Btrfs: avoid null deref in unpin_extent_cache()

[safe/jmp/linux-2.6] / fs / file_table.c

diff --git a/fs/file_table.c b/fs/file_table.c
index 3d66dbc..334ce39 100644 (file)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -399,6 +399,44 @@ too_bad:
        return 0;
 }
 
+/**
+ *     mark_files_ro - mark all files read-only
+ *     @sb: superblock in question
+ *
+ *     All files are marked read-only.  We don't care about pending
+ *     delete files so this should be used in 'force' mode only.
+ */
+void mark_files_ro(struct super_block *sb)
+{
+       struct file *f;
+
+retry:
+       file_list_lock();
+       list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
+               struct vfsmount *mnt;
+               if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
+                      continue;
+               if (!file_count(f))
+                       continue;
+               if (!(f->f_mode & FMODE_WRITE))
+                       continue;
+               f->f_mode &= ~FMODE_WRITE;
+               if (file_check_writeable(f) != 0)
+                       continue;
+               file_release_write(f);
+               mnt = mntget(f->f_path.mnt);
+               file_list_unlock();
+               /*
+                * This can sleep, so we can't hold
+                * the file_list_lock() spinlock.
+                */
+               mnt_drop_write(mnt);
+               mntput(mnt);
+               goto retry;
+       }
+       file_list_unlock();
+}
+
 void __init files_init(unsigned long mempages)
 { 
        int n;