Commit 1d069b7d authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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huge pagecache: extend mremap pmd rmap lockout to files 



Whatever huge pagecache implementation we go with, file rmap locking
must be added to anon rmap locking, when mremap's move_page_tables()
finds a pmd_trans_huge pmd entry: a simple change, let's do it now.

Factor out take_rmap_locks() and drop_rmap_locks() to handle the locking
for make move_ptes() and move_page_tables(), and delete the
VM_BUG_ON_VMA which rejected vm_file and required anon_vma.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Ning Qu <quning@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bf8616d5

mm/mremap.c

+22 −20
Original line number Diff line number Diff line
@@ -70,6 +70,22 @@ static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, 
	return pmd;

}



static void take_rmap_locks(struct vm_area_struct *vma)

{

	if (vma->vm_file)

		i_mmap_lock_write(vma->vm_file->f_mapping);

	if (vma->anon_vma)

		anon_vma_lock_write(vma->anon_vma);

}



static void drop_rmap_locks(struct vm_area_struct *vma)

{

	if (vma->anon_vma)

		anon_vma_unlock_write(vma->anon_vma);

	if (vma->vm_file)

		i_mmap_unlock_write(vma->vm_file->f_mapping);

}



static pte_t move_soft_dirty_pte(pte_t pte)

{

	/*
@@ -90,8 +106,6 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 
		struct vm_area_struct *new_vma, pmd_t *new_pmd,

		unsigned long new_addr, bool need_rmap_locks)

{

	struct address_space *mapping = NULL;

	struct anon_vma *anon_vma = NULL;

	struct mm_struct *mm = vma->vm_mm;

	pte_t *old_pte, *new_pte, pte;

	spinlock_t *old_ptl, *new_ptl;
@@ -114,16 +128,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 
	 *   serialize access to individual ptes, but only rmap traversal

	 *   order guarantees that we won't miss both the old and new ptes).

	 */

	if (need_rmap_locks) {

		if (vma->vm_file) {

			mapping = vma->vm_file->f_mapping;

			i_mmap_lock_write(mapping);

		}

		if (vma->anon_vma) {

			anon_vma = vma->anon_vma;

			anon_vma_lock_write(anon_vma);

		}

	}

	if (need_rmap_locks)

		take_rmap_locks(vma);



	/*

	 * We don't have to worry about the ordering of src and dst
@@ -151,10 +157,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 
		spin_unlock(new_ptl);

	pte_unmap(new_pte - 1);

	pte_unmap_unlock(old_pte - 1, old_ptl);

	if (anon_vma)

		anon_vma_unlock_write(anon_vma);

	if (mapping)

		i_mmap_unlock_write(mapping);

	if (need_rmap_locks)

		drop_rmap_locks(vma);

}



#define LATENCY_LIMIT	(64 * PAGE_SIZE)
@@ -193,15 +197,13 @@ unsigned long move_page_tables(struct vm_area_struct *vma, 
		if (pmd_trans_huge(*old_pmd)) {

			if (extent == HPAGE_PMD_SIZE) {

				bool moved;

				VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,

					      vma);

				/* See comment in move_ptes() */

				if (need_rmap_locks)

					anon_vma_lock_write(vma->anon_vma);

					take_rmap_locks(vma);

				moved = move_huge_pmd(vma, old_addr, new_addr,

						    old_end, old_pmd, new_pmd);

				if (need_rmap_locks)

					anon_vma_unlock_write(vma->anon_vma);

					drop_rmap_locks(vma);

				if (moved) {

					need_flush = true;

					continue;

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