proc: stop using BKL

There are four BKL users in proc: de_put(), proc_lookup_de(),
proc_readdir_de(), proc_root_readdir(),

1) de_put()
-----------
de_put() is classic atomic_dec_and_test() refcount wrapper -- no BKL
needed. BKL doesn't matter to possible refcount leak as well.

2) proc_lookup_de()
-------------------
Walking PDE list is protected by proc_subdir_lock(), proc_get_inode() is
potentially blocking, all callers of proc_lookup_de() eventually end up
from ->lookup hooks which is protected by directory's ->i_mutex -- BKL
doesn't protect anything.

3) proc_readdir_de()
--------------------
"." and ".." part doesn't need BKL, walking PDE list is under
proc_subdir_lock, calling filldir callback is potentially blocking
because it writes to luserspace. All proc_readdir_de() callers
eventually come from ->readdir hook which is under directory's
->i_mutex -- BKL doesn't protect anything.

4) proc_root_readdir_de()
-------------------------
proc_root_readdir_de is ->readdir hook, see (3).

Since readdir hooks doesn't use BKL anymore, switch to
generic_file_llseek, since it also takes directory's i_mutex.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

1 files changed, 2 insertions, 6 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 60a359b35582..db7fa5cab988 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -14,7 +14,6 @@
 #include <linux/stat.h>
 #include <linux/module.h>
 #include <linux/mount.h>
-#include <linux/smp_lock.h>
 #include <linux/init.h>
 #include <linux/idr.h>
 #include <linux/namei.h>
@@ -379,7 +378,6 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
         struct inode *inode = NULL;
         int error = -ENOENT;
 
-        lock_kernel();
         spin_lock(&proc_subdir_lock);
         for (de = de->subdir; de ; de = de->next) {
                 if (de->namelen != dentry->d_name.len)
@@ -397,7 +395,6 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
         }
         spin_unlock(&proc_subdir_lock);
 out_unlock:
-        unlock_kernel();
 
         if (inode) {
                 dentry->d_op = &proc_dentry_operations;
@@ -432,8 +429,6 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
         struct inode *inode = filp->f_path.dentry->d_inode;
         int ret = 0;
 
-        lock_kernel();
-
         ino = inode->i_ino;
         i = filp->f_pos;
         switch (i) {
@@ -487,7 +482,7 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
                         spin_unlock(&proc_subdir_lock);
         }
         ret = 1;
-out:    unlock_kernel();
+out:
         return ret;     
 }
 
@@ -504,6 +499,7 @@ int proc_readdir(struct file *filp, void *dirent, filldir_t filldir)
  * the /proc directory.
  */
 static const struct file_operations proc_dir_operations = {
+        .llseek                 = generic_file_llseek,
         .read                   = generic_read_dir,
         .readdir                = proc_readdir,
 };