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Commit 53a7706d authored by Michel Lespinasse's avatar Michel Lespinasse Committed by Linus Torvalds
Browse files

mlock: do not hold mmap_sem for extended periods of time 



__get_user_pages gets a new 'nonblocking' parameter to signal that the
caller is prepared to re-acquire mmap_sem and retry the operation if
needed.  This is used to split off long operations if they are going to
block on a disk transfer, or when we detect contention on the mmap_sem.

[akpm@linux-foundation.org: remove ref to rwsem_is_contended()]
Signed-off-by: default avatarMichel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5fdb2002

mm/internal.h

+2 −1
Original line number Diff line number Diff line
@@ -243,7 +243,8 @@ static inline void mminit_validate_memmodel_limits(unsigned long *start_pfn, 


int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,

		     unsigned long start, int len, unsigned int foll_flags,

		     struct page **pages, struct vm_area_struct **vmas);

		     struct page **pages, struct vm_area_struct **vmas,

		     int *nonblocking);



#define ZONE_RECLAIM_NOSCAN	-2

#define ZONE_RECLAIM_FULL	-1

mm/memory.c

+18 −5
Original line number Diff line number Diff line
@@ -1363,7 +1363,8 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, 


int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,

		     unsigned long start, int nr_pages, unsigned int gup_flags,

		     struct page **pages, struct vm_area_struct **vmas)

		     struct page **pages, struct vm_area_struct **vmas,

		     int *nonblocking)

{

	int i;

	unsigned long vm_flags;
@@ -1463,10 +1464,15 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
			cond_resched();

			while (!(page = follow_page(vma, start, foll_flags))) {

				int ret;

				unsigned int fault_flags = 0;



				if (foll_flags & FOLL_WRITE)

					fault_flags |= FAULT_FLAG_WRITE;

				if (nonblocking)

					fault_flags |= FAULT_FLAG_ALLOW_RETRY;



				ret = handle_mm_fault(mm, vma, start,

					(foll_flags & FOLL_WRITE) ?

					FAULT_FLAG_WRITE : 0);

							fault_flags);



				if (ret & VM_FAULT_ERROR) {

					if (ret & VM_FAULT_OOM)
@@ -1482,6 +1488,11 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
				else

					tsk->min_flt++;



				if (ret & VM_FAULT_RETRY) {

					*nonblocking = 0;

					return i;

				}



				/*

				 * The VM_FAULT_WRITE bit tells us that

				 * do_wp_page has broken COW when necessary,
@@ -1581,7 +1592,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
	if (force)

		flags |= FOLL_FORCE;



	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);

	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,

				NULL);

}

EXPORT_SYMBOL(get_user_pages);
@@ -1606,7 +1618,8 @@ struct page *get_dump_page(unsigned long addr) 
	struct page *page;



	if (__get_user_pages(current, current->mm, addr, 1,

			FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)

			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,

			     NULL) < 1)

		return NULL;

	flush_cache_page(vma, addr, page_to_pfn(page));

	return page;

mm/mlock.c

+23 −17
Original line number Diff line number Diff line
@@ -155,13 +155,13 @@ static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long add 
 * vma->vm_mm->mmap_sem must be held for at least read.

 */

static long __mlock_vma_pages_range(struct vm_area_struct *vma,

				    unsigned long start, unsigned long end)

				    unsigned long start, unsigned long end,

				    int *nonblocking)

{

	struct mm_struct *mm = vma->vm_mm;

	unsigned long addr = start;

	int nr_pages = (end - start) / PAGE_SIZE;

	int gup_flags;

	int ret;



	VM_BUG_ON(start & ~PAGE_MASK);

	VM_BUG_ON(end   & ~PAGE_MASK);
@@ -187,9 +187,8 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma, 
		nr_pages--;

	}



	ret = __get_user_pages(current, mm, addr, nr_pages, gup_flags,

			       NULL, NULL);

	return max(ret, 0);	/* 0 or negative error code */

	return __get_user_pages(current, mm, addr, nr_pages, gup_flags,

				NULL, NULL, nonblocking);

}



/*
@@ -233,7 +232,7 @@ long mlock_vma_pages_range(struct vm_area_struct *vma, 
			is_vm_hugetlb_page(vma) ||

			vma == get_gate_vma(current))) {



		__mlock_vma_pages_range(vma, start, end);

		__mlock_vma_pages_range(vma, start, end, NULL);



		/* Hide errors from mmap() and other callers */

		return 0;
@@ -429,21 +428,23 @@ static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors) 
	struct mm_struct *mm = current->mm;

	unsigned long end, nstart, nend;

	struct vm_area_struct *vma = NULL;

	int locked = 0;

	int ret = 0;



	VM_BUG_ON(start & ~PAGE_MASK);

	VM_BUG_ON(len != PAGE_ALIGN(len));

	end = start + len;



	down_read(&mm->mmap_sem);

	for (nstart = start; nstart < end; nstart = nend) {

		/*

		 * We want to fault in pages for [nstart; end) address range.

		 * Find first corresponding VMA.

		 */

		if (!vma)

		if (!locked) {

			locked = 1;

			down_read(&mm->mmap_sem);

			vma = find_vma(mm, nstart);

		else

		} else if (nstart >= vma->vm_end)

			vma = vma->vm_next;

		if (!vma || vma->vm_start >= end)

			break;
@@ -457,18 +458,23 @@ static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors) 
		if (nstart < vma->vm_start)

			nstart = vma->vm_start;

		/*

		 * Now fault in a range of pages within the first VMA.

		 * Now fault in a range of pages. __mlock_vma_pages_range()

		 * double checks the vma flags, so that it won't mlock pages

		 * if the vma was already munlocked.

		 */

		ret = __mlock_vma_pages_range(vma, nstart, nend);

		if (ret < 0 && ignore_errors) {

		ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);

		if (ret < 0) {

			if (ignore_errors) {

				ret = 0;

				continue;	/* continue at next VMA */

			}

		if (ret) {

			ret = __mlock_posix_error_return(ret);

			break;

		}

		nend = nstart + ret * PAGE_SIZE;

		ret = 0;

	}

	if (locked)

		up_read(&mm->mmap_sem);

	return ret;	/* 0 or negative error code */

}

mm/nommu.c

+4 −2
Original line number Diff line number Diff line
@@ -127,7 +127,8 @@ unsigned int kobjsize(const void *objp) 


int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,

		     unsigned long start, int nr_pages, unsigned int foll_flags,

		     struct page **pages, struct vm_area_struct **vmas)

		     struct page **pages, struct vm_area_struct **vmas,

		     int *retry)

{

	struct vm_area_struct *vma;

	unsigned long vm_flags;
@@ -185,7 +186,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
	if (force)

		flags |= FOLL_FORCE;



	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);

	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,

				NULL);

}

EXPORT_SYMBOL(get_user_pages);