Re: [PATCH v4 2/3] drm/i915: refactor duplicate object vmap functions (reworked)

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

On Tue, Feb 23, 2016 at 11:38:02AM +0000, Chris Wilson wrote:
> Indeed, we would need a new notifier, pretty much for the sole use of
> 32b. Grr, that will be a nuisance.

Core changes:

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index d1f1d338af20..542a91c2785f 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_notifier(struct notifier_block *nb);
+int unregister_vmap_notifier(struct notifier_block *nb);
+
 #endif /* _LINUX_VMALLOC_H */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fb42a5bffe47..0735d82444f7 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);
+       if (freed > 0) {
+               purged = 0;
+               goto retry;
+       }
        if (printk_ratelimit())
                pr_warn("vmap allocation for size %lu failed: "
                        "use vmalloc=<size> to increase size.\n", size);
@@ -475,6 +485,18 @@ overflow:
        return ERR_PTR(-EBUSY);
 }
 
+int register_vmap_notifier(struct notifier_block *nb)
+{
+       return blocking_notifier_chain_register(&vmap_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_vmap_notifier);
+
+int unregister_vmap_notifier(struct notifier_block *nb)
+{
+       return blocking_notifier_chain_unregister(&vmap_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_vmap_notifier);
+
 static void __free_vmap_area(struct vmap_area *va)
 {
        BUG_ON(RB_EMPTY_NODE(&va->rb_node));


That doesn't look too horrendous. Names?

register_oovmap_notifier
register_vmap_nospace_notifier?
register_vmap_purge_notifier?

And the 64k question, how to sell it?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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