On Thu, 2018-03-15 at 13:09 +0530, Chintan Pandya wrote:
On 3/14/2018 11:31 PM, Toshi Kani wrote:
Implement pud_free_pmd_page() and pmd_free_pte_page() on x86, which clear a given pud/pmd entry and free up lower level page table(s). Address range associated with the pud/pmd entry must have been purged by INVLPG.
fixes: e61ce6ade404e ("mm: change ioremap to set up huge I/O mappings") Signed-off-by: Toshi Kani toshi.kani@hpe.com Cc: Michal Hocko mhocko@suse.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Borislav Petkov bp@suse.de Cc: Matthew Wilcox willy@infradead.org Cc: stable@vger.kernel.org
arch/x86/mm/pgtable.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 1eed7ed518e6..34cda7e0551b 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -712,7 +712,22 @@ int pmd_clear_huge(pmd_t *pmd) */ int pud_free_pmd_page(pud_t *pud) {
- return pud_none(*pud);
- pmd_t *pmd;
- int i;
- if (pud_none(*pud))
return 1;- pmd = (pmd_t *)pud_page_vaddr(*pud);
- for (i = 0; i < PTRS_PER_PMD; i++)
if (!pmd_free_pte_page(&pmd[i]))This is forced action and no optional. Also, pmd_free_pte_page() doesn't return 0 in any case. So, you may remove _if_ ?
The code needs to be written per the interface definition, not per the current implementation.
return 0;- pud_clear(pud);
- free_page((unsigned long)pmd);
- return 1; }
/** @@ -724,6 +739,15 @@ int pud_free_pmd_page(pud_t *pud) */ int pmd_free_pte_page(pmd_t *pmd) {
- return pmd_none(*pmd);
- pte_t *pte;
- if (pmd_none(*pmd))
This should also check if pmd is already huge. Same for pud ?
Not necessary. As described in the function header, one of the entry conditions is that a given pmd range is unmapped. See vunmap_pmd_range().
Thanks, -Toshi