vfs: don't use BKL in default_llseek

There are currently 191 users of default_llseek.
Nine of these are in device drivers that use the
big kernel lock. None of these ever touch
file->f_pos outside of llseek or file_pos_write.

Consequently, we never rely on the BKL
in the default_llseek function and can
replace that with i_mutex, which is also
used in generic_file_llseek.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/fs/read_write.c b/fs/read_write.c
index 74e3658..fd09f61 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -124,7 +124,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
 {
        loff_t retval;
 
-       lock_kernel();
+       mutex_lock(&file->f_dentry->d_inode->i_mutex);
        switch (origin) {
                case SEEK_END:
                        offset += i_size_read(file->f_path.dentry->d_inode);
@@ -145,7 +145,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
                retval = offset;
        }
 out:
-       unlock_kernel();
+       mutex_unlock(&file->f_dentry->d_inode->i_mutex);
        return retval;
 }
 EXPORT_SYMBOL(default_llseek);