Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-10 22:21:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

hugetlb: fix huge_pmd_unshare address update

Browse Source 
The routine huge_pmd_unshare() is passed a pointer to an address
associated with an area which may be unshared.  If unshare is successful
this address is updated to 'optimize' callers iterating over huge page
addresses.  For the optimization to work correctly, address should be
updated to the last huge page in the unmapped/unshared area.  However, in
the common case where the passed address is PUD_SIZE aligned, the address
is incorrectly updated to the address of the preceding huge page.  That
wastes CPU cycles as the unmapped/unshared range is scanned twice.

Link: https://lkml.kernel.org/r/20220524205003.126184-1-mike.kravetz@oracle.com
Fixes: 39dde65c99 ("shared page table for hugetlb page")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Mike Kravetz 2022-05-24 13:50:03 -07:00 committed by akpm
parent 2505a98111
commit 48381273f8
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
mm/hugetlb.c
View File

@ -6562,7 +6562,14 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
pud_clear(pud);
put_page(virt_to_page(ptep));
mm_dec_nr_pmds(mm);
*addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
/*
* This update of passed address optimizes loops sequentially
* processing addresses in increments of huge page size (PMD_SIZE
* in this case). By clearing the pud, a PUD_SIZE area is unmapped.
* Update address to the 'last page' in the cleared area so that
* calling loop can move to first page past this area.
*/
*addr |= PUD_SIZE - PMD_SIZE;
return 1;
}