diff options
| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2023-06-29 20:14:14 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-07-01 08:10:56 -0700 |
| commit | e4bd84c069f212c01258e405f86e91f327888e41 (patch) | |
| tree | e58441bf268ac1b4e915567afb01b50f6103bc28 /mm/mmap.c | |
| parent | 03f889378f33aa9a9d8e5f49ba94134cf6158090 (diff) | |
mm: Always downgrade mmap_lock if requested
Now that stack growth must always hold the mmap_lock for write, we can
always downgrade the mmap_lock to read and safely unmap pages from the
page table, even if we're next to a stack.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 15 |
1 files changed, 2 insertions, 13 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 3e5793ebbaae..141c618847ac 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2551,19 +2551,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, /* Point of no return */ mm->locked_vm -= locked_vm; mm->map_count -= count; - /* - * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or - * VM_GROWSUP VMA. Such VMAs can change their size under - * down_read(mmap_lock) and collide with the VMA we are about to unmap. - */ - if (downgrade) { - if (next && (next->vm_flags & VM_GROWSDOWN)) - downgrade = false; - else if (prev && (prev->vm_flags & VM_GROWSUP)) - downgrade = false; - else - mmap_write_downgrade(mm); - } + if (downgrade) + mmap_write_downgrade(mm); /* * We can free page tables without write-locking mmap_lock because VMAs |