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Subject[PATCH v2 2/3] mm: separate memory allocation and actual work in alloc_vmap_area()
Date
alloc_vmap_area() is allocating memory for the vmap_area, and
performing the actual lookup of the vm area and vmap_area
initialization.

This prevents us from using a pre-allocated memory for the map_area
structure, which can be used in some cases to minimize the number
of required memory allocations.

Let's keep the memory allocation part in alloc_vmap_area() and
separate everything else into init_vmap_area().

Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
---
mm/vmalloc.c | 50 +++++++++++++++++++++++++++++++++-----------------
1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8f0179895fb5..f1f19d1105c4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -395,16 +395,10 @@ 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.
- */
-static struct vmap_area *alloc_vmap_area(unsigned long size,
- unsigned long align,
- unsigned long vstart, unsigned long vend,
- int node, gfp_t gfp_mask)
+static int init_vmap_area(struct vmap_area *va, unsigned long size,
+ unsigned long align, unsigned long vstart,
+ unsigned long vend, int node, gfp_t gfp_mask)
{
- struct vmap_area *va;
struct rb_node *n;
unsigned long addr;
int purged = 0;
@@ -416,11 +410,6 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,

might_sleep();

- va = kmalloc_node(sizeof(struct vmap_area),
- gfp_mask & GFP_RECLAIM_MASK, node);
- if (unlikely(!va))
- return ERR_PTR(-ENOMEM);
-
/*
* Only scan the relevant parts containing pointers to other objects
* to avoid false negatives.
@@ -516,7 +505,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
BUG_ON(va->va_start < vstart);
BUG_ON(va->va_end > vend);

- return va;
+ return 0;

overflow:
spin_unlock(&vmap_area_lock);
@@ -538,8 +527,35 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
pr_warn("vmap allocation for size %lu failed: use vmalloc=<size> to increase size\n",
size);
- kfree(va);
- return ERR_PTR(-EBUSY);
+
+ return -EBUSY;
+}
+
+/*
+ * Allocate a region of KVA of the specified size and alignment, within the
+ * vstart and vend.
+ */
+static struct vmap_area *alloc_vmap_area(unsigned long size,
+ unsigned long align,
+ unsigned long vstart,
+ unsigned long vend,
+ int node, gfp_t gfp_mask)
+{
+ struct vmap_area *va;
+ int ret;
+
+ va = kmalloc_node(sizeof(struct vmap_area),
+ gfp_mask & GFP_RECLAIM_MASK, node);
+ if (unlikely(!va))
+ return ERR_PTR(-ENOMEM);
+
+ ret = init_vmap_area(va, size, align, vstart, vend, node, gfp_mask);
+ if (ret) {
+ kfree(va);
+ return ERR_PTR(ret);
+ }
+
+ return va;
}

int register_vmap_purge_notifier(struct notifier_block *nb)
--
2.20.1
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