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author | Artem Bityutskiy <Artem.Bityutskiy@nokia.com> | 2007-12-17 16:37:26 +0100 |
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committer | Artem Bityutskiy <Artem.Bityutskiy@nokia.com> | 2007-12-26 18:15:17 +0100 |
commit | e73f4459d969bb266f03dd4cbe21bdba8cb2732c (patch) | |
tree | 5af7655da65f2c33f6ea4efdfaa8b0e0670d6aea /drivers/mtd/ubi/build.c | |
parent | UBI: add UBI control device (diff) | |
download | linux-e73f4459d969bb266f03dd4cbe21bdba8cb2732c.tar.xz linux-e73f4459d969bb266f03dd4cbe21bdba8cb2732c.zip |
UBI: add UBI devices reference counting
This is one more step on the way to "removable" UBI devices. It
adds reference counting for UBI devices. Every time a volume on
this device is opened - the device's refcount is increased. It
is also increased if someone is reading any sysfs file of this
UBI device or of one of its volumes.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Diffstat (limited to 'drivers/mtd/ubi/build.c')
-rw-r--r-- | drivers/mtd/ubi/build.c | 142 |
1 files changed, 127 insertions, 15 deletions
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index 3f37b16f8774..a4faf71ee3f2 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -64,9 +64,6 @@ static int mtd_devs = 0; /* MTD devices specification parameters */ static struct mtd_dev_param mtd_dev_param[UBI_MAX_DEVICES]; -/* All UBI devices in system */ -struct ubi_device *ubi_devices[UBI_MAX_DEVICES]; - /* Root UBI "class" object (corresponds to '/<sysfs>/class/ubi/') */ struct class *ubi_class; @@ -83,6 +80,12 @@ static struct miscdevice ubi_ctrl_cdev = { .fops = &ubi_ctrl_cdev_operations, }; +/* All UBI devices in system */ +static struct ubi_device *ubi_devices[UBI_MAX_DEVICES]; + +/* Protects @ubi_devices and @ubi->ref_count */ +static DEFINE_SPINLOCK(ubi_devices_lock); + /* "Show" method for files in '/<sysfs>/class/ubi/' */ static ssize_t ubi_version_show(struct class *class, char *buf) { @@ -118,37 +121,145 @@ static struct device_attribute dev_min_io_size = static struct device_attribute dev_bgt_enabled = __ATTR(bgt_enabled, S_IRUGO, dev_attribute_show, NULL); +/** + * ubi_get_device - get UBI device. + * @ubi_num: UBI device number + * + * This function returns UBI device description object for UBI device number + * @ubi_num, or %NULL if the device does not exist. This function increases the + * device reference count to prevent removal of the device. In other words, the + * device cannot be removed if its reference count is not zero. + */ +struct ubi_device *ubi_get_device(int ubi_num) +{ + struct ubi_device *ubi; + + spin_lock(&ubi_devices_lock); + ubi = ubi_devices[ubi_num]; + if (ubi) { + ubi_assert(ubi->ref_count >= 0); + ubi->ref_count += 1; + get_device(&ubi->dev); + } + spin_unlock(&ubi_devices_lock); + + return ubi; +} + +/** + * ubi_put_device - drop an UBI device reference. + * @ubi: UBI device description object + */ +void ubi_put_device(struct ubi_device *ubi) +{ + spin_lock(&ubi_devices_lock); + ubi->ref_count -= 1; + put_device(&ubi->dev); + spin_unlock(&ubi_devices_lock); +} + +/** + * ubi_get_by_major - get UBI device description object by character device + * major number. + * @major: major number + * + * This function is similar to 'ubi_get_device()', but it searches the device + * by its major number. + */ +struct ubi_device *ubi_get_by_major(int major) +{ + int i; + struct ubi_device *ubi; + + spin_lock(&ubi_devices_lock); + for (i = 0; i < UBI_MAX_DEVICES; i++) { + ubi = ubi_devices[i]; + if (ubi && MAJOR(ubi->cdev.dev) == major) { + ubi_assert(ubi->ref_count >= 0); + ubi->ref_count += 1; + get_device(&ubi->dev); + spin_unlock(&ubi_devices_lock); + return ubi; + } + } + spin_unlock(&ubi_devices_lock); + + return NULL; +} + +/** + * ubi_major2num - get UBI device number by character device major number. + * @major: major number + * + * This function searches UBI device number object by its major number. If UBI + * device was not found, this function returns -ENODEV, othewise the UBI device + * number is returned. + */ +int ubi_major2num(int major) +{ + int i, ubi_num = -ENODEV; + + spin_lock(&ubi_devices_lock); + for (i = 0; i < UBI_MAX_DEVICES; i++) { + struct ubi_device *ubi = ubi_devices[i]; + + if (ubi && MAJOR(ubi->cdev.dev) == major) { + ubi_num = ubi->ubi_num; + break; + } + } + spin_unlock(&ubi_devices_lock); + + return ubi_num; +} + /* "Show" method for files in '/<sysfs>/class/ubi/ubiX/' */ static ssize_t dev_attribute_show(struct device *dev, struct device_attribute *attr, char *buf) { - const struct ubi_device *ubi; + ssize_t ret; + struct ubi_device *ubi; + /* + * The below code looks weird, but it actually makes sense. We get the + * UBI device reference from the contained 'struct ubi_device'. But it + * is unclear if the device was removed or not yet. Indeed, if the + * device was removed before we increased its reference count, + * 'ubi_get_device()' will return -ENODEV and we fail. + * + * Remember, 'struct ubi_device' is freed in the release function, so + * we still can use 'ubi->ubi_num'. + */ ubi = container_of(dev, struct ubi_device, dev); + ubi = ubi_get_device(ubi->ubi_num); + if (!ubi) + return -ENODEV; + if (attr == &dev_eraseblock_size) - return sprintf(buf, "%d\n", ubi->leb_size); + ret = sprintf(buf, "%d\n", ubi->leb_size); else if (attr == &dev_avail_eraseblocks) - return sprintf(buf, "%d\n", ubi->avail_pebs); + ret = sprintf(buf, "%d\n", ubi->avail_pebs); else if (attr == &dev_total_eraseblocks) - return sprintf(buf, "%d\n", ubi->good_peb_count); + ret = sprintf(buf, "%d\n", ubi->good_peb_count); else if (attr == &dev_volumes_count) - return sprintf(buf, "%d\n", ubi->vol_count); + ret = sprintf(buf, "%d\n", ubi->vol_count); else if (attr == &dev_max_ec) - return sprintf(buf, "%d\n", ubi->max_ec); + ret = sprintf(buf, "%d\n", ubi->max_ec); else if (attr == &dev_reserved_for_bad) - return sprintf(buf, "%d\n", ubi->beb_rsvd_pebs); + ret = sprintf(buf, "%d\n", ubi->beb_rsvd_pebs); else if (attr == &dev_bad_peb_count) - return sprintf(buf, "%d\n", ubi->bad_peb_count); + ret = sprintf(buf, "%d\n", ubi->bad_peb_count); else if (attr == &dev_max_vol_count) - return sprintf(buf, "%d\n", ubi->vtbl_slots); + ret = sprintf(buf, "%d\n", ubi->vtbl_slots); else if (attr == &dev_min_io_size) - return sprintf(buf, "%d\n", ubi->min_io_size); + ret = sprintf(buf, "%d\n", ubi->min_io_size); else if (attr == &dev_bgt_enabled) - return sprintf(buf, "%d\n", ubi->thread_enabled); + ret = sprintf(buf, "%d\n", ubi->thread_enabled); else BUG(); - return 0; + ubi_put_device(ubi); + return ret; } /* Fake "release" method for UBI devices */ @@ -670,6 +781,7 @@ static void detach_mtd_dev(struct ubi_device *ubi) int ubi_num = ubi->ubi_num, mtd_num = ubi->mtd->index; dbg_msg("detaching mtd%d from ubi%d", ubi->mtd->index, ubi_num); + ubi_assert(ubi->ref_count == 0); uif_close(ubi); ubi_eba_close(ubi); ubi_wl_close(ubi); |