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XArray: Fix xa_find_after with multi-index entries 

If the entry is of an order which is a multiple of XA_CHUNK_SIZE,
the current detection of sibling entries does not work.  Factor out
an xas_sibling() function to make xa_find_after() a little more
understandable, and write a new implementation that doesn't suffer from
the same bug.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
This commit is contained in:
Matthew Wilcox (Oracle) 2020-01-17 22:00:41 -05:00
parent 430f24f94c
commit 19c30f4dd0
2 changed files with 32 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
lib/test_xarray.c
View File

@ -902,28 +902,30 @@ static noinline void check_store_iter(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
static noinline void check_multi_find(struct xarray *xa)
static noinline void check_multi_find_1(struct xarray *xa, unsigned order)
{
#ifdef CONFIG_XARRAY_MULTI
unsigned long multi = 3 << order;
unsigned long next = 4 << order;
unsigned long index;
xa_store_order(xa, 12, 2, xa_mk_value(12), GFP_KERNEL);
XA_BUG_ON(xa, xa_store_index(xa, 16, GFP_KERNEL) != NULL);
xa_store_order(xa, multi, order, xa_mk_value(multi), GFP_KERNEL);
XA_BUG_ON(xa, xa_store_index(xa, next, GFP_KERNEL) != NULL);
index = 0;
XA_BUG_ON(xa, xa_find(xa, &index, ULONG_MAX, XA_PRESENT) !=
xa_mk_value(12));
XA_BUG_ON(xa, index != 12);
index = 13;
xa_mk_value(multi));
XA_BUG_ON(xa, index != multi);
index = multi + 1;
XA_BUG_ON(xa, xa_find(xa, &index, ULONG_MAX, XA_PRESENT) !=
xa_mk_value(12));
XA_BUG_ON(xa, (index < 12) || (index >= 16));
xa_mk_value(multi));
XA_BUG_ON(xa, (index < multi) || (index >= next));
XA_BUG_ON(xa, xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT) !=
xa_mk_value(16));
XA_BUG_ON(xa, index != 16);
xa_mk_value(next));
XA_BUG_ON(xa, index != next);
xa_erase_index(xa, 12);
xa_erase_index(xa, 16);
xa_erase_index(xa, multi);
xa_erase_index(xa, next);
XA_BUG_ON(xa, !xa_empty(xa));
#endif
}
@ -1064,11 +1066,15 @@ static noinline void check_find_4(struct xarray *xa)
static noinline void check_find(struct xarray *xa)
{
unsigned i;
check_find_1(xa);
check_find_2(xa);
check_find_3(xa);
check_find_4(xa);
check_multi_find(xa);
for (i = 2; i < 10; i++)
check_multi_find_1(xa, i);
check_multi_find_2(xa);
}

20
lib/xarray.c
View File

@ -1826,6 +1826,17 @@ void *xa_find(struct xarray *xa, unsigned long *indexp,
}
EXPORT_SYMBOL(xa_find);
static bool xas_sibling(struct xa_state *xas)
{
struct xa_node *node = xas->xa_node;
unsigned long mask;
if (!node)
return false;
mask = (XA_CHUNK_SIZE << node->shift) - 1;
return (xas->xa_index & mask) > (xas->xa_offset << node->shift);
}
/**
* xa_find_after() - Search the XArray for a present entry.
* @xa: XArray.
@ -1860,13 +1871,8 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
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;
} else {
if (xas.xa_offset < (xas.xa_index & XA_CHUNK_MASK))
continue;
}
if (xas_sibling(&xas))
continue;
if (!xas_retry(&xas, entry))
break;
}