 @@ static void __insert_vmap_area(struct vmap_area *va) > > static void purge_vmap_area_lazy(void); > > +static BLOCKING_NOTIFIER_HEAD(vmap_notify_list); > + > /* > * Allocate a region of KVA of the specified size and alignment, within the > * vstart and vend. > @@ -356,6 +359,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long > size, > struct vmap_area *va; > struct rb_node *n; > unsigned long addr; > + unsigned long freed; > int purged = 0; > struct vmap_area *first; > > @@ -468,6 +472,12 @@ overflow: > purged = 1; > goto retry; > } > + freed = 0; > + blocking_notifier_call_chain(&vmap_notify_list, 0, &freed); It seems to me that alloc_vmap_area() was designed not to sleep, at least on GFP_NOWAIT path (__GFP_DIRECT_RECLAIM is not set). But blocking_notifier_call_chain() might sleep. Roman.
