When freeing vmalloc range mapping, only unmapping the page tables is done, TLB flush is lazily deferred to a late stage until lazy_max_pages() is met or vmalloc() can't find available virtual memory region. However, to free VM_FLUSH_RESET_PERMS memory of vmalloc, TLB flushing need be done immediately before freeing pages, and the direct map needs resetting permissions and TLB flushing. Please see commit 868b104d7379 ("mm/vmalloc: Add flag for freeing of special permsissions") for more details. In the current code, when freeing VM_FLUSH_RESET_PERMS memory, lazy purge is also done to try to save a TLB flush later. When doing that, it merges the direct map range with the percpu vbq dirty range and all purge ranges by calculating flush range of [min:max]. That will add the huge gap between direct map range and vmalloc range into the final TLB flush range. So here, only flush VM_FLUSH_RESET_PERMS area immediately, and leave the lazy flush to the normal points, e.g when allocating a new vmap_area, or lazy_max_pages() is met. Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> --- mm/vmalloc.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 31e8d9e93650..87134dd8abc3 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2690,9 +2690,10 @@ static inline void set_area_direct_map(const struct vm_struct *area, */ static void vm_reset_perms(struct vm_struct *area) { - unsigned long start = ULONG_MAX, end = 0; + unsigned long start = ULONG_MAX, end = 0, pages = 0; unsigned int page_order = vm_area_page_order(area); - int flush_dmap = 0; + struct list_head local_flush_list; + struct vmap_area alias_va, va; int i; /* @@ -2708,17 +2709,33 @@ static void vm_reset_perms(struct vm_struct *area) page_size = PAGE_SIZE << page_order; start = min(addr, start); end = max(addr + page_size, end); - flush_dmap = 1; } } + va.va_start = (unsigned long)area->addr; + va.va_end = (unsigned long)(area->addr + area->size); /* * Set direct map to something invalid so that it won't be cached if * there are any accesses after the TLB flush, then flush the TLB and * reset the direct map permissions to the default. */ set_area_direct_map(area, set_direct_map_invalid_noflush); - _vm_unmap_aliases(start, end, flush_dmap); + if (IS_ENABLED(CONFIG_HAVE_FLUSH_TLB_KERNEL_VAS)) { + if (end > start) { + pages = (end - start) >> PAGE_SHIFT; + alias_va.va_start = (unsigned long)start; + alias_va.va_end = (unsigned long)end; + list_add(&alias_va.list, &local_flush_list); + } + + pages += area->size >> PAGE_SHIFT; + list_add(&va.list, &local_flush_list); + + flush_tlb_kernel_vas(&local_flush_list, pages); + } else { + flush_tlb_kernel_range(start, end); + flush_tlb_kernel_range(va.va_start, va.va_end); + } set_area_direct_map(area, set_direct_map_default_noflush); } -- 2.34.1