Commit 46c043ed authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

mm: take i_mmap_lock in unmap_mapping_range() for DAX 



DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.

__dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
all mappings.  We need to drop i_mmap_lock there to avoid lock deadlock.

Re-aquiring the lock should be fine since we check i_size after the
point.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3fdd1b47

fs/dax.c

+19 −16
Original line number Diff line number Diff line
@@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, 
	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)

		goto fallback;



	if (buffer_unwritten(&bh) || buffer_new(&bh)) {

		int i;

		for (i = 0; i < PTRS_PER_PMD; i++)

			clear_page(kaddr + i * PAGE_SIZE);

		count_vm_event(PGMAJFAULT);

		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);

		result |= VM_FAULT_MAJOR;

	}



	/*

	 * If we allocated new storage, make sure no process has any

	 * zero pages covering this hole

	 */

	if (buffer_new(&bh)) {

		i_mmap_unlock_write(mapping);

		unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);

		i_mmap_lock_write(mapping);

	}



	/*

	 * If a truncate happened while we were allocating blocks, we may

	 * leave blocks allocated to the file that are beyond EOF.  We can't
@@ -568,13 +587,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, 
	if ((pgoff | PG_PMD_COLOUR) >= size)

		goto fallback;



	/*

	 * If we allocated new storage, make sure no process has any

	 * zero pages covering this hole

	 */

	if (buffer_new(&bh))

		unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);



	if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {

		spinlock_t *ptl;

		pmd_t entry;
@@ -605,15 +617,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, 
		if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))

			goto fallback;



		if (buffer_unwritten(&bh) || buffer_new(&bh)) {

			int i;

			for (i = 0; i < PTRS_PER_PMD; i++)

				clear_page(kaddr + i * PAGE_SIZE);

			count_vm_event(PGMAJFAULT);

			mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);

			result |= VM_FAULT_MAJOR;

		}



		result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);

	}

mm/memory.c

+2 −9
Original line number Diff line number Diff line
@@ -2426,16 +2426,9 @@ void unmap_mapping_range(struct address_space *mapping, 
	if (details.last_index < details.first_index)

		details.last_index = ULONG_MAX;





	/*

	 * DAX already holds i_mmap_lock to serialise file truncate vs

	 * page fault and page fault vs page fault.

	 */

	if (!IS_DAX(mapping->host))

	i_mmap_lock_write(mapping);

	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))

		unmap_mapping_range_tree(&mapping->i_mmap, &details);

	if (!IS_DAX(mapping->host))

	i_mmap_unlock_write(mapping);

}

EXPORT_SYMBOL(unmap_mapping_range);

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