radix-tree: must check __radix_tree_preload() return value

__radix_tree_preload() only disables preemption if no error is returned.

So we really need to make sure callers always check the return value.

idr_preload() contract is to always disable preemption, so we need
to add a missing preempt_disable() if an error happened.

Similarly, ida_pre_get() only needs to call preempt_enable() in the
case no error happened.

Link: http://lkml.kernel.org/r/1504637190.15310.62.camel@edumazet-glaptop3.roam.corp.google.com
Fixes: 0a835c4f090a ("Reimplement IDR and IDA using the radix tree")
Fixes: 7ad3d4d85c7a ("ida: Move ida_bitmap to a percpu variable")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>    [4.11+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 9717e2a503746c0e5a01b2e570bcd3d74d31c837..8b1feca1230a08c4537036f517cfa4369b62dffa 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -463,7 +463,7 @@ radix_tree_node_free(struct radix_tree_node *node)
  * To make use of this facility, the radix tree must be initialised without
  * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
  */
-static int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
+static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
 {
        struct radix_tree_preload *rtp;
        struct radix_tree_node *node;
@@ -2104,7 +2104,8 @@ EXPORT_SYMBOL(radix_tree_tagged);
  */
 void idr_preload(gfp_t gfp_mask)
 {
-       __radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE);
+       if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
+               preempt_disable();
 }
 EXPORT_SYMBOL(idr_preload);
 
@@ -2118,13 +2119,13 @@ EXPORT_SYMBOL(idr_preload);
  */
 int ida_pre_get(struct ida *ida, gfp_t gfp)
 {
-       __radix_tree_preload(gfp, IDA_PRELOAD_SIZE);
        /*
         * The IDA API has no preload_end() equivalent.  Instead,
         * ida_get_new() can return -EAGAIN, prompting the caller
         * to return to the ida_pre_get() step.
         */
-       preempt_enable();
+       if (!__radix_tree_preload(gfp, IDA_PRELOAD_SIZE))
+               preempt_enable();
 
        if (!this_cpu_read(ida_bitmap)) {
                struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);