fs/proc: calculate /proc/* and /proc/*/task/* nlink at init time

Runtime nlink calculation works but meh.  I don't know how to do it at
compile time, but I know how to do it at init time.

Shift "2+" part into init time as a bonus.

Link: http://lkml.kernel.org/r/20161122195549.GB29812@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 04a5fcad4c34..9b99df4893a4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -104,6 +104,9 @@
  *      in /proc for a task before it execs a suid executable.
  */
 
+static u8 nlink_tid;
+static u8 nlink_tgid;
+
 struct pid_entry {
         const char *name;
         unsigned int len;
@@ -139,13 +142,13 @@ struct pid_entry {
  * Count the number of hardlinks for the pid_entry table, excluding the .
  * and .. links.
  */
-static unsigned int pid_entry_count_dirs(const struct pid_entry *entries,
+static unsigned int __init pid_entry_nlink(const struct pid_entry *entries,
         unsigned int n)
 {
         unsigned int i;
         unsigned int count;
 
-        count = 0;
+        count = 2;
         for (i = 0; i < n; ++i) {
                 if (S_ISDIR(entries[i].mode))
                         ++count;
@@ -3068,8 +3071,7 @@ static int proc_pid_instantiate(struct inode *dir,
         inode->i_fop = &proc_tgid_base_operations;
         inode->i_flags|=S_IMMUTABLE;
 
-        set_nlink(inode, 2 + pid_entry_count_dirs(tgid_base_stuff,
-                                                  ARRAY_SIZE(tgid_base_stuff)));
+        set_nlink(inode, nlink_tgid);
 
         d_set_d_op(dentry, &pid_dentry_operations);
 
@@ -3361,8 +3363,7 @@ static int proc_task_instantiate(struct inode *dir,
         inode->i_fop = &proc_tid_base_operations;
         inode->i_flags|=S_IMMUTABLE;
 
-        set_nlink(inode, 2 + pid_entry_count_dirs(tid_base_stuff,
-                                                  ARRAY_SIZE(tid_base_stuff)));
+        set_nlink(inode, nlink_tid);
 
         d_set_d_op(dentry, &pid_dentry_operations);
 
@@ -3552,3 +3553,9 @@ static const struct file_operations proc_task_operations = {
         .iterate_shared = proc_task_readdir,
         .llseek         = generic_file_llseek,
 };
+
+void __init set_proc_pid_nlink(void)
+{
+        nlink_tid = pid_entry_nlink(tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
+        nlink_tgid = pid_entry_nlink(tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
+}