proc: do translation + unlink atomically at remove_proc_entry()

remove_proc_entry() does

	lock
	lookup parent
	unlock
	lock
	unlink proc entry from lists
	unlock

which can be made bit more correct by doing parent translation + unlink
without dropping lock.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 12 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 9580abeadeb3..ce2d95477701 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -291,19 +291,17 @@ static const struct inode_operations proc_file_inode_operations = {
  * returns the struct proc_dir_entry for "/proc/tty/driver", and
  * returns "serial" in residual.
  */
-static int xlate_proc_name(const char *name,
-                           struct proc_dir_entry **ret, const char **residual)
+static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
+                             const char **residual)
 {
         const char              *cp = name, *next;
         struct proc_dir_entry   *de;
         int                     len;
-        int                     rtn = 0;
 
         de = *ret;
         if (!de)
                 de = &proc_root;
 
-        spin_lock(&proc_subdir_lock);
         while (1) {
                 next = strchr(cp, '/');
                 if (!next)
@@ -314,17 +312,24 @@ static int xlate_proc_name(const char *name,
                         if (proc_match(len, cp, de))
                                 break;
                 }
-                if (!de) {
-                        rtn = -ENOENT;
-                        goto out;
-                }
+                if (!de)
+                        return -ENOENT;
                 cp += len + 1;
         }
         *residual = cp;
         *ret = de;
-out:
+        return 0;
+}
+
+static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
+                           const char **residual)
+{
+        int rv;
+
+        spin_lock(&proc_subdir_lock);
+        rv = __xlate_proc_name(name, ret, residual);
         spin_unlock(&proc_subdir_lock);
-        return rtn;
+        return rv;
 }
 
 static DEFINE_IDA(proc_inum_ida);
@@ -797,11 +802,13 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
         const char *fn = name;
         int len;
 
-        if (xlate_proc_name(name, &parent, &fn) != 0)
+        spin_lock(&proc_subdir_lock);
+        if (__xlate_proc_name(name, &parent, &fn) != 0) {
+                spin_unlock(&proc_subdir_lock);
                 return;
+        }
         len = strlen(fn);
 
-        spin_lock(&proc_subdir_lock);
         for (p = &parent->subdir; *p; p=&(*p)->next ) {
                 if (proc_match(len, fn, *p)) {
                         de = *p;