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authorMatthew Wilcox (Oracle) <willy@infradead.org>2023-06-29 20:14:14 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2023-07-01 08:10:56 -0700
commite4bd84c069f212c01258e405f86e91f327888e41 (patch)
treee58441bf268ac1b4e915567afb01b50f6103bc28 /mm
parent03f889378f33aa9a9d8e5f49ba94134cf6158090 (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')
-rw-r--r--mm/mmap.c15
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