[PATCH] libmount: if ENOMEDIUM and tray is open, close tray and retry

[Stanislav Brabec <sbrabec@suse.cz>]

In past, d50c5917 introduced an interesting behavior: If mount was called on a
CDROM with open tray, the tray was closed and mount was retried. But the
implementation caused 15 seconds delay, so ca55a451 reverted it.

This is another attempt to implement that:
If tray is closed: No change, no delay, no retry, simply fail.
If tray is open: Close tray and retry after 3 seconds.

It can never cause delay more than time to close tray + 3 sec.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
---
 libmount/src/context_mount.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index 65f7dbfd0..80cc2e8c8 100644
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -18,11 +18,15 @@
 
 #include <sys/wait.h>
 #include <sys/mount.h>
+#include <linux/cdrom.h>
 
 #include "linux_version.h"
 #include "mountP.h"
 #include "strutils.h"
 
+/* open() retries when errno is ENOMEDIUM and tray is open */
+#define CRDOM_TRAYOPEN_RETRIES    5
+
 /*
  * Kernel supports only one MS_PROPAGATION flag change by one mount(2) syscall,
  * to bypass this restriction we call mount(2) per flag. It's really not a perfect
@@ -1292,6 +1296,8 @@ int mnt_context_get_mount_excode(
 	int syserr;
 	struct stat st;
 	unsigned long uflags = 0, mflags = 0;
+	int cdrom;
+	unsigned int retries = 0;
 
 	int restricted = mnt_context_is_restricted(cxt);
 	const char *tgt = mnt_context_get_target(cxt);
@@ -1399,6 +1405,7 @@ int mnt_context_get_mount_excode(
 	/*
 	 * mount(2) errors
 	 */
+mount_retry:
 	syserr = mnt_context_get_syscall_errno(cxt);
 
 
@@ -1563,6 +1570,18 @@ int mnt_context_get_mount_excode(
 		break;
 
 	case ENOMEDIUM:
+		cdrom = open(mnt_context_get_source(cxt), O_RDONLY | O_NONBLOCK);
+		if (cdrom != -1) {
+			if (retries < CRDOM_TRAYOPEN_RETRIES &&
+			    ioctl(cdrom, CDROM_DRIVE_STATUS) == CDS_TRAY_OPEN) {
+				ioctl(cdrom, CDROMCLOSETRAY);
+				close(cdrom);
+				sleep(3);
+				++retries;
+				goto mount_retry;
+			} else
+				close(cdrom);
+		}
 		if (uflags & MNT_MS_NOFAIL)
 			return MNT_EX_SUCCESS;
 		if (buf)
-- 
2.13.2

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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