Commit 8229706e authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

XArray: Fix xa_for_each with a single element at 0 



The following sequence of calls would result in an infinite loop in
xa_find_after():

	xa_store(xa, 0, x, GFP_KERNEL);
	index = 0;
	xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { }

xa_find_after() was confusing the situation where we found no entry in
the tree with finding a multiorder entry, so it would look for the
successor entry forever.  Just check for this case explicitly.  Includes
a few new checks in the test suite to be sure this doesn't reappear.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent 65102238

lib/test_xarray.c

+29 −1
Original line number Diff line number Diff line
@@ -702,7 +702,7 @@ static noinline void check_multi_find_2(struct xarray *xa) 
	}

}



static noinline void check_find(struct xarray *xa)

static noinline void check_find_1(struct xarray *xa)

{

	unsigned long i, j, k;
@@ -748,6 +748,34 @@ static noinline void check_find(struct xarray *xa) 
		XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_0));

	}

	XA_BUG_ON(xa, !xa_empty(xa));

}



static noinline void check_find_2(struct xarray *xa)

{

	void *entry;

	unsigned long i, j, index = 0;



	xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {

		XA_BUG_ON(xa, true);

	}



	for (i = 0; i < 1024; i++) {

		xa_store_index(xa, index, GFP_KERNEL);

		j = 0;

		index = 0;

		xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {

			XA_BUG_ON(xa, xa_mk_value(index) != entry);

			XA_BUG_ON(xa, index != j++);

		}

	}



	xa_destroy(xa);

}



static noinline void check_find(struct xarray *xa)

{

	check_find_1(xa);

	check_find_2(xa);

	check_multi_find(xa);

	check_multi_find_2(xa);

}

lib/xarray.c

+2 −0
Original line number Diff line number Diff line
@@ -1829,6 +1829,8 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp, 
			entry = xas_find_marked(&xas, max, filter);

		else

			entry = xas_find(&xas, max);

		if (xas.xa_node == XAS_BOUNDS)

			break;

		if (xas.xa_shift) {

			if (xas.xa_index & ((1UL << xas.xa_shift) - 1))

				continue;

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