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>

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 9580abe..ce2d954 100644 (file)
--- 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;