Commit be48be9e authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Liu Shixin
Browse files

mm: assert the mmap_lock is held in __anon_vma_prepare() 

mainline inclusion
from mainline-v6.10-rc1
commit 3be51060599ff01899b6d8c3f8aca456506cf5ea
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9R3AY
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3be51060599ff01899b6d8c3f8aca456506cf5ea

--------------------------------

Patch series "Improve anon_vma scalability for anon VMAs".

We have a 3x throughput improvement reported by Intel's kernel test robot:
https://lore.kernel.org/all/202404261055.c5e24608-oliver.sang@intel.com/

This is from delaying taking the mmap_lock for page faults until we
actually need the mmap_lock in order to assign an anon_vma to the vma.  It
cleans up the page fault path a little by making the anon fault handler
more similar to the file fault handler.

This patch (of 4):

Convert the comment into an assertion.

Link: https://lkml.kernel.org/r/20240426144506.1290619-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240426144506.1290619-2-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 97824705

mm/rmap.c

+1 −2
Original line number Diff line number Diff line
@@ -182,8 +182,6 @@ static void anon_vma_chain_link(struct vm_area_struct *vma, 
 * for the new allocation. At the same time, we do not want

 * to do any locking for the common case of already having

 * an anon_vma.

 *

 * This must be called with the mmap_lock held for reading.

 */

int __anon_vma_prepare(struct vm_area_struct *vma)

{
@@ -191,6 +189,7 @@ int __anon_vma_prepare(struct vm_area_struct *vma) 
	struct anon_vma *anon_vma, *allocated;

	struct anon_vma_chain *avc;



	mmap_assert_locked(mm);

	might_sleep();



	avc = anon_vma_chain_alloc(GFP_KERNEL);