diff options
Diffstat (limited to 'arch/s390/mm/vmem.c')
| -rw-r--r-- | arch/s390/mm/vmem.c | 51 |
1 files changed, 50 insertions, 1 deletions
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c index e82a63de19db..df361bbacda1 100644 --- a/arch/s390/mm/vmem.c +++ b/arch/s390/mm/vmem.c @@ -72,6 +72,42 @@ static void vmem_pte_free(unsigned long *table) page_table_free(&init_mm, table); } +#define PAGE_UNUSED 0xFD + +static void vmemmap_use_sub_pmd(unsigned long start, unsigned long end) +{ + /* + * As we expect to add in the same granularity as we remove, it's + * sufficient to mark only some piece used to block the memmap page from + * getting removed (just in case the memmap never gets initialized, + * e.g., because the memory block never gets onlined). + */ + memset(__va(start), 0, sizeof(struct page)); +} + +static void vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end) +{ + void *page = __va(ALIGN_DOWN(start, PMD_SIZE)); + + /* Could be our memmap page is filled with PAGE_UNUSED already ... */ + vmemmap_use_sub_pmd(start, end); + + /* Mark the unused parts of the new memmap page PAGE_UNUSED. */ + if (!IS_ALIGNED(start, PMD_SIZE)) + memset(page, PAGE_UNUSED, start - __pa(page)); + if (!IS_ALIGNED(end, PMD_SIZE)) + memset(__va(end), PAGE_UNUSED, __pa(page) + PMD_SIZE - end); +} + +/* Returns true if the PMD is completely unused and can be freed. */ +static bool vmemmap_unuse_sub_pmd(unsigned long start, unsigned long end) +{ + void *page = __va(ALIGN_DOWN(start, PMD_SIZE)); + + memset(__va(start), PAGE_UNUSED, end - start); + return !memchr_inv(page, PAGE_UNUSED, PMD_SIZE); +} + /* __ref: we'll only call vmemmap_alloc_block() via vmemmap_populate() */ static int __ref modify_pte_table(pmd_t *pmd, unsigned long addr, unsigned long end, bool add, bool direct) @@ -157,6 +193,11 @@ static int __ref modify_pmd_table(pud_t *pud, unsigned long addr, get_order(PMD_SIZE)); pmd_clear(pmd); pages++; + } else if (!direct && + vmemmap_unuse_sub_pmd(addr, next)) { + vmem_free_pages(pmd_deref(*pmd), + get_order(PMD_SIZE)); + pmd_clear(pmd); } continue; } @@ -182,6 +223,11 @@ static int __ref modify_pmd_table(pud_t *pud, unsigned long addr, NUMA_NO_NODE); if (new_page) { pmd_val(*pmd) = __pa(new_page) | prot; + if (!IS_ALIGNED(addr, PMD_SIZE) || + !IS_ALIGNED(next, PMD_SIZE)) { + vmemmap_use_new_sub_pmd(addr, + next); + } continue; } } @@ -189,8 +235,11 @@ static int __ref modify_pmd_table(pud_t *pud, unsigned long addr, if (!pte) goto out; pmd_populate(&init_mm, pmd, pte); - } else if (pmd_large(*pmd)) + } else if (pmd_large(*pmd)) { + if (!direct) + vmemmap_use_sub_pmd(addr, next); continue; + } ret = modify_pte_table(pmd, addr, next, add, direct); if (ret) |