isofs: Remove global fs lock

sbi->s_mutex isn't needed for isofs at all so we can just remove it. Generally,
since isofs is always mounted read-only, filesystem structure cannot change
under us.  So buffer_head contents stays constant after it's filled in. That
leaves us with possible changes of global data structures. Superblock changes
only during filesystem mount (even remount does not change it), inodes are only
filled in during reading from disk. So there are no changes of these structures
to bother about.

Arguments why sbi->s_mutex can be removed at each place:
isofs_readdir: Accesses sb, inode, filp, local variables => s_mutex not needed
isofs_lookup: Protected by directory's i_mutex. Accesses sb, inode, dentry,
  local variables => s_mutex not needed
rock_ridge_symlink_readpage: Protected by page lock. Accesses sb, inode,
  local variables => s_mutex not needed.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 0 insertions, 3 deletions

diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index 0542b6eedf80..f20437c068a0 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -254,19 +254,16 @@ static int isofs_readdir(struct file *filp,
         char *tmpname;
         struct iso_directory_record *tmpde;
         struct inode *inode = filp->f_path.dentry->d_inode;
-        struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
 
         tmpname = (char *)__get_free_page(GFP_KERNEL);
         if (tmpname == NULL)
                 return -ENOMEM;
 
-        mutex_lock(&sbi->s_mutex);
         tmpde = (struct iso_directory_record *) (tmpname+1024);
 
         result = do_isofs_readdir(inode, filp, dirent, filldir, tmpname, tmpde);
 
         free_page((unsigned long) tmpname);
-        mutex_unlock(&sbi->s_mutex);
         return result;
 }