[PATCH v2 5/7] mm: Introduce may_mmap_overlapped_region() helper
From: Kirill Tkhai <hidden>
Date: 2019-05-20 14:00:59
Also in:
linux-mm, lkml
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
Extract address space limit check for overlapped regions in a separate helper. v2: New Signed-off-by: Kirill Tkhai <redacted> --- mm/mmap.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index e4ced5366643..260e47e917e6 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -583,6 +583,24 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm, return nr_pages; } +/* + * Check against address space limit, whether we may expand mm + * with a new mapping. Currently mapped in the given range pages + * are not accounted in the limit. + */ +static bool may_mmap_overlapped_region(struct mm_struct *mm, + unsigned long vm_flags, unsigned long addr, unsigned long len) +{ + unsigned long nr_pages = len >> PAGE_SHIFT; + + if (!may_expand_vm(mm, vm_flags, nr_pages)) { + nr_pages -= count_vma_pages_range(mm, addr, addr + len); + if (!may_expand_vm(mm, vm_flags, nr_pages)) + return false; + } + return true; +} + void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma, struct rb_node **rb_link, struct rb_node *rb_parent) {
@@ -1697,19 +1715,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long charged = 0; /* Check against address space limit. */ - if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) { - unsigned long nr_pages; - - /* - * MAP_FIXED may remove pages of mappings that intersects with - * requested mapping. Account for the pages it would unmap. - */ - nr_pages = count_vma_pages_range(mm, addr, addr + len); - - if (!may_expand_vm(mm, vm_flags, - (len >> PAGE_SHIFT) - nr_pages)) - return -ENOMEM; - } + if (!may_mmap_overlapped_region(mm, vm_flags, addr, len)) + return -ENOMEM; /* Clear old maps */ while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,