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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: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-11-01 16:55:19 -04:00
parent 651022382c
commit 8229706e03
2 changed files with 31 additions and 1 deletions
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30
lib/test_xarray.c
View File

@ -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);
}

2
lib/xarray.c
View File

@ -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;