[PATCH v3 2/3] cdrom: gdrom: update gendisk capacity on open

Florian Fuchs
2026-04-23T20:21:03Z

Update the gendisk capacity of the media. Without the capacity, the block
reads fail before reaching the request queue, which prevented ISO9660
mounts. Refresh the capacity from the TOC leadout in gdrom_bdops_open()
so it checks the inserted media.

Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v2->v3: Also add quirk to handle proprietary GDROMs, using the same
mechanic like in gdrom_get_last_session() try session 1 first
for GDROM, then session 0 for CDROMs. Dropped Acked-By due to
code change.
v1->v2: no change for gdrom_update_capacity(), but for
gdrom_bdops_open(): handle the failure case when
gdrom_update_capacity() fails but previous cdrom_open() succeeded,
to cleanup the successful cdrom_open() with cdrom_release()

v2: https://lore.kernel.org/linux-sh/20260419162823.2829286-3-fuchsfl@gmail.com/
v1: https://lore.kernel.org/linux-sh/20260405082330.4104672-3-fuchsfl@gmail.com/

drivers/cdrom/gdrom.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)

diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 094d55b2d004..1e73617b39ac 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -474,6 +474,27 @@ static const struct cdrom_device_ops gdrom_ops = {
CDC_RESET | CDC_DRIVE_STATUS | CDC_CD_R,
};

+static int gdrom_update_capacity(void)
+{
+ sector_t cap;
+ int ret;
+
+ if (gdrom_drivestatus(gd.cd_info, CDSL_CURRENT) != CDS_DISC_OK) {
+ set_capacity(gd.disk, 0);
+ return -ENOMEDIUM;
+ }
+ ret = gdrom_readtoc_cmd(gd.toc, 1);
+ if (ret)
+ ret = gdrom_readtoc_cmd(gd.toc, 0);
+ if (ret) {
+ set_capacity(gd.disk, 0);
+ return ret;
+ }
+ cap = (sector_t)get_entry_lba(gd.toc->leadout) * GD_TO_BLK;
+ set_capacity(gd.disk, cap);
+ return 0;
+}
+
static int gdrom_bdops_open(struct gendisk *disk, blk_mode_t mode)
{
int ret;
@@ -482,6 +503,12 @@ static int gdrom_bdops_open(struct gendisk *disk, blk_mode_t mode)

mutex_lock(&gdrom_mutex);
ret = cdrom_open(gd.cd_info, mode);
+ if (ret)
+ goto out;
+ ret = gdrom_update_capacity();
+ if (ret)
+ cdrom_release(gd.cd_info);
+out:
mutex_unlock(&gdrom_mutex);
return ret;
}
--
2.43.0