[PATCH] files: fix preemption issues

With the new fdtable locking rules, you have to protect fdtable with either
->file_lock or rcu_read_lock/unlock().  There are some places where we
aren't doing either.  This patch fixes those places.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/fs/locks.c b/fs/locks.c
index c2c09b4798d6..f7daa5f48949 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -124,6 +124,7 @@
 #include <linux/smp_lock.h>
 #include <linux/syscalls.h>
 #include <linux/time.h>
+#include <linux/rcupdate.h>
 
 #include <asm/semaphore.h>
 #include <asm/uaccess.h>
@@ -2205,6 +2206,7 @@ void steal_locks(fl_owner_t from)
 
         lock_kernel();
         j = 0;
+        rcu_read_lock();
         fdt = files_fdtable(files);
         for (;;) {
                 unsigned long set;
@@ -2222,6 +2224,7 @@ void steal_locks(fl_owner_t from)
                         set >>= 1;
                 }
         }
+        rcu_read_unlock();
         unlock_kernel();
 }
 EXPORT_SYMBOL(steal_locks);
diff --git a/fs/proc/array.c b/fs/proc/array.c
index d88d518d30f6..d84eecacbeaf 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -74,6 +74,7 @@
 #include <linux/file.h>
 #include <linux/times.h>
 #include <linux/cpuset.h>
+#include <linux/rcupdate.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -180,12 +181,14 @@ static inline char * task_state(struct task_struct *p, char *buffer)
                 p->gid, p->egid, p->sgid, p->fsgid);
         read_unlock(&tasklist_lock);
         task_lock(p);
+        rcu_read_lock();
         if (p->files)
                 fdt = files_fdtable(p->files);
         buffer += sprintf(buffer,
                 "FDSize:\t%d\n"
                 "Groups:\t",
                 fdt ? fdt->max_fds : 0);
+        rcu_read_unlock();
 
         group_info = p->group_info;
         get_group_info(group_info);