give readdir(2)/getdents(2)/etc. uniform exclusion with lseek()

same as read() on regular files has, and for the same reason.

Signed-off-by: Al Viro <[e-mail]>

arch/alpha/kernel/osf_sys.c

···
 		long __user *, basep)
 {
 	int error;
-	struct fd arg = fdget(fd);
+	struct fd arg = fdget_pos(fd);
 	struct osf_dirent_callback buf = {
 		.ctx.actor = osf_filldir,
 		.dirent = dirent,
···
 	if (count != buf.count)
 		error = count - buf.count;
 
-	fdput(arg);
+	fdput_pos(arg);
 	return error;
 }
 

fs/compat.c

···
 		struct compat_old_linux_dirent __user *, dirent, unsigned int, count)
 {
 	int error;
-	struct fd f = fdget(fd);
+	struct fd f = fdget_pos(fd);
 	struct compat_readdir_callback buf = {
 		.ctx.actor = compat_fillonedir,
 		.dirent = dirent
···
 	if (buf.result)
 		error = buf.result;
 
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }
 
···
 	if (!access_ok(VERIFY_WRITE, dirent, count))
 		return -EFAULT;
 
-	f = fdget(fd);
+	f = fdget_pos(fd);
 	if (!f.file)
 		return -EBADF;
 
···
 		else
 			error = count - buf.count;
 	}
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }
 
···
 	if (!access_ok(VERIFY_WRITE, dirent, count))
 		return -EFAULT;
 
-	f = fdget(fd);
+	f = fdget_pos(fd);
 	if (!f.file)
 		return -EBADF;
 
···
 		else
 			error = count - buf.count;
 	}
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }
 #endif /* __ARCH_WANT_COMPAT_SYS_GETDENTS64 */

fs/file.c

···
 	return v;
 }
 
+void __f_unlock_pos(struct file *f)
+{
+	mutex_unlock(&f->f_pos_lock);
+}
+
 /*
  * We only lock f_pos if we have threads or if the file might be
  * shared with another process. In both cases we'll have an elevated

fs/open.c

···
 	}
 
 	/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
-	if (S_ISREG(inode->i_mode))
+	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 		f->f_mode |= FMODE_ATOMIC_POS;
 
 	f->f_op = fops_get(inode->i_fop);

fs/read_write.c

···
 }
 EXPORT_SYMBOL(vfs_llseek);
 
-static inline struct fd fdget_pos(int fd)
-{
-	return __to_fd(__fdget_pos(fd));
-}
-
-static inline void fdput_pos(struct fd f)
-{
-	if (f.flags & FDPUT_POS_UNLOCK)
-		mutex_unlock(&f.file->f_pos_lock);
-	fdput(f);
-}
-
 SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
 {
 	off_t retval;

fs/readdir.c

···
 		struct old_linux_dirent __user *, dirent, unsigned int, count)
 {
 	int error;
-	struct fd f = fdget(fd);
+	struct fd f = fdget_pos(fd);
 	struct readdir_callback buf = {
 		.ctx.actor = fillonedir,
 		.dirent = dirent
···
 	if (buf.result)
 		error = buf.result;
 
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }
 
···
 	if (!access_ok(VERIFY_WRITE, dirent, count))
 		return -EFAULT;
 
-	f = fdget(fd);
+	f = fdget_pos(fd);
 	if (!f.file)
 		return -EBADF;
 
···
 		else
 			error = count - buf.count;
 	}
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }
 
···
 	if (!access_ok(VERIFY_WRITE, dirent, count))
 		return -EFAULT;
 
-	f = fdget(fd);
+	f = fdget_pos(fd);
 	if (!f.file)
 		return -EBADF;
 
···
 		else
 			error = count - buf.count;
 	}
-	fdput(f);
+	fdput_pos(f);
 	return error;
 }

include/linux/file.h

···
 extern unsigned long __fdget(unsigned int fd);
 extern unsigned long __fdget_raw(unsigned int fd);
 extern unsigned long __fdget_pos(unsigned int fd);
+extern void __f_unlock_pos(struct file *);
 
 static inline struct fd __to_fd(unsigned long v)
 {
···
 static inline struct fd fdget_raw(unsigned int fd)
 {
 	return __to_fd(__fdget_raw(fd));
+}
+
+static inline struct fd fdget_pos(int fd)
+{
+	return __to_fd(__fdget_pos(fd));
+}
+
+static inline void fdput_pos(struct fd f)
+{
+	if (f.flags & FDPUT_POS_UNLOCK)
+		__f_unlock_pos(f.file);
+	fdput(f);
 }
 
 extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);