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XArray: Permit storing 2-byte-aligned pointers

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On m68k, statically allocated pointers may only be two-byte aligned.
This clashes with the XArray's method for tagging internal pointers.
Permit storing these pointers in single slots (ie not in multislots).

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-12-28 23:20:44 -05:00
parent 4a31896c5b
commit 76b4e52995
3 changed files with 58 additions and 12 deletions
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18
include/linux/xarray.h
View File

@ -176,7 +176,8 @@ static inline bool xa_is_internal(const void *entry)
*/
static inline bool xa_is_err(const void *entry)
{
return unlikely(xa_is_internal(entry));
return unlikely(xa_is_internal(entry) &&
(unsigned long)entry >= -((MAX_ERRNO << 2) + 2));
}
/**
@ -1039,8 +1040,8 @@ static inline bool xa_is_sibling(const void *entry)
(entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
}
#define XA_ZERO_ENTRY xa_mk_internal(256)
#define XA_RETRY_ENTRY xa_mk_internal(257)
#define XA_RETRY_ENTRY xa_mk_internal(256)
#define XA_ZERO_ENTRY xa_mk_internal(257)
/**
* xa_is_zero() - Is the entry a zero entry?
@ -1064,6 +1065,17 @@ static inline bool xa_is_retry(const void *entry)
return unlikely(entry == XA_RETRY_ENTRY);
}
/**
* xa_is_advanced() - Is the entry only permitted for the advanced API?
* @entry: Entry to be stored in the XArray.
*
* Return: %true if the entry cannot be stored by the normal API.
*/
static inline bool xa_is_advanced(const void *entry)
{
return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
}
/**
* typedef xa_update_node_t - A callback function from the XArray.
* @node: The node which is being processed

30
lib/test_xarray.c
View File

@ -1184,6 +1184,35 @@ static noinline void check_store_range(struct xarray *xa)
}
}
static void check_align_1(struct xarray *xa, char *name)
{
int i;
unsigned int id;
unsigned long index;
void *entry;
for (i = 0; i < 8; i++) {
id = 0;
XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, name + i, GFP_KERNEL)
!= 0);
XA_BUG_ON(xa, id != i);
}
xa_for_each(xa, index, entry)
XA_BUG_ON(xa, xa_is_err(entry));
xa_destroy(xa);
}
static noinline void check_align(struct xarray *xa)
{
char name[] = "Motorola 68000";
check_align_1(xa, name);
check_align_1(xa, name + 1);
check_align_1(xa, name + 2);
check_align_1(xa, name + 3);
// check_align_2(xa, name);
}
static LIST_HEAD(shadow_nodes);
static void test_update_node(struct xa_node *node)
@ -1333,6 +1362,7 @@ static int xarray_checks(void)
check_create_range(&array);
check_store_range(&array);
check_store_iter(&array);
check_align(&xa0);
check_workingset(&array, 0);
check_workingset(&array, 64);

22
lib/xarray.c
View File

@ -232,6 +232,8 @@ void *xas_load(struct xa_state *xas)
if (xas->xa_shift > node->shift)
break;
entry = xas_descend(xas, node);
if (node->shift == 0)
break;
}
return entry;
}
@ -506,7 +508,7 @@ static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
for (;;) {
void *entry = xa_entry_locked(xas->xa, node, offset);
if (xa_is_node(entry)) {
if (node->shift && xa_is_node(entry)) {
node = xa_to_node(entry);
offset = 0;
continue;
@ -604,6 +606,7 @@ static int xas_expand(struct xa_state *xas, void *head)
/*
* xas_create() - Create a slot to store an entry in.
* @xas: XArray operation state.
* @allow_root: %true if we can store the entry in the root directly
*
* Most users will not need to call this function directly, as it is called
* by xas_store(). It is useful for doing conditional store operations
@ -613,7 +616,7 @@ static int xas_expand(struct xa_state *xas, void *head)
* If the slot was newly created, returns %NULL. If it failed to create the
* slot, returns %NULL and indicates the error in @xas.
*/
static void *xas_create(struct xa_state *xas)
static void *xas_create(struct xa_state *xas, bool allow_root)
{
struct xarray *xa = xas->xa;
void *entry;
@ -628,6 +631,8 @@ static void *xas_create(struct xa_state *xas)
shift = xas_expand(xas, entry);
if (shift < 0)
return NULL;
if (!shift && !allow_root)
shift = XA_CHUNK_SHIFT;
entry = xa_head_locked(xa);
slot = &xa->xa_head;
} else if (xas_error(xas)) {
@ -687,7 +692,7 @@ void xas_create_range(struct xa_state *xas)
xas->xa_sibs = 0;
for (;;) {
xas_create(xas);
xas_create(xas, true);
if (xas_error(xas))
goto restore;
if (xas->xa_index <= (index | XA_CHUNK_MASK))
@ -754,7 +759,7 @@ void *xas_store(struct xa_state *xas, void *entry)
bool value = xa_is_value(entry);
if (entry)
first = xas_create(xas);
first = xas_create(xas, !xa_is_node(entry));
else
first = xas_load(xas);
@ -1279,7 +1284,6 @@ static void *xas_result(struct xa_state *xas, void *curr)
{
if (xa_is_zero(curr))
return NULL;
XA_NODE_BUG_ON(xas->xa_node, xa_is_internal(curr));
if (xas_error(xas))
curr = xas->xa_node;
return curr;
@ -1349,7 +1353,7 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
XA_STATE(xas, xa, index);
void *curr;
if (WARN_ON_ONCE(xa_is_internal(entry)))
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return XA_ERROR(-EINVAL);
if (xa_track_free(xa) && !entry)
entry = XA_ZERO_ENTRY;
@ -1415,7 +1419,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
XA_STATE(xas, xa, index);
void *curr;
if (WARN_ON_ONCE(xa_is_internal(entry)))
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return XA_ERROR(-EINVAL);
if (xa_track_free(xa) && !entry)
entry = XA_ZERO_ENTRY;
@ -1538,7 +1542,7 @@ void *xa_store_range(struct xarray *xa, unsigned long first,
if (last + 1)
order = __ffs(last + 1);
xas_set_order(&xas, last, order);
xas_create(&xas);
xas_create(&xas, true);
if (xas_error(&xas))
goto unlock;
}
@ -1580,7 +1584,7 @@ int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
XA_STATE(xas, xa, 0);
int err;
if (WARN_ON_ONCE(xa_is_internal(entry)))
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return -EINVAL;
if (WARN_ON_ONCE(!xa_track_free(xa)))
return -EINVAL;