| Message ID | 20190708170631.2130-1-lpf.vector@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/vmalloc.c: Remove always-true conditional in vmap_init_free_space | expand |
On Tue, Jul 09, 2019 at 01:06:31AM +0800, Pengfei Li wrote: > When unsigned long variables are subtracted from one another, > the result is always non-negative. > > The vmap_area_list is sorted by address. > > So the following two conditions are always true. > > 1) if (busy->va_start - vmap_start > 0) > 2) if (vmap_end - vmap_start > 0) > > Just remove them. That condition won't be true if busy->va_start == vmap_start.
On Tue, Jul 9, 2019 at 1:35 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Tue, Jul 09, 2019 at 01:06:31AM +0800, Pengfei Li wrote: > > When unsigned long variables are subtracted from one another, > > the result is always non-negative. > > > > The vmap_area_list is sorted by address. > > > > So the following two conditions are always true. > > > > 1) if (busy->va_start - vmap_start > 0) > > 2) if (vmap_end - vmap_start > 0) > > > > Just remove them. > > That condition won't be true if busy->va_start == vmap_start. Yes, you're right. Sorry for my bad job.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 0f76cca32a1c..c7bdbdc18472 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1810,31 +1810,25 @@ static void vmap_init_free_space(void) * |<--------------------------------->| */ list_for_each_entry(busy, &vmap_area_list, list) { - if (busy->va_start - vmap_start > 0) { - free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT); - if (!WARN_ON_ONCE(!free)) { - free->va_start = vmap_start; - free->va_end = busy->va_start; - - insert_vmap_area_augment(free, NULL, - &free_vmap_area_root, - &free_vmap_area_list); - } - } - - vmap_start = busy->va_end; - } - - if (vmap_end - vmap_start > 0) { free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT); if (!WARN_ON_ONCE(!free)) { free->va_start = vmap_start; - free->va_end = vmap_end; + free->va_end = busy->va_start; insert_vmap_area_augment(free, NULL, - &free_vmap_area_root, - &free_vmap_area_list); + &free_vmap_area_root, &free_vmap_area_list); } + + vmap_start = busy->va_end; + } + + free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT); + if (!WARN_ON_ONCE(!free)) { + free->va_start = vmap_start; + free->va_end = vmap_end; + + insert_vmap_area_augment(free, NULL, + &free_vmap_area_root, &free_vmap_area_list); } }
When unsigned long variables are subtracted from one another, the result is always non-negative. The vmap_area_list is sorted by address. So the following two conditions are always true. 1) if (busy->va_start - vmap_start > 0) 2) if (vmap_end - vmap_start > 0) Just remove them. Signed-off-by: Pengfei Li <lpf.vector@gmail.com> --- mm/vmalloc.c | 32 +++++++++++++------------------- 1 file changed, 13 insertions(+), 19 deletions(-)