Commit 2a058ab3 authored by Vishal Moola (Oracle)'s avatar Vishal Moola (Oracle) Committed by Andrew Morton
Browse files

mm: change vmf_anon_prepare() to __vmf_anon_prepare() 

Some callers of vmf_anon_prepare() may not want us to release the per-VMA
lock ourselves.  Rename vmf_anon_prepare() to __vmf_anon_prepare() and let
the callers drop the lock when desired.

Also, make vmf_anon_prepare() a wrapper that releases the per-VMA lock
itself for any callers that don't care.

This is in preparation to fix this bug reported by syzbot:
https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.com/

Link: https://lkml.kernel.org/r/20240914194243.245-1-vishal.moola@gmail.com


Fixes: 9acad7ba ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()")
Reported-by: default avatar <syzbot+2dab93857ee95f2eeb08@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.com/


Signed-off-by: default avatarVishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b4afe418

mm/internal.h

+10 −1
Original line number Diff line number Diff line
@@ -310,7 +310,16 @@ static inline void wake_throttle_isolated(pg_data_t *pgdat) 
		wake_up(wqh);

}



vm_fault_t vmf_anon_prepare(struct vm_fault *vmf);

vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf);

static inline vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)

{

	vm_fault_t ret = __vmf_anon_prepare(vmf);



	if (unlikely(ret & VM_FAULT_RETRY))

		vma_end_read(vmf->vma);

	return ret;

}



vm_fault_t do_swap_page(struct vm_fault *vmf);

void folio_rotate_reclaimable(struct folio *folio);

bool __folio_end_writeback(struct folio *folio);

mm/memory.c

+3 −5
Original line number Diff line number Diff line
@@ -3259,7 +3259,7 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf) 
}



/**

 * vmf_anon_prepare - Prepare to handle an anonymous fault.

 * __vmf_anon_prepare - Prepare to handle an anonymous fault.

 * @vmf: The vm_fault descriptor passed from the fault handler.

 *

 * When preparing to insert an anonymous page into a VMA from a
@@ -3273,7 +3273,7 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf) 
 * Return: 0 if fault handling can proceed.  Any other value should be

 * returned to the caller.

 */

vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)

vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf)

{

	struct vm_area_struct *vma = vmf->vma;

	vm_fault_t ret = 0;
@@ -3281,11 +3281,9 @@ vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) 
	if (likely(vma->anon_vma))

		return 0;

	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {

		if (!mmap_read_trylock(vma->vm_mm)) {

			vma_end_read(vma);

		if (!mmap_read_trylock(vma->vm_mm))

			return VM_FAULT_RETRY;

	}

	}

	if (__anon_vma_prepare(vma))

		ret = VM_FAULT_OOM;

	if (vmf->flags & FAULT_FLAG_VMA_LOCK)