UBI: introduce volume refcounting
Add ref_count field to UBI volumes and remove weired "vol->removed"
field. This way things are better understandable and we do not have
to do whold show_attr operation under spinlock.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 3d6ac02..18ef1e1 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -63,21 +63,24 @@
* B. process 2 removes volume Y;
* C. process 1 starts reading the /<sysfs>/class/ubi/ubiX_Y/reserved_ebs file;
*
- * What we want to do in a situation like that is to return error when the file
- * is read. This is done by means of the 'removed' flag and the 'vol_lock' of
- * the UBI volume description object.
+ * In this situation, this function will return %-ENODEV because it will find
+ * out that the volume was removed from the @ubi->volumes array.
*/
static ssize_t vol_attribute_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- int ret = -ENODEV;
+ int ret;
struct ubi_volume *vol = container_of(dev, struct ubi_volume, dev);
+ struct ubi_device *ubi = vol->ubi;
- spin_lock(&vol->ubi->volumes_lock);
- if (vol->removed) {
- spin_unlock(&vol->ubi->volumes_lock);
- return ret;
+ spin_lock(&ubi->volumes_lock);
+ if (!ubi->volumes[vol->vol_id]) {
+ spin_unlock(&ubi->volumes_lock);
+ return -ENODEV;
}
+ /* Take a reference to prevent volume removal */
+ vol->ref_count += 1;
+ spin_unlock(&ubi->volumes_lock);
if (attr == &attr_vol_reserved_ebs)
ret = sprintf(buf, "%d\n", vol->reserved_pebs);
@@ -102,8 +105,13 @@
else if (attr == &attr_vol_upd_marker)
ret = sprintf(buf, "%d\n", vol->upd_marker);
else
- BUG();
- spin_unlock(&vol->ubi->volumes_lock);
+ /* This must be a bug */
+ ret = -EINVAL;
+
+ spin_lock(&ubi->volumes_lock);
+ vol->ref_count -= 1;
+ ubi_assert(vol->ref_count >= 0);
+ spin_unlock(&ubi->volumes_lock);
return ret;
}
@@ -179,7 +187,7 @@
* @req: volume creation request
*
* This function creates volume described by @req. If @req->vol_id id
- * %UBI_VOL_NUM_AUTO, this function automatically assigne ID to the new volume
+ * %UBI_VOL_NUM_AUTO, this function automatically assign ID to the new volume
* and saves it in @req->vol_id. Returns zero in case of success and a negative
* error code in case of failure.
*/
@@ -261,7 +269,6 @@
memcpy(vol->name, req->name, vol->name_len + 1);
vol->exclusive = 1;
vol->ubi = ubi;
- ubi->volumes[vol_id] = vol;
spin_unlock(&ubi->volumes_lock);
/*
@@ -345,6 +352,7 @@
spin_lock(&ubi->volumes_lock);
ubi->vol_count += 1;
vol->exclusive = 0;
+ ubi->volumes[vol_id] = vol;
spin_unlock(&ubi->volumes_lock);
paranoid_check_volumes(ubi);
@@ -353,7 +361,7 @@
out_sysfs:
/*
- * We have degistered our device, we should not free the volume*
+ * We have registered our device, we should not free the volume*
* description object in this function in case of an error - it is
* freed by the release function.
*
@@ -373,7 +381,6 @@
spin_lock(&ubi->volumes_lock);
ubi->rsvd_pebs -= vol->reserved_pebs;
ubi->avail_pebs += vol->reserved_pebs;
- ubi->volumes[vol_id] = NULL;
out_unlock:
spin_unlock(&ubi->volumes_lock);
mutex_unlock(&ubi->volumes_mutex);
@@ -407,25 +414,32 @@
return -EROFS;
mutex_lock(&ubi->volumes_mutex);
+ spin_lock(&ubi->volumes_lock);
+ if (vol->ref_count > 1) {
+ /*
+ * The volume is busy, probably someone is reading one of its
+ * sysfs files.
+ */
+ err = -EBUSY;
+ goto out_unlock;
+ }
+ ubi->volumes[vol_id] = NULL;
+ spin_unlock(&ubi->volumes_lock);
+
err = ubi_destroy_gluebi(vol);
if (err)
- goto out;
+ goto out_err;
err = ubi_change_vtbl_record(ubi, vol_id, NULL);
if (err)
- goto out;
+ goto out_err;
for (i = 0; i < vol->reserved_pebs; i++) {
err = ubi_eba_unmap_leb(ubi, vol, i);
if (err)
- goto out;
+ goto out_err;
}
- spin_lock(&ubi->volumes_lock);
- vol->removed = 1;
- ubi->volumes[vol_id] = NULL;
- spin_unlock(&ubi->volumes_lock);
-
kfree(vol->eba_tbl);
vol->eba_tbl = NULL;
cdev_del(&vol->cdev);
@@ -447,7 +461,15 @@
spin_unlock(&ubi->volumes_lock);
paranoid_check_volumes(ubi);
-out:
+ mutex_unlock(&ubi->volumes_mutex);
+ return 0;
+
+out_err:
+ ubi_err("cannot remove volume %d, error %d", vol_id, err);
+ spin_lock(&ubi->volumes_lock);
+ ubi->volumes[vol_id] = vol;
+out_unlock:
+ spin_unlock(&ubi->volumes_lock);
mutex_unlock(&ubi->volumes_mutex);
return err;
}
@@ -494,8 +516,17 @@
for (i = 0; i < reserved_pebs; i++)
new_mapping[i] = UBI_LEB_UNMAPPED;
- /* Reserve physical eraseblocks */
mutex_lock(&ubi->volumes_mutex);
+ spin_lock(&ubi->volumes_lock);
+ if (vol->ref_count > 1) {
+ spin_unlock(&ubi->volumes_lock);
+ err = -EBUSY;
+ goto out_free;
+ }
+ spin_unlock(&ubi->volumes_lock);
+
+
+ /* Reserve physical eraseblocks */
pebs = reserved_pebs - vol->reserved_pebs;
if (pebs > 0) {
spin_lock(&ubi->volumes_lock);
@@ -577,8 +608,8 @@
* @ubi: UBI device description object
* @vol: volume description object
*
- * This function adds an existin volume and initializes all its data
- * structures. Returnes zero in case of success and a negative error code in
+ * This function adds an existing volume and initializes all its data
+ * structures. Returns zero in case of success and a negative error code in
* case of failure.
*/
int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
@@ -588,7 +619,6 @@
dbg_msg("add volume %d", vol_id);
ubi_dbg_dump_vol_info(vol);
- ubi_assert(vol);
/* Register character device for the volume */
cdev_init(&vol->cdev, &ubi_vol_cdev_operations);
@@ -645,11 +675,9 @@
int err;
dbg_msg("free volume %d", vol->vol_id);
- ubi_assert(vol);
- vol->removed = 1;
- err = ubi_destroy_gluebi(vol);
ubi->volumes[vol->vol_id] = NULL;
+ err = ubi_destroy_gluebi(vol);
cdev_del(&vol->cdev);
volume_sysfs_close(vol);
}