On 2016/9/22 6:45, David Rientjes wrote: > On Thu, 22 Sep 2016, zijun_hu wrote: > >>>> 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 >>>> >>> >>> Under normal operation, you're right that the "else if" conditional should >>> always succeed: we don't want to BUG() unless there's a bug. The original >>> code can catch instances when va->va_start == tmp_va->va_end where we >>> should BUG(). Your code silently ignores it. >>> >> Hmm, the BUG_ON() appears in the original code, i don't introduce it. >> it maybe be better to consider va->va_start == tmp_va->va_end as normal case >> and should not BUG_ON() it since the available range of vmap_erea include >> the start boundary but the end, BTW, represented as [start, end) >> > > We don't support inserting when va->va_start == tmp_va->va_end, plain and > simple. There's no reason to do so. NACK to the patch. > i am sorry i disagree with you because 1) in almost all context of vmalloc, original logic treat the special case as normal for example, __find_vmap_area() or alloc_vmap_area() 2) don't use the limited vmap area effectively, it maybe causes BUG_ON() easy 3) consider below case it provided there have been two vmap_areas [4, 12) and [20, 28), what will happens when alloc_vmap_area(8, 4, 6, 24,...)? should we use [12,20) for our request? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>