ipc: convert to idr_alloc()

Convert to the much saner new idr interface.

The new interface doesn't directly translate to the way idr_pre_get()
was used around ipc_addid() as preloading disables preemption.  From
my cursory reading, it seems like we should be able to do all
allocation from ipc_addid(), so I moved it there.  Can you please
check whether this would be okay?  If this is wrong and ipc_addid()
should be allowed to be called from non-sleepable context, I'd suggest
allocating id itself in the outer functions and later install the
pointer using idr_replace().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 21 deletions

diff --git a/ipc/util.c b/ipc/util.c
index 74e1d9c7a98a..464a8abd779f 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -252,7 +252,7 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
         kuid_t euid;
         kgid_t egid;
-        int id, err;
+        int id;
         int next_id = ids->next_id;
 
         if (size > IPCMNI)
@@ -261,17 +261,21 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
         if (ids->in_use >= size)
                 return -ENOSPC;
 
+        idr_preload(GFP_KERNEL);
+
         spin_lock_init(&new->lock);
         new->deleted = 0;
         rcu_read_lock();
         spin_lock(&new->lock);
 
-        err = idr_get_new_above(&ids->ipcs_idr, new,
-                                (next_id < 0) ? 0 : ipcid_to_idx(next_id), &id);
-        if (err) {
+        id = idr_alloc(&ids->ipcs_idr, new,
+                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
+                       GFP_NOWAIT);
+        idr_preload_end();
+        if (id < 0) {
                 spin_unlock(&new->lock);
                 rcu_read_unlock();
-                return err;
+                return id;
         }
 
         ids->in_use++;
@@ -307,19 +311,10 @@ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
                 struct ipc_ops *ops, struct ipc_params *params)
 {
         int err;
-retry:
-        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
-
-        if (!err)
-                return -ENOMEM;
 
         down_write(&ids->rw_mutex);
         err = ops->getnew(ns, params);
         up_write(&ids->rw_mutex);
-
-        if (err == -EAGAIN)
-                goto retry;
-
         return err;
 }
 
@@ -376,8 +371,6 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
         struct kern_ipc_perm *ipcp;
         int flg = params->flg;
         int err;
-retry:
-        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 
         /*
          * Take the lock as a writer since we are potentially going to add
@@ -389,8 +382,6 @@ retry:
                 /* key not used */
                 if (!(flg & IPC_CREAT))
                         err = -ENOENT;
-                else if (!err)
-                        err = -ENOMEM;
                 else
                         err = ops->getnew(ns, params);
         } else {
@@ -413,9 +404,6 @@ retry:
         }
         up_write(&ids->rw_mutex);
 
-        if (err == -EAGAIN)
-                goto retry;
-
         return err;
 }