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, 1 insertions, 7 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 7761602af9d..f6299a25594 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -16,7 +16,6 @@
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/bitops.h>
-#include <linux/smp_lock.h>
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
 
@@ -162,17 +161,12 @@ static int proc_root_readdir(struct file * filp,
 	unsigned int nr = filp->f_pos;
 	int ret;
 
-	lock_kernel();
-
 	if (nr < FIRST_PROCESS_ENTRY) {
 		int error = proc_readdir(filp, dirent, filldir);
-		if (error <= 0) {
-			unlock_kernel();
+		if (error <= 0)
 			return error;
-		}
 		filp->f_pos = FIRST_PROCESS_ENTRY;
 	}
-	unlock_kernel();
 
 	ret = proc_pid_readdir(filp, dirent, filldir);
 	return ret;