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Subject[PATCH v3 1/2] idr: Add ida_simple_get_cyclic
Date
Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
---
include/linux/idr.h | 8 +++++--
lib/idr.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index e856f4e0ab35..f151ce89124a 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -218,10 +218,12 @@ DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);

struct ida {
struct radix_tree_root ida_rt;
+ unsigned int ida_next;
};

-#define IDA_INIT(name) { \
- .ida_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER | GFP_NOWAIT), \
+#define IDA_INIT(name) { \
+ .ida_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER | GFP_NOWAIT), \
+ .ida_next = 0, \
}
#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)

@@ -232,6 +234,8 @@ void ida_destroy(struct ida *ida);

int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
gfp_t gfp_mask);
+int ida_simple_get_cyclic(struct ida *ida, unsigned int start, unsigned int end,
+ gfp_t gfp_mask);
void ida_simple_remove(struct ida *ida, unsigned int id);

static inline void ida_init(struct ida *ida)
diff --git a/lib/idr.c b/lib/idr.c
index 823b813f08f8..3374c3fa4027 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -599,6 +599,72 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
return ret;
}
EXPORT_SYMBOL(ida_simple_get);
+/**
+ * ida_simple_get_cyclic - get a new id.
+ * @ida: the (initialized) ida.
+ * @start: the minimum id (inclusive, < 0x8000000)
+ * @end: the maximum id (exclusive, < 0x8000000 or 0)
+ * @gfp_mask: memory allocation flags
+ *
+ * Allocates an id in the range start <= id < end, or returns -ENOSPC.
+ * On memory allocation failure, returns -ENOMEM.
+ * The search for an unused id will start at the last id allocated and will
+ * wrap around to @start if no free ids are found before reaching @end.
+ *
+ * Compared to ida_get_new_above() this function does its own locking, and
+ * should be used unless there are special requirements.
+ *
+ * Use ida_simple_remove() to get rid of an id.
+ */
+int ida_simple_get_cyclic(struct ida *ida, unsigned int start, unsigned int end,
+ gfp_t gfp_mask)
+{
+ int ret, id, next;
+ unsigned int max;
+ unsigned long flags;
+
+ WARN_ON((int)start < 0);
+ WARN_ON((int)end < 0);
+
+ if (end == 0) {
+ max = 0x80000000;
+ } else {
+ WARN_ON(end < start);
+ max = end - 1;
+ }
+
+again:
+ if (!ida_pre_get(ida, gfp_mask))
+ return -ENOMEM;
+
+ spin_lock_irqsave(&simple_ida_lock, flags);
+ next = ida->ida_next;
+ if (next < start || next >= end)
+ next = start;
+
+ ret = ida_get_new_above(ida, next, &id);
+ if (likely(!ret)) {
+ if (unlikely(id >= max)) {
+ ida_remove(ida, id);
+ if (next == start) {
+ ret = -ENOSPC;
+ } else {
+ ida->ida_next = start;
+ spin_unlock_irqrestore(&simple_ida_lock, flags);
+ goto again;
+ }
+ } else {
+ ida->ida_next = id + 1;
+ ret = id;
+ }
+ }
+ spin_unlock_irqrestore(&simple_ida_lock, flags);
+
+ if (unlikely(ret == -EAGAIN))
+ goto again;
+ return ret;
+}
+EXPORT_SYMBOL(ida_simple_get_cyclic);

/**
* ida_simple_remove - remove an allocated id.
--
2.14.3
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