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[91.18.218.136]) by smtp.gmail.com with ESMTPSA id k23sm11646782wmj.32.2018.12.23.06.36.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 23 Dec 2018 06:36:05 -0800 (PST) From: Christian Brauner To: gregkh@linuxfoundation.org, tkjos@android.com, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Cc: arve@android.com, maco@android.com, joel@joelfernandes.org, Christian Brauner , Todd Kjos Subject: [PATCH v1 2/2] binderfs: reserve devices for initial mount Date: Sun, 23 Dec 2018 15:35:50 +0100 Message-Id: <20181223143550.10672-2-christian@brauner.io> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181223143550.10672-1-christian@brauner.io> References: <20181223143550.10672-1-christian@brauner.io> MIME-Version: 1.0 X-Patchwork-Bot: notify Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: Greg Kroah-Hartman Signed-off-by: Christian Brauner --- v1: - patch introduced v0: - patch not present --- drivers/android/binderfs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c index 873adda064ac..aa635c7ea727 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 a devices available. */ +#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4) static struct vfsmount *binderfs_mnt; @@ -129,11 +131,14 @@ 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; -- 2.19.1