[RFC 08/10] lib/tida.c: introduce tida_get_above

[Rasmus Villemoes]

Some potential users want to impose a minimum on the returned
id. Extend tida_get to accept a start parameter, renaming it to
tida_get_above, and make tida_get a trivial wrapper.

Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk>
---
 include/linux/tida.h |  8 +++++++-
 lib/tida.c           | 22 +++++++++++++---------
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/include/linux/tida.h b/include/linux/tida.h
index 9aa3ad96a632..a76fe01bee0b 100644
--- a/include/linux/tida.h
+++ b/include/linux/tida.h
@@ -19,8 +19,14 @@ struct tida {
 void tida_init(struct tida *tida);
 void tida_destroy(struct tida *tida);
 
-int tida_get(struct tida *tida, gfp_t gfp);
+int tida_get_above(struct tida *tida, int start, gfp_t gfp);
 void tida_put(struct tida *tida, int id);
 
+static inline int
+tida_get(struct tida *tida, gfp_t gfp)
+{
+       return tida_get_above(tida, 0, gfp);
+}
+
 
 #endif /* __LINUX_TIDA_H__ */
diff --git a/lib/tida.c b/lib/tida.c
index 1ea0deb6fa64..0d43b207325a 100644
--- a/lib/tida.c
+++ b/lib/tida.c
@@ -23,16 +23,15 @@
  */
 
 static int
-tida_expand(struct tida *tida, gfp_t gfp, unsigned long *flags)
+tida_expand(struct tida *tida, gfp_t gfp, unsigned long *flags, unsigned long 
minalloc)
        __releases(tida->lock)
        __acquires(tida->lock)
 {
        unsigned long newalloc, oldalloc = tida->alloc;
        unsigned long *bits;
 
-       newalloc = oldalloc ? 2 * oldalloc : BITS_PER_LONG;
-
        spin_unlock_irqrestore(&tida->lock, *flags);
+       newalloc = max(2*oldalloc, round_up(minalloc, BITS_PER_LONG));
        bits = kcalloc(BITS_TO_LONGS(newalloc), sizeof(*bits), gfp);
        spin_lock_irqsave(&tida->lock, *flags);
 
@@ -50,29 +49,34 @@ tida_expand(struct tida *tida, gfp_t gfp, unsigned long 
*flags)
 }
 
 int
-tida_get(struct tida *tida, gfp_t gfp)
+tida_get_above(struct tida *tida, int start, gfp_t gfp)
 {
        unsigned long flags;
-       int ret;
+       int ret, from;
+
+       if (WARN_ON_ONCE(start < 0))
+               return -EINVAL;
 
        spin_lock_irqsave(&tida->lock, flags);
        while (1) {
                /* find_next_zero_bit is fine with a NULL bitmap as long as 
size is 0 */
-               ret = find_next_zero_bit(tida->bits, tida->alloc, tida->hint);
+               from = max(start, tida->hint);
+               ret = find_next_zero_bit(tida->bits, tida->alloc, from);
                if (ret < tida->alloc)
                        break;
-               ret = tida_expand(tida, gfp, &flags);
+               ret = tida_expand(tida, gfp, &flags, from + 1);
                if (ret < 0)
                        goto out;
        }
 
        __set_bit(ret, tida->bits);
-       tida->hint = ret+1;
+       if (start <= tida->hint)
+               tida->hint = ret + 1;
 out:
        spin_unlock_irqrestore(&tida->lock, flags);
        return ret;
 }
-EXPORT_SYMBOL_GPL(tida_get);
+EXPORT_SYMBOL_GPL(tida_get_above);
 
 void
 tida_put(struct tida *tida, int id)
-- 
2.1.4