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Subject[PATCH v3 1/4] binder: add a mount option to show global stats
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Currently, all binder state and statistics live in debugfs.
We need this information even when debugfs is not mounted.
This patch adds the mount option 'stats' to enable a binderfs
instance to have binder debug information present in the same.
'stats=global' will enable the global binder statistics. In
the future, 'stats=local' will enable binder statistics local
to the binderfs instance. The two modes 'global' and 'local'
will be mutually exclusive. 'stats=global' option is only available
for a binderfs instance mounted in the initial user namespace.
An attempt to use the option to mount a binderfs instance in
another user namespace will return an EPERM error.

Signed-off-by: Hridya Valsaraju <hridya@google.com>
---

Changes in v2:
- Improve error check in binderfs_parse_mount_opts() as per Greg
Kroah-Hartman.
- Change pr_info() log before failure to pr_err() as per Greg
Kroah-Hartman.

drivers/android/binderfs.c | 45 ++++++++++++++++++++++++++++++++++++--
1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index cc2e71576396..7045bfe5b52b 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -51,18 +51,27 @@ static DEFINE_IDA(binderfs_minors);
/**
* binderfs_mount_opts - mount options for binderfs
* @max: maximum number of allocatable binderfs binder devices
+ * @stats_mode: enable binder stats in binderfs.
*/
struct binderfs_mount_opts {
int max;
+ int stats_mode;
};

enum {
Opt_max,
+ Opt_stats_mode,
Opt_err
};

+enum binderfs_stats_mode {
+ STATS_NONE,
+ STATS_GLOBAL,
+};
+
static const match_table_t tokens = {
{ Opt_max, "max=%d" },
+ { Opt_stats_mode, "stats=%s" },
{ Opt_err, NULL }
};

@@ -290,8 +299,9 @@ static void binderfs_evict_inode(struct inode *inode)
static int binderfs_parse_mount_opts(char *data,
struct binderfs_mount_opts *opts)
{
- char *p;
+ char *p, *stats;
opts->max = BINDERFS_MAX_MINOR;
+ opts->stats_mode = STATS_NONE;

while ((p = strsep(&data, ",")) != NULL) {
substring_t args[MAX_OPT_ARGS];
@@ -311,6 +321,22 @@ static int binderfs_parse_mount_opts(char *data,

opts->max = max_devices;
break;
+ case Opt_stats_mode:
+ if (!capable(CAP_SYS_ADMIN))
+ return -EINVAL;
+
+ stats = match_strdup(&args[0]);
+ if (!stats)
+ return -ENOMEM;
+
+ if (strcmp(stats, "global") != 0) {
+ kfree(stats);
+ return -EINVAL;
+ }
+
+ opts->stats_mode = STATS_GLOBAL;
+ kfree(stats);
+ break;
default:
pr_err("Invalid mount options\n");
return -EINVAL;
@@ -322,8 +348,21 @@ static int binderfs_parse_mount_opts(char *data,

static int binderfs_remount(struct super_block *sb, int *flags, char *data)
{
+ int prev_stats_mode, ret;
struct binderfs_info *info = sb->s_fs_info;
- return binderfs_parse_mount_opts(data, &info->mount_opts);
+
+ prev_stats_mode = info->mount_opts.stats_mode;
+ ret = binderfs_parse_mount_opts(data, &info->mount_opts);
+ if (ret)
+ return ret;
+
+ if (prev_stats_mode != info->mount_opts.stats_mode) {
+ pr_err("Binderfs stats mode cannot be changed during a remount\n");
+ info->mount_opts.stats_mode = prev_stats_mode;
+ return -EINVAL;
+ }
+
+ return 0;
}

static int binderfs_show_mount_opts(struct seq_file *seq, struct dentry *root)
@@ -333,6 +372,8 @@ static int binderfs_show_mount_opts(struct seq_file *seq, struct dentry *root)
info = root->d_sb->s_fs_info;
if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
seq_printf(seq, ",max=%d", info->mount_opts.max);
+ if (info->mount_opts.stats_mode == STATS_GLOBAL)
+ seq_printf(seq, ",stats=global");

return 0;
}
--
2.23.0.187.g17f5b7556c-goog
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