IB/uverbs: Use anon_inodes instead of private infinibandeventfs

The anon_inodes interface has been split to allow creating a bare
(non-installed) file pointer and also extended to allow specifying
O_RDONLY in the flags.  This makes it a suitable replacement for the
private "infinibandeventfs" pseudo-filesystem used by uverbs, and this
replacement saves a small chunk of boilerplate code.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 5 insertions, 56 deletions

diff --git a/drivers/infiniband/Kconfig b/drivers/infiniband/Kconfig
index dd0db67bf8d..975adce5f40 100644
--- a/drivers/infiniband/Kconfig
+++ b/drivers/infiniband/Kconfig
@@ -20,6 +20,7 @@ config INFINIBAND_USER_MAD
 
 config INFINIBAND_USER_ACCESS
         tristate "InfiniBand userspace access (verbs and CM)"
+        select ANON_INODES
         ---help---
           Userspace InfiniBand access support.  This enables the
           kernel side of userspace verbs and the userspace
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 5f284ffd430..82b60c65dd4 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -42,8 +42,8 @@
 #include <linux/poll.h>
 #include <linux/sched.h>
 #include <linux/file.h>
-#include <linux/mount.h>
 #include <linux/cdev.h>
+#include <linux/anon_inodes.h>
 
 #include <asm/uaccess.h>
 
@@ -53,8 +53,6 @@ MODULE_AUTHOR("Roland Dreier");
 MODULE_DESCRIPTION("InfiniBand userspace verbs access");
 MODULE_LICENSE("Dual BSD/GPL");
 
-#define INFINIBANDEVENTFS_MAGIC 0x49426576      /* "IBev" */
-
 enum {
         IB_UVERBS_MAJOR       = 231,
         IB_UVERBS_BASE_MINOR  = 192,
@@ -111,8 +109,6 @@ static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
         [IB_USER_VERBS_CMD_DESTROY_SRQ]         = ib_uverbs_destroy_srq,
 };
 
-static struct vfsmount *uverbs_event_mnt;
-
 static void ib_uverbs_add_one(struct ib_device *device);
 static void ib_uverbs_remove_one(struct ib_device *device);
 
@@ -492,7 +488,6 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
                                         int is_async, int *fd)
 {
         struct ib_uverbs_event_file *ev_file;
-        struct path path;
         struct file *filp;
         int ret;
 
@@ -515,27 +510,16 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
                 goto err;
         }
 
-        /*
-         * fops_get() can't fail here, because we're coming from a
-         * system call on a uverbs file, which will already have a
-         * module reference.
-         */
-        path.mnt = uverbs_event_mnt;
-        path.dentry = uverbs_event_mnt->mnt_root;
-        path_get(&path);
-        filp = alloc_file(&path, FMODE_READ, fops_get(&uverbs_event_fops));
+        filp = anon_inode_getfile("[uverbs-event]", &uverbs_event_fops,
+                                  ev_file, O_RDONLY);
         if (!filp) {
                 ret = -ENFILE;
                 goto err_fd;
         }
 
-        filp->private_data = ev_file;
-
         return filp;
 
 err_fd:
-        fops_put(&uverbs_event_fops);
-        path_put(&path);
         put_unused_fd(*fd);
 
 err:
@@ -825,21 +809,6 @@ static void ib_uverbs_remove_one(struct ib_device *device)
         kfree(uverbs_dev);
 }
 
-static int uverbs_event_get_sb(struct file_system_type *fs_type, int flags,
-                               const char *dev_name, void *data,
-                               struct vfsmount *mnt)
-{
-        return get_sb_pseudo(fs_type, "infinibandevent:", NULL,
-                             INFINIBANDEVENTFS_MAGIC, mnt);
-}
-
-static struct file_system_type uverbs_event_fs = {
-        /* No owner field so module can be unloaded */
-        .name    = "infinibandeventfs",
-        .get_sb  = uverbs_event_get_sb,
-        .kill_sb = kill_litter_super
-};
-
 static int __init ib_uverbs_init(void)
 {
         int ret;
@@ -864,33 +833,14 @@ static int __init ib_uverbs_init(void)
                 goto out_class;
         }
 
-        ret = register_filesystem(&uverbs_event_fs);
-        if (ret) {
-                printk(KERN_ERR "user_verbs: couldn't register infinibandeventfs\n");
-                goto out_class;
-        }
-
-        uverbs_event_mnt = kern_mount(&uverbs_event_fs);
-        if (IS_ERR(uverbs_event_mnt)) {
-                ret = PTR_ERR(uverbs_event_mnt);
-                printk(KERN_ERR "user_verbs: couldn't mount infinibandeventfs\n");
-                goto out_fs;
-        }
-
         ret = ib_register_client(&uverbs_client);
         if (ret) {
                 printk(KERN_ERR "user_verbs: couldn't register client\n");
-                goto out_mnt;
+                goto out_class;
         }
 
         return 0;
 
-out_mnt:
-        mntput(uverbs_event_mnt);
-
-out_fs:
-        unregister_filesystem(&uverbs_event_fs);
-
 out_class:
         class_destroy(uverbs_class);
 
@@ -904,8 +854,6 @@ out:
 static void __exit ib_uverbs_cleanup(void)
 {
         ib_unregister_client(&uverbs_client);
-        mntput(uverbs_event_mnt);
-        unregister_filesystem(&uverbs_event_fs);
         class_destroy(uverbs_class);
         unregister_chrdev_region(IB_UVERBS_BASE_DEV, IB_UVERBS_MAX_DEVICES);
         idr_destroy(&ib_uverbs_pd_idr);