s390: simplify dynamic sysctl registration for appldata_register_ops

The routine appldata_register_ops() allocates a sysctl table
with 4 entries. The firsts one,   ops->ctl_table[0] is the parent directory
with an empty entry following it, ops->ctl_table[1]. The next entry is
for the ops->name and that is     ops->ctl_table[2]. It needs an empty
entry following that, and that is ops->ctl_table[3]. And so hence the
kcalloc(4, sizeof(struct ctl_table), GFP_KERNEL).

We can simplify this considerably since sysctl_register("foo", table)
can create the parent directory for us if it does not exist. So we
can just remove the first two entries and move back the ops->name to
the first entry, and just use kcalloc(2, ...).

[gor@linux.ibm.com: appldata_generic_handler fixup ctl_table index 2->0]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20230310234525.3986352-7-mcgrof@kernel.org
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
index c593f22280830f47d00fab6547d9bd796a8307f7..b07b0610950ee99efeae6957f4de5b35cd52d5ff 100644 (file)
--- a/arch/s390/appldata/appldata_base.c
+++ b/arch/s390/appldata/appldata_base.c
@@ -281,7 +281,7 @@ appldata_generic_handler(struct ctl_table *ctl, int write,
        mutex_lock(&appldata_ops_mutex);
        list_for_each(lh, &appldata_ops_list) {
                tmp_ops = list_entry(lh, struct appldata_ops, list);
-               if (&tmp_ops->ctl_table[2] == ctl) {
+               if (&tmp_ops->ctl_table[0] == ctl) {
                        found = 1;
                }
        }
@@ -351,7 +351,8 @@ int appldata_register_ops(struct appldata_ops *ops)
        if (ops->size > APPLDATA_MAX_REC_SIZE)
                return -EINVAL;
 
-       ops->ctl_table = kcalloc(4, sizeof(struct ctl_table), GFP_KERNEL);
+       /* The last entry must be an empty one */
+       ops->ctl_table = kcalloc(2, sizeof(struct ctl_table), GFP_KERNEL);
        if (!ops->ctl_table)
                return -ENOMEM;
 
@@ -359,17 +360,12 @@ int appldata_register_ops(struct appldata_ops *ops)
        list_add(&ops->list, &appldata_ops_list);
        mutex_unlock(&appldata_ops_mutex);
 
-       ops->ctl_table[0].procname = appldata_proc_name;
-       ops->ctl_table[0].maxlen   = 0;
-       ops->ctl_table[0].mode     = S_IRUGO | S_IXUGO;
-       ops->ctl_table[0].child    = &ops->ctl_table[2];
+       ops->ctl_table[0].procname = ops->name;
+       ops->ctl_table[0].mode = S_IRUGO | S_IWUSR;
+       ops->ctl_table[0].proc_handler = appldata_generic_handler;
+       ops->ctl_table[0].data = ops;
 
-       ops->ctl_table[2].procname = ops->name;
-       ops->ctl_table[2].mode     = S_IRUGO | S_IWUSR;
-       ops->ctl_table[2].proc_handler = appldata_generic_handler;
-       ops->ctl_table[2].data = ops;
-
-       ops->sysctl_header = register_sysctl_table(ops->ctl_table);
+       ops->sysctl_header = register_sysctl(appldata_proc_name, ops->ctl_table);
        if (!ops->sysctl_header)
                goto out;
        return 0;