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authorChristian Brauner <christian@brauner.io>2019-01-11 11:19:40 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-01-11 13:42:15 +0100
commit36bdf3cae09df891b191f3955c8e54a2e05d67d0 (patch)
tree0bbdd8f9aad41f102f8a1d6941c97c2bbe2215d4 /drivers/android
parentc13295ad219d8bb0e47942d4cfc8251de449a67e (diff)
downloadlinux-36bdf3cae09df891b191f3955c8e54a2e05d67d0.tar.bz2
binderfs: reserve devices for initial mount
The binderfs instance in the initial ipc namespace will always have a reserve of 4 binder devices unless explicitly capped by specifying a lower value via the "max" mount option. This ensures when binder devices are removed (on accident or on purpose) they can always be recreated without risking that all minor numbers have already been used up. Cc: Todd Kjos <tkjos@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android')
-rw-r--r--drivers/android/binderfs.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index f6341893b5ba..ad3ad2f7f9f4 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -40,6 +40,8 @@
#define INODE_OFFSET 3
#define INTSTRLEN 21
#define BINDERFS_MAX_MINOR (1U << MINORBITS)
+/* Ensure that the initial ipc namespace always has devices available. */
+#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)
static dev_t binderfs_dev;
static DEFINE_MUTEX(binderfs_minors_mutex);
@@ -127,11 +129,14 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
struct inode *inode = NULL;
struct super_block *sb = ref_inode->i_sb;
struct binderfs_info *info = sb->s_fs_info;
+ bool use_reserve = (info->ipc_ns == &init_ipc_ns);
/* Reserve new minor number for the new device. */
mutex_lock(&binderfs_minors_mutex);
if (++info->device_count <= info->mount_opts.max)
- minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR,
+ minor = ida_alloc_max(&binderfs_minors,
+ use_reserve ? BINDERFS_MAX_MINOR :
+ BINDERFS_MAX_MINOR_CAPPED,
GFP_KERNEL);
else
minor = -ENOSPC;