* [PATCH 1/2] xarray: extract xa_zero_to_null
2024-11-12 19:25 [PATCH 0/2] xarray: extract __xa_cmpxchg_raw Tamir Duberstein
@ 2024-11-12 19:25 ` Tamir Duberstein
2024-11-12 19:25 ` [PATCH 2/2] xarray: extract helper from __xa_{insert,cmpxchg} Tamir Duberstein
1 sibling, 0 replies; 3+ messages in thread
From: Tamir Duberstein @ 2024-11-12 19:25 UTC (permalink / raw)
To: Andrew Morton, Matthew Wilcox
Cc: linux-fsdevel, linux-kernel, Alice Ryhl, Andreas Hindborg,
Tamir Duberstein
Reduce code duplication by extracting a static inline function that
returns its argument if it is non-zero and NULL otherwise.
This changes xas_result to check for errors before checking for zero but
this cannot change the behavior of existing callers:
- __xa_erase: passes the result of xas_store(_, NULL) which cannot fail.
- __xa_store: passes the result of xas_store(_, entry) which may fail.
xas_store calls xas_create when entry is not NULL which returns NULL
on error, which is immediately checked. This should not change
observable behavior.
- __xa_cmpxchg: passes the result of xas_load(_) which might be zero.
This would previously return NULL regardless of the outcome of
xas_store but xas_store cannot fail if xas_load returns zero
because there is no need to allocate memory.
- xa_store_range: same as __xa_erase.
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
lib/xarray.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/lib/xarray.c b/lib/xarray.c
index 32d4bac8c94ca13e11f350c6bcfcacc2040d0359..1b8305bffbff07adb80334fc83b5dc8e40ba2f50 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -435,6 +435,11 @@ static unsigned long max_index(void *entry)
return (XA_CHUNK_SIZE << xa_to_node(entry)->shift) - 1;
}
+static inline void *xa_zero_to_null(void *entry)
+{
+ return xa_is_zero(entry) ? NULL : entry;
+}
+
static void xas_shrink(struct xa_state *xas)
{
struct xarray *xa = xas->xa;
@@ -451,8 +456,8 @@ static void xas_shrink(struct xa_state *xas)
break;
if (!xa_is_node(entry) && node->shift)
break;
- if (xa_is_zero(entry) && xa_zero_busy(xa))
- entry = NULL;
+ if (xa_zero_busy(xa))
+ entry = xa_zero_to_null(entry);
xas->xa_node = XAS_BOUNDS;
RCU_INIT_POINTER(xa->xa_head, entry);
@@ -1474,9 +1479,7 @@ void *xa_load(struct xarray *xa, unsigned long index)
rcu_read_lock();
do {
- entry = xas_load(&xas);
- if (xa_is_zero(entry))
- entry = NULL;
+ entry = xa_zero_to_null(xas_load(&xas));
} while (xas_retry(&xas, entry));
rcu_read_unlock();
@@ -1486,11 +1489,9 @@ EXPORT_SYMBOL(xa_load);
static void *xas_result(struct xa_state *xas, void *curr)
{
- if (xa_is_zero(curr))
- return NULL;
if (xas_error(xas))
curr = xas->xa_node;
- return curr;
+ return xa_zero_to_null(curr);
}
/**
--
2.47.0
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH 2/2] xarray: extract helper from __xa_{insert,cmpxchg}
2024-11-12 19:25 [PATCH 0/2] xarray: extract __xa_cmpxchg_raw Tamir Duberstein
2024-11-12 19:25 ` [PATCH 1/2] xarray: extract xa_zero_to_null Tamir Duberstein
@ 2024-11-12 19:25 ` Tamir Duberstein
1 sibling, 0 replies; 3+ messages in thread
From: Tamir Duberstein @ 2024-11-12 19:25 UTC (permalink / raw)
To: Andrew Morton, Matthew Wilcox
Cc: linux-fsdevel, linux-kernel, Alice Ryhl, Andreas Hindborg,
Tamir Duberstein
Reduce code duplication by extracting a static inline function. This
function is identical to __xa_cmpxchg with the exception that it does
not coerce zero entries to null on the return path.
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
lib/xarray.c | 37 ++++++++++++++++++-------------------
1 file changed, 18 insertions(+), 19 deletions(-)
diff --git a/lib/xarray.c b/lib/xarray.c
index 1b8305bffbff07adb80334fc83b5dc8e40ba2f50..2af86bede3c119060650ee8b891751531c6732e7 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1491,7 +1491,7 @@ static void *xas_result(struct xa_state *xas, void *curr)
{
if (xas_error(xas))
curr = xas->xa_node;
- return xa_zero_to_null(curr);
+ return curr;
}
/**
@@ -1568,7 +1568,7 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
xas_clear_mark(&xas, XA_FREE_MARK);
} while (__xas_nomem(&xas, gfp));
- return xas_result(&xas, curr);
+ return xas_result(&xas, xa_zero_to_null(curr));
}
EXPORT_SYMBOL(__xa_store);
@@ -1601,6 +1601,9 @@ void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
}
EXPORT_SYMBOL(xa_store);
+static inline void *__xa_cmpxchg_raw(struct xarray *xa, unsigned long index,
+ void *old, void *entry, gfp_t gfp);
+
/**
* __xa_cmpxchg() - Store this entry in the XArray.
* @xa: XArray.
@@ -1619,6 +1622,13 @@ EXPORT_SYMBOL(xa_store);
*/
void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
+{
+ return xa_zero_to_null(__xa_cmpxchg_raw(xa, index, old, entry, gfp));
+}
+EXPORT_SYMBOL(__xa_cmpxchg);
+
+static inline void *__xa_cmpxchg_raw(struct xarray *xa, unsigned long index,
+ void *old, void *entry, gfp_t gfp)
{
XA_STATE(xas, xa, index);
void *curr;
@@ -1637,7 +1647,6 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
return xas_result(&xas, curr);
}
-EXPORT_SYMBOL(__xa_cmpxchg);
/**
* __xa_insert() - Store this entry in the XArray if no entry is present.
@@ -1657,26 +1666,16 @@ EXPORT_SYMBOL(__xa_cmpxchg);
*/
int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
{
- XA_STATE(xas, xa, index);
void *curr;
+ int errno;
- if (WARN_ON_ONCE(xa_is_advanced(entry)))
- return -EINVAL;
if (!entry)
entry = XA_ZERO_ENTRY;
-
- do {
- curr = xas_load(&xas);
- if (!curr) {
- xas_store(&xas, entry);
- if (xa_track_free(xa))
- xas_clear_mark(&xas, XA_FREE_MARK);
- } else {
- xas_set_err(&xas, -EBUSY);
- }
- } while (__xas_nomem(&xas, gfp));
-
- return xas_error(&xas);
+ curr = __xa_cmpxchg_raw(xa, index, NULL, entry, gfp);
+ errno = xa_err(curr);
+ if (errno)
+ return errno;
+ return (curr != NULL) ? -EBUSY : 0;
}
EXPORT_SYMBOL(__xa_insert);
--
2.47.0
^ permalink raw reply [flat|nested] 3+ messages in thread