[lkml]   [2020]   [Sep]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2] page_alloc: Fix freeing non-compound pages
On Mon, Sep 28, 2020 at 06:03:07PM -0700, Andrew Morton wrote:
> Well that's weird and scary looking. `page' has non-zero refcount yet
> we go and free random followon pages. Methinks it merits an
> explanatory comment?

Here's some kernel-doc. Opinions?

* __free_pages - Free pages allocated with alloc_pages().
* @page: The page pointer returned from alloc_pages().
* @order: The order of the allocation.
* This function differs from put_page() in that it can free multi-page
* allocations that were not allocated with %__GFP_COMP. This function
* does not check that the @order passed in matches that of the
* allocation, so it is possible to leak memory. Freeing more memory than
* was allocated will probably be warned about by other debugging checks.
* It is only safe to use the page reference count to determine when
* to free an allocation if you use %__GFP_COMP (in which case, you may
* as well use put_page() to free the page). Another thread may have a
* speculative reference to the first page, but it has no way of knowing
* about the rest of the allocation, so we have to free all but the
* first page here.
* Context: May be called in interrupt context but not NMI context.

 \ /
  Last update: 2020-09-29 05:41    [W:0.064 / U:0.324 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site