A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-29 03:01:39 -04:00
Code Issues Projects Releases Packages Wiki Activity

hugetlb: detect race upon page allocation failure during COW

Browse source 
Currently we are not rechecking pte_same in hugetlb_cow after we take ptl
lock again in the page allocation failure code path and simply retry
again.  This is not an issue at the moment because hugetlb fault path is
protected by hugetlb_instantiation_mutex so we cannot race.

The original page is locked and so we cannot race even with the page
migration.

Let's add the pte_same check anyway as we want to be consistent with the
other check later in this function and be safe if we ever remove the
mutex.

[[email protected]: reworded the changelog]
Signed-off-by: Hillf Danton <[email protected]>
Signed-off-by: Michal Hocko <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Hillf Danton 2012-01-10 15:07:20 -08:00 • committed by Linus Torvalds
commit a734bcc812
1 changed files with 8 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

9
mm/hugetlb.c
View file

@ -2408,7 +2408,14 @@ retry_avoidcopy:
BUG_ON(page_count(old_page) != 1);
BUG_ON(huge_pte_none(pte));
spin_lock(&mm->page_table_lock);
goto retry_avoidcopy;
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte)))
goto retry_avoidcopy;
/*
* race occurs while re-acquiring page_table_lock, and
* our job is done.
*/
return 0;
}
WARN_ON_ONCE(1);
}