[PATCH] proc: Fix the link count for /proc/<pid>/task

Use getattr to get an accurate link count when needed.  This is cheaper and
more accurate than trying to derive it by walking the thread list of a
process.

Especially as it happens when needed stat instead of at readdir time.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a85b073408e0129e5ddab6d82610b4dd46dc7529..29539c2268a3cec9c7622e5103a08157f0249cca 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1532,6 +1532,7 @@ out:
 
 static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldir);
 static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd);
+static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
 
 static struct file_operations proc_fd_operations = {
        .read           = generic_read_dir,
@@ -1552,6 +1553,7 @@ static struct inode_operations proc_fd_inode_operations = {
 
 static struct inode_operations proc_task_inode_operations = {
        .lookup         = proc_task_lookup,
+       .getattr        = proc_task_getattr,
 };
 
 #ifdef CONFIG_SECURITY
@@ -1658,7 +1660,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
         */
        switch(p->type) {
                case PROC_TGID_TASK:
-                       inode->i_nlink = 2 + get_tid_list(2, NULL, dir);
+                       inode->i_nlink = 2;
                        inode->i_op = &proc_task_inode_operations;
                        inode->i_fop = &proc_task_operations;
                        break;
@@ -2261,7 +2263,6 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
        }
 
        nr_tids = get_tid_list(pos, tid_array, inode);
-       inode->i_nlink = pos + nr_tids;
 
        for (i = 0; i < nr_tids; i++) {
                unsigned long j = PROC_NUMBUF;
@@ -2281,3 +2282,19 @@ out:
        filp->f_pos = pos;
        return retval;
 }
+
+static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+       struct inode *inode = dentry->d_inode;
+       struct task_struct *p = proc_task(inode);
+       generic_fillattr(inode, stat);
+
+       if (pid_alive(p)) {
+               task_lock(p);
+               if (p->signal)
+                       stat->nlink += atomic_read(&p->signal->count);
+               task_unlock(p);
+       }
+
+       return 0;
+}