idr: remove _idr_rc_to_errno() hack

idr uses -1, IDR_NEED_TO_GROW and IDR_NOMORE_SPACE to communicate
exception conditions internally.  The return value is later translated
to errno values using _idr_rc_to_errno().

This is confusing.  Drop the custom ones and consistently use -EAGAIN
for "tree needs to grow", -ENOMEM for "need more memory" and -ENOSPC for
"ran out of ID space".

Due to the weird memory preloading mechanism, [ra]_get_new*() return
-EAGAIN on memory shortage, so we need to substitute -ENOMEM w/
-EAGAIN on those interface functions.  They'll eventually be cleaned
up and the translations will go away.

This patch doesn't introduce any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 12 deletions

diff --git a/lib/idr.c b/lib/idr.c
index 282841b5a561..bde6eecb0e87 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -133,6 +133,21 @@ int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
 }
 EXPORT_SYMBOL(idr_pre_get);
 
+/**
+ * sub_alloc - try to allocate an id without growing the tree depth
+ * @idp: idr handle
+ * @starting_id: id to start search at
+ * @id: pointer to the allocated handle
+ * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
+ *
+ * Allocate an id in range [@starting_id, INT_MAX] from @idp without
+ * growing its depth.  Returns
+ *
+ *  the allocated id >= 0 if successful,
+ *  -EAGAIN if the tree needs to grow for allocation to succeed,
+ *  -ENOSPC if the id space is exhausted,
+ *  -ENOMEM if more idr_layers need to be allocated.
+ */
 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
 {
         int n, m, sh;
@@ -161,7 +176,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
                         /* if already at the top layer, we need to grow */
                         if (id >= 1 << (idp->layers * IDR_BITS)) {
                                 *starting_id = id;
-                                return IDR_NEED_TO_GROW;
+                                return -EAGAIN;
                         }
                         p = pa[l];
                         BUG_ON(!p);
@@ -180,7 +195,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
                         id = ((id >> sh) ^ n ^ m) << sh;
                 }
                 if ((id >= MAX_IDR_BIT) || (id < 0))
-                        return IDR_NOMORE_SPACE;
+                        return -ENOSPC;
                 if (l == 0)
                         break;
                 /*
@@ -189,7 +204,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
                 if (!p->ary[m]) {
                         new = get_from_free_list(idp);
                         if (!new)
-                                return -1;
+                                return -ENOMEM;
                         new->layer = l-1;
                         rcu_assign_pointer(p->ary[m], new);
                         p->count++;
@@ -215,7 +230,7 @@ build_up:
         layers = idp->layers;
         if (unlikely(!p)) {
                 if (!(p = get_from_free_list(idp)))
-                        return -1;
+                        return -ENOMEM;
                 p->layer = 0;
                 layers = 1;
         }
@@ -246,7 +261,7 @@ build_up:
                                 __move_to_free_list(idp, new);
                         }
                         spin_unlock_irqrestore(&idp->lock, flags);
-                        return -1;
+                        return -ENOMEM;
                 }
                 new->ary[0] = p;
                 new->count = 1;
@@ -258,7 +273,7 @@ build_up:
         rcu_assign_pointer(idp->top, p);
         idp->layers = layers;
         v = sub_alloc(idp, &id, pa);
-        if (v == IDR_NEED_TO_GROW)
+        if (v == -EAGAIN)
                 goto build_up;
         return(v);
 }
@@ -306,12 +321,8 @@ int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
         int rv;
 
         rv = idr_get_new_above_int(idp, ptr, starting_id);
-        /*
-         * This is a cheap hack until the IDR code can be fixed to
-         * return proper error values.
-         */
         if (rv < 0)
-                return _idr_rc_to_errno(rv);
+                return rv == -ENOMEM ? -EAGAIN : rv;
         *id = rv;
         return 0;
 }
@@ -766,7 +777,7 @@ int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
         /* get vacant slot */
         t = idr_get_empty_slot(&ida->idr, idr_id, pa);
         if (t < 0)
-                return _idr_rc_to_errno(t);
+                return t == -ENOMEM ? -EAGAIN : t;
 
         if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT)
                 return -ENOSPC;