[PATCH] make st seekable again

Apparently `tar' errors out if it cannot perform lseek() against a tape.  Work
around that in-kernel.
Signed-off-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/ide/ide-tape.c

@@ -4100,7 +4100,13 @@ static int idetape_chrdev_open (struct inode *inode, struct file *filp)
 	idetape_pc_t pc;
 	int retval;
 
-	nonseekable_open(inode, filp);
+	/*
+	 * We really want to do nonseekable_open(inode, filp); here, but some
+	 * versions of tar incorrectly call lseek on tapes and bail out if that
+	 * fails.  So we disallow pread() and pwrite(), but permit lseeks.
+	 */
+	filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
+
 #if IDETAPE_DEBUG_LOG
 	printk(KERN_INFO "ide-tape: Reached idetape_chrdev_open\n");
 #endif /* IDETAPE_DEBUG_LOG */

drivers/scsi/osst.c

@@ -4318,7 +4318,13 @@ static int os_scsi_tape_open(struct inode * inode, struct file * filp)
 	int		      dev  = TAPE_NR(inode);
 	int		      mode = TAPE_MODE(inode);
 
-	nonseekable_open(inode, filp);
+	/*
+	 * We really want to do nonseekable_open(inode, filp); here, but some
+	 * versions of tar incorrectly call lseek on tapes and bail out if that
+	 * fails.  So we disallow pread() and pwrite(), but permit lseeks.
+	 */
+	filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
+
 	write_lock(&os_scsi_tapes_lock);
 	if (dev >= osst_max_dev || os_scsi_tapes == NULL ||
 	    (STp = os_scsi_tapes[dev]) == NULL || !STp->device) {

drivers/scsi/st.c

@@ -1004,7 +1004,13 @@ static int st_open(struct inode *inode, struct file *filp)
 	int dev = TAPE_NR(inode);
 	char *name;
 
-	nonseekable_open(inode, filp);
+	/*
+	 * We really want to do nonseekable_open(inode, filp); here, but some
+	 * versions of tar incorrectly call lseek on tapes and bail out if that
+	 * fails.  So we disallow pread() and pwrite(), but permit lseeks.
+	 */
+	filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
+
 	write_lock(&st_dev_arr_lock);
 	if (dev >= st_dev_max || scsi_tapes == NULL ||
 	    ((STp = scsi_tapes[dev]) == NULL)) {