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authorMatthew Wilcox <willy@infradead.org>2019-01-02 13:57:03 -0500
committerMatthew Wilcox <willy@infradead.org>2019-01-06 22:12:58 -0500
commitb0606fed6eece16a421034eca0bbea9a08b90e91 (patch)
treef705b58760a60fce2d6f03a934a5038154505c1b
parent76b4e52995654af260f14558e0e07b5b039ae202 (diff)
XArray: Honour reserved entries in xa_insert
xa_insert() should treat reserved entries as occupied, not as available. Also, it should treat requests to insert a NULL pointer as a request to reserve the slot. Add xa_insert_bh() and xa_insert_irq() for completeness. Signed-off-by: Matthew Wilcox <willy@infradead.org>
-rw-r--r--Documentation/core-api/xarray.rst15
-rw-r--r--include/linux/xarray.h110
-rw-r--r--lib/test_xarray.c8
-rw-r--r--lib/xarray.c41
4 files changed, 126 insertions, 48 deletions
diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst
index 6a6d67acaf69..5d54b27c6eba 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -108,12 +108,13 @@ some, but not all of the other indices changing.
Sometimes you need to ensure that a subsequent call to :c:func:`xa_store`
will not need to allocate memory. The :c:func:`xa_reserve` function
-will store a reserved entry at the indicated index. Users of the normal
-API will see this entry as containing ``NULL``. If you do not need to
-use the reserved entry, you can call :c:func:`xa_release` to remove the
-unused entry. If another user has stored to the entry in the meantime,
-:c:func:`xa_release` will do nothing; if instead you want the entry to
-become ``NULL``, you should use :c:func:`xa_erase`.
+will store a reserved entry at the indicated index. Users of the
+normal API will see this entry as containing ``NULL``. If you do
+not need to use the reserved entry, you can call :c:func:`xa_release`
+to remove the unused entry. If another user has stored to the entry
+in the meantime, :c:func:`xa_release` will do nothing; if instead you
+want the entry to become ``NULL``, you should use :c:func:`xa_erase`.
+Using :c:func:`xa_insert` on a reserved entry will fail.
If all entries in the array are ``NULL``, the :c:func:`xa_empty` function
will return ``true``.
@@ -183,6 +184,8 @@ Takes xa_lock internally:
* :c:func:`xa_store_bh`
* :c:func:`xa_store_irq`
* :c:func:`xa_insert`
+ * :c:func:`xa_insert_bh`
+ * :c:func:`xa_insert_irq`
* :c:func:`xa_erase`
* :c:func:`xa_erase_bh`
* :c:func:`xa_erase_irq`
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 435c25b29079..12244aa98a69 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -463,40 +463,13 @@ void *__xa_erase(struct xarray *, unsigned long index);
void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
void *entry, gfp_t);
+int __xa_insert(struct xarray *, unsigned long index, void *entry, gfp_t);
int __xa_alloc(struct xarray *, u32 *id, u32 max, void *entry, gfp_t);
int __xa_reserve(struct xarray *, unsigned long index, gfp_t);
void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
/**
- * __xa_insert() - Store this entry in the XArray unless another entry is
- * already present.
- * @xa: XArray.
- * @index: Index into array.
- * @entry: New entry.
- * @gfp: Memory allocation flags.
- *
- * If you would rather see the existing entry in the array, use __xa_cmpxchg().
- * This function is for users who don't care what the entry is, only that
- * one is present.
- *
- * Context: Any context. Expects xa_lock to be held on entry. May
- * release and reacquire xa_lock if the @gfp flags permit.
- * Return: 0 if the store succeeded. -EEXIST if another entry was present.
- * -ENOMEM if memory could not be allocated.
- */
-static inline int __xa_insert(struct xarray *xa, unsigned long index,
- void *entry, gfp_t gfp)
-{
- void *curr = __xa_cmpxchg(xa, index, NULL, entry, gfp);
- if (!curr)
- return 0;
- if (xa_is_err(curr))
- return xa_err(curr);
- return -EEXIST;
-}
-
-/**
* xa_store_bh() - Store this entry in the XArray.
* @xa: XArray.
* @index: Index into array.
@@ -685,24 +658,83 @@ static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
* @entry: New entry.
* @gfp: Memory allocation flags.
*
- * If you would rather see the existing entry in the array, use xa_cmpxchg().
- * This function is for users who don't care what the entry is, only that
- * one is present.
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present. Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
*
- * Context: Process context. Takes and releases the xa_lock.
- * May sleep if the @gfp flags permit.
+ * Context: Any context. Takes and releases the xa_lock. May sleep if
+ * the @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int xa_insert(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
- void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
- if (!curr)
- return 0;
- if (xa_is_err(curr))
- return xa_err(curr);
- return -EEXIST;
+ int err;
+
+ xa_lock(xa);
+ err = __xa_insert(xa, index, entry, gfp);
+ xa_unlock(xa);
+
+ return err;
+}
+
+/**
+ * xa_insert_bh() - Store this entry in the XArray unless another entry is
+ * already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present. Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Any context. Takes and releases the xa_lock while
+ * disabling softirqs. May sleep if the @gfp flags permit.
+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int xa_insert_bh(struct xarray *xa, unsigned long index,
+ void *entry, gfp_t gfp)
+{
+ int err;
+
+ xa_lock_bh(xa);
+ err = __xa_insert(xa, index, entry, gfp);
+ xa_unlock_bh(xa);
+
+ return err;
+}
+
+/**
+ * xa_insert_irq() - Store this entry in the XArray unless another entry is
+ * already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present. Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Process context. Takes and releases the xa_lock while
+ * disabling interrupts. May sleep if the @gfp flags permit.
+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int xa_insert_irq(struct xarray *xa, unsigned long index,
+ void *entry, gfp_t gfp)
+{
+ int err;
+
+ xa_lock_irq(xa);
+ err = __xa_insert(xa, index, entry, gfp);
+ xa_unlock_irq(xa);
+
+ return err;
}
/**
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 6e0212a60b08..3cf17338b0a4 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -382,10 +382,12 @@ static noinline void check_reserve(struct xarray *xa)
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
- /* And so does xa_insert */
+ /* But xa_insert does not */
xa_reserve(xa, 12345678, GFP_KERNEL);
- XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) != 0);
- xa_erase_index(xa, 12345678);
+ XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) !=
+ -EEXIST);
+ XA_BUG_ON(xa, xa_empty(xa));
+ XA_BUG_ON(xa, xa_erase(xa, 12345678) != NULL);
XA_BUG_ON(xa, !xa_empty(xa));
/* Can iterate through a reserved entry */
diff --git a/lib/xarray.c b/lib/xarray.c
index bffa26b1f0d6..81c3171ddde9 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1440,6 +1440,47 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
EXPORT_SYMBOL(__xa_cmpxchg);
/**
+ * __xa_insert() - Store this entry in the XArray if no entry is present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present. Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Any context. Expects xa_lock to be held on entry. May
+ * release and reacquire xa_lock if @gfp flags permit.
+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
+{
+ XA_STATE(xas, xa, index);
+ void *curr;
+
+ 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, -EEXIST);
+ }
+ } while (__xas_nomem(&xas, gfp));
+
+ return xas_error(&xas);
+}
+EXPORT_SYMBOL(__xa_insert);
+
+/**
* __xa_reserve() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.