Re: [RFC PATCH 1/5] mm/vmalloc.c: correct a few logic error for __insert_vmap_area()
From: zijun_hu <hidden>
Date: 2016-09-22 01:36:15
Also in:
lkml
On 09/21/2016 12:23 PM, zijun_hu wrote:
From: zijun_hu <redacted> correct a few logic error for __insert_vmap_area() since the else if condition is always true and meaningless in order to fix this issue, if vmap_area inserted is lower than one on rbtree then walk around left branch; if higher then right branch otherwise intersects with the other then BUG_ON() is triggered Signed-off-by: zijun_hu <redacted>
i give more explanation to the intent of my change any comments is welcome
quoted hunk ↗ jump to hunk
--- mm/vmalloc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 91f44e7..cc6ecd6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c@@ -321,10 +321,10 @@ static void __insert_vmap_area(struct vmap_area *va) parent = *p; tmp_va = rb_entry(parent, struct vmap_area, rb_node); - if (va->va_start < tmp_va->va_end) - p = &(*p)->rb_left; - else if (va->va_end > tmp_va->va_start) - p = &(*p)->rb_right;
this else if condition is always true and meaningless as long as there are no zero sized vamp_area due to the following expression va->va_end > va->va_start >= tmp_va->va_end > tmp_va->va_start
+ if (va->va_end <= tmp_va->va_start) + p = &parent->rb_left;
if the vamp_area to be inserted is lower than that on the rbtree then we walk around the left branch of the node given consider va->va_end == tmp_va->va_start as legal case which represent two neighbor areas tightly BTW, the available range of a vmap area include the start boundary not the end, namely, [start, end)
+ else if (va->va_start >= tmp_va->va_end) + p = &parent->rb_right;
if the vamp_area to be inserted is higher than that on the rbtree then we walk around the right branch of the node given
else BUG();
this indicate the vamp_area to be inserted have intersects with that on the rbtree then we remain the BUG() logic
}
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