[PATCH v3] xarray: Document necessary flag in alloc-functions

Philipp Stanner
2023-09-11T21:50:52Z

Calling functions that wrap __xa_alloc() or __xa_alloc_cyclic() without
the xarray previously having been initialized with the flag
XA_FLAGS_ALLOC being set in xa_init_flags() results in undefined
behavior.

Document the necessity of setting this flag in all docstrings of
functions that wrap said two functions.

Signed-off-by: Philipp Stanner <pstanner@redhat.com>
---
I used the time available until we can get this merged to create a
version-3, improving a few things.

Changes since v2:
- Phrase the comment differently: say "requires [...] an xarray [...]"
instead of "must be operated on".
- Improve the commit message and use the canonical format: a) describe
the problem, b) name the solution in imperative form.

Regards,
P.
---
include/linux/xarray.h | 18 ++++++++++++++++++
lib/xarray.c | 6 ++++++
2 files changed, 24 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 741703b45f61..746a17b64aa6 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -856,6 +856,9 @@ static inline int __must_check xa_insert_irq(struct xarray *xa,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
@@ -886,6 +889,9 @@ static inline __must_check int xa_alloc(struct xarray *xa, u32 *id,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
@@ -916,6 +922,9 @@ static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
@@ -949,6 +958,9 @@ static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
@@ -983,6 +995,9 @@ static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
@@ -1017,6 +1032,9 @@ static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
diff --git a/lib/xarray.c b/lib/xarray.c
index 2071a3718f4e..2b07c332d26b 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1802,6 +1802,9 @@ EXPORT_SYMBOL(xa_get_order);
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* Context: Any context. Expects xa_lock to be held on entry. May
* release and reacquire xa_lock if @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
@@ -1850,6 +1853,9 @@ EXPORT_SYMBOL(__xa_alloc);
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
+ * Requires the xarray to be initialized with flag XA_FLAGS_ALLOC set
+ * in xa_init_flags().
+ *
* 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 allocation succeeded without wrapping. 1 if the
--
2.41.0