inotify: convert to idr_alloc()

Convert to the much saner new idr interface.

Note that the adhoc cyclic id allocation is buggy.  If wraparound
happens, the previous code with idr_get_new_above() may segfault and
the converted code will trigger WARN and return -EINVAL.  Even if it's
fixed to wrap to zero, the code will be prone to unnecessary -ENOSPC
failures after the first wraparound.  We probably need to implement
proper cyclic support in idr.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Robert Love <rlove@rlove.org>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 13 deletions

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 07f7a92fe88e..e0f7c1241a6a 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -364,22 +364,20 @@ static int inotify_add_to_idr(struct idr *idr, spinlock_t *idr_lock,
 {
         int ret;
 
-        do {
-                if (unlikely(!idr_pre_get(idr, GFP_KERNEL)))
-                        return -ENOMEM;
+        idr_preload(GFP_KERNEL);
+        spin_lock(idr_lock);
 
-                spin_lock(idr_lock);
-                ret = idr_get_new_above(idr, i_mark, *last_wd + 1,
-                                        &i_mark->wd);
+        ret = idr_alloc(idr, i_mark, *last_wd + 1, 0, GFP_NOWAIT);
+        if (ret >= 0) {
                 /* we added the mark to the idr, take a reference */
-                if (!ret) {
-                        *last_wd = i_mark->wd;
-                        fsnotify_get_mark(&i_mark->fsn_mark);
-                }
-                spin_unlock(idr_lock);
-        } while (ret == -EAGAIN);
+                i_mark->wd = ret;
+                *last_wd = i_mark->wd;
+                fsnotify_get_mark(&i_mark->fsn_mark);
+        }
 
-        return ret;
+        spin_unlock(idr_lock);
+        idr_preload_end();
+        return ret < 0 ? ret : 0;
 }
 
 static struct inotify_inode_mark *inotify_idr_find_locked(struct fsnotify_group *group,