[PATCH 2/5] UBI: add UBI devices reference counting

Artem Bityutskiy
2007-12-19T13:56:03Z

>From 5f796dcd856305efdc78974681d96b9c06815a13 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Mon, 17 Dec 2007 17:37:26 +0200
Subject: [PATCH] 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>
---
drivers/mtd/ubi/build.c | 142 ++++++++++++++++++++++++++++++++++++++++++-----
drivers/mtd/ubi/cdev.c | 34 +++--------
drivers/mtd/ubi/eba.c | 5 ++
drivers/mtd/ubi/kapi.c | 59 ++++++++++++++------
drivers/mtd/ubi/ubi.h | 9 +++-
drivers/mtd/ubi/vmt.c | 14 +++--
drivers/mtd/ubi/wl.c | 1 +
7 files changed, 201 insertions(+), 63 deletions(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 8d05d96..e60a646 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -63,9 +63,6 @@ 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;

@@ -81,6 +78,12 @@ static int ubi_ctrl_major;
/* Linux device model object corresponding to the control UBI device */
static struct device ubi_ctrl_dev;

+/* 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)
{
@@ -116,37 +119,145 @@ 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 */
@@ -671,6 +782,7 @@ 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);
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index bc900d2..01978b5 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -56,23 +56,6 @@
#endif

/**
- * major_to_device - get UBI device object by character device major number.
- * @major: major number
- *
- * This function returns a pointer to the UBI device object.
- */
-static struct ubi_device *major_to_device(int major)
-{
- int i;
-
- for (i = 0; i < UBI_MAX_DEVICES; i++)
- if (ubi_devices[i] && MAJOR(ubi_devices[i]->cdev.dev) == major)
- return ubi_devices[i];
- BUG();
- return NULL;
-}
-
-/**
* get_exclusive - get exclusive access to an UBI volume.
* @desc: volume descriptor
*
@@ -129,9 +112,11 @@ static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
static int vol_cdev_open(struct inode *inode, struct file *file)
{
struct ubi_volume_desc *desc;
- const struct ubi_device *ubi = major_to_device(imajor(inode));
- int vol_id = iminor(inode) - 1;
- int mode;
+ int vol_id = iminor(inode) - 1, mode, ubi_num;
+
+ ubi_num = ubi_major2num(imajor(inode));
+ if (ubi_num < 0)
+ return ubi_num;

if (file->f_mode & FMODE_WRITE)
mode = UBI_READWRITE;
@@ -140,7 +125,7 @@ static int vol_cdev_open(struct inode *inode, struct file *file)

dbg_msg("open volume %d, mode %d", vol_id, mode);

- desc = ubi_open_volume(ubi->ubi_num, vol_id, mode);
+ desc = ubi_open_volume(ubi_num, vol_id, mode);
if (IS_ERR(desc))
return PTR_ERR(desc);

@@ -586,9 +571,9 @@ static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
if (!capable(CAP_SYS_RESOURCE))
return -EPERM;

- ubi = major_to_device(imajor(inode));
- if (IS_ERR(ubi))
- return PTR_ERR(ubi);
+ ubi = ubi_get_by_major(imajor(inode));
+ if (!ubi)
+ return -ENODEV;

switch (cmd) {
/* Create volume command */
@@ -695,6 +680,7 @@ static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
break;
}

+ ubi_put_device(ubi);
return err;
}

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index deb348d..677d779 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -339,6 +339,7 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
{
int err, pnum, vol_id = vol->vol_id;

+ ubi_assert(ubi->ref_count > 0);
ubi_assert(vol->ref_count > 0);

if (ubi->ro_mode)
@@ -389,6 +390,7 @@ int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
struct ubi_vid_hdr *vid_hdr;
uint32_t uninitialized_var(crc);

+ ubi_assert(ubi->ref_count > 0);
ubi_assert(vol->ref_count > 0);

err = leb_read_lock(ubi, vol_id, lnum);
@@ -614,6 +616,7 @@ int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
int err, pnum, tries = 0, vol_id = vol->vol_id;
struct ubi_vid_hdr *vid_hdr;

+ ubi_assert(ubi->ref_count > 0);
ubi_assert(vol->ref_count > 0);

if (ubi->ro_mode)
@@ -749,6 +752,7 @@ int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
struct ubi_vid_hdr *vid_hdr;
uint32_t crc;

+ ubi_assert(ubi->ref_count > 0);
ubi_assert(vol->ref_count > 0);

if (ubi->ro_mode)
@@ -865,6 +869,7 @@ int ubi_eba_atomic_leb_change(struct ubi_device *ubi, struct ubi_volume *vol,
struct ubi_vid_hdr *vid_hdr;
uint32_t crc;

+ ubi_assert(ubi->ref_count > 0);
ubi_assert(vol->ref_count > 0);

if (ubi->ro_mode)
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index 780c273..4ec3a33 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -30,23 +30,27 @@
* @ubi_num: UBI device number
* @di: the information is stored here
*
- * This function returns %0 in case of success and a %-ENODEV if there is no
- * such UBI device.
+ * This function returns %0 in case of success, %-EINVAL if the UBI device
+ * number is invalid, and %-ENODEV if there is no such UBI device.
*/
int ubi_get_device_info(int ubi_num, struct ubi_device_info *di)
{
- const struct ubi_device *ubi;
+ struct ubi_device *ubi;

- if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES ||
- !ubi_devices[ubi_num])
+ if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
+ return -EINVAL;
+
+ ubi = ubi_get_device(ubi_num);
+ if (!ubi)
return -ENODEV;

- ubi = ubi_devices[ubi_num];
di->ubi_num = ubi->ubi_num;
di->leb_size = ubi->leb_size;
di->min_io_size = ubi->min_io_size;
di->ro_mode = ubi->ro_mode;
di->cdev = ubi->cdev.dev;
+
+ ubi_put_device(ubi);
return 0;
}
EXPORT_SYMBOL_GPL(ubi_get_device_info);
@@ -111,16 +115,23 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
mode != UBI_EXCLUSIVE)
return ERR_PTR(-EINVAL);

- ubi = ubi_devices[ubi_num];
+ /*
+ * First of all, we have to get the UBI device to prevent its removal.
+ */
+ ubi = ubi_get_device(ubi_num);
if (!ubi)
return ERR_PTR(-ENODEV);

- if (vol_id < 0 || vol_id >= ubi->vtbl_slots)
- return ERR_PTR(-EINVAL);
+ if (vol_id < 0 || vol_id >= ubi->vtbl_slots) {
+ err = -EINVAL;
+ goto out_put_ubi;
+ }

desc = kmalloc(sizeof(struct ubi_volume_desc), GFP_KERNEL);
- if (!desc)
- return ERR_PTR(-ENOMEM);
+ if (!desc) {
+ err = -ENOMEM;
+ goto out_put_ubi;
+ }

err = -ENODEV;
if (!try_module_get(THIS_MODULE))
@@ -188,6 +199,8 @@ out_unlock:
module_put(THIS_MODULE);
out_free:
kfree(desc);
+out_put_ubi:
+ ubi_put_device(ubi);
return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(ubi_open_volume);
@@ -205,6 +218,7 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
{
int i, vol_id = -1, len;
struct ubi_device *ubi;
+ struct ubi_volume_desc *ret;

dbg_msg("open volume %s, mode %d", name, mode);

@@ -218,7 +232,7 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
return ERR_PTR(-EINVAL);

- ubi = ubi_devices[ubi_num];
+ ubi = ubi_get_device(ubi_num);
if (!ubi)
return ERR_PTR(-ENODEV);

@@ -234,10 +248,17 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
}
spin_unlock(&ubi->volumes_lock);

- if (vol_id < 0)
- return ERR_PTR(-ENODEV);
+ if (vol_id >= 0)
+ ret = ubi_open_volume(ubi_num, vol_id, mode);
+ else
+ ret = ERR_PTR(-ENODEV);

- return ubi_open_volume(ubi_num, vol_id, mode);
+ /*
+ * We should put the UBI device even in case of success, because
+ * 'ubi_open_volume()' took a reference as well.
+ */
+ ubi_put_device(ubi);
+ return ret;
}
EXPORT_SYMBOL_GPL(ubi_open_volume_nm);

@@ -248,10 +269,11 @@ EXPORT_SYMBOL_GPL(ubi_open_volume_nm);
void ubi_close_volume(struct ubi_volume_desc *desc)
{
struct ubi_volume *vol = desc->vol;
+ struct ubi_device *ubi = vol->ubi;

dbg_msg("close volume %d, mode %d", vol->vol_id, desc->mode);

- spin_lock(&vol->ubi->volumes_lock);
+ spin_lock(&ubi->volumes_lock);
switch (desc->mode) {
case UBI_READONLY:
vol->readers -= 1;
@@ -263,10 +285,11 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
vol->exclusive = 0;
}
vol->ref_count -= 1;
- spin_unlock(&vol->ubi->volumes_lock);
+ spin_unlock(&ubi->volumes_lock);

- put_device(&vol->dev);
kfree(desc);
+ put_device(&vol->dev);
+ ubi_put_device(ubi);
module_put(THIS_MODULE);
}
EXPORT_SYMBOL_GPL(ubi_close_volume);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 28fbb5b..da88abd 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -245,6 +245,7 @@ struct ubi_wl_entry;
* @beb_rsvd_level, @bad_peb_count, @good_peb_count, @vol_count,
* @vol->readers, @vol->writers, @vol->exclusive,
* @vol->ref_count, @vol->mapping and @vol->eba_tbl.
+ * @ref_count: count of references on the UBI device
*
* @rsvd_pebs: count of reserved physical eraseblocks
* @avail_pebs: count of available physical eraseblocks
@@ -325,6 +326,7 @@ struct ubi_device {
int vol_count;
struct ubi_volume *volumes[UBI_MAX_VOLUMES+UBI_INT_VOL_COUNT];
spinlock_t volumes_lock;
+ int ref_count;

int rsvd_pebs;
int avail_pebs;
@@ -401,7 +403,6 @@ extern struct kmem_cache *ubi_wl_entry_slab;
extern struct file_operations ubi_ctrl_cdev_operations;
extern struct file_operations ubi_cdev_operations;
extern struct file_operations ubi_vol_cdev_operations;
-extern struct ubi_device *ubi_devices[];
extern struct class *ubi_class;

/* vtbl.c */
@@ -479,6 +480,12 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
struct ubi_vid_hdr *vid_hdr);

+/* build.c */
+struct ubi_device *ubi_get_device(int ubi_num);
+void ubi_put_device(struct ubi_device *ubi);
+struct ubi_device *ubi_get_by_major(int major);
+int ubi_major2num(int major);
+
/*
* ubi_rb_for_each_entry - walk an RB-tree.
* @rb: a pointer to type 'struct rb_node' to to use as a loop counter
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 3ed63dc..42d3dd7 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -71,11 +71,16 @@ static ssize_t vol_attribute_show(struct device *dev,
{
int ret;
struct ubi_volume *vol = container_of(dev, struct ubi_volume, dev);
- struct ubi_device *ubi = vol->ubi;
+ struct ubi_device *ubi;
+
+ ubi = ubi_get_device(vol->ubi->ubi_num);
+ if (!ubi)
+ return -ENODEV;

spin_lock(&ubi->volumes_lock);
if (!ubi->volumes[vol->vol_id]) {
spin_unlock(&ubi->volumes_lock);
+ ubi_put_device(ubi);
return -ENODEV;
}
/* Take a reference to prevent volume removal */
@@ -108,10 +113,12 @@ static ssize_t vol_attribute_show(struct device *dev,
/* This must be a bug */
ret = -EINVAL;

+ /* We've done the operation, drop volume and UBI device references */
spin_lock(&ubi->volumes_lock);
vol->ref_count -= 1;
ubi_assert(vol->ref_count >= 0);
spin_unlock(&ubi->volumes_lock);
+ ubi_put_device(ubi);
return ret;
}

@@ -260,6 +267,7 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
}
ubi->avail_pebs -= vol->reserved_pebs;
ubi->rsvd_pebs += vol->reserved_pebs;
+ spin_unlock(&ubi->volumes_lock);

vol->vol_id = vol_id;
vol->alignment = req->alignment;
@@ -267,9 +275,7 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
vol->vol_type = req->vol_type;
vol->name_len = req->name_len;
memcpy(vol->name, req->name, vol->name_len + 1);
- vol->exclusive = 1;
vol->ubi = ubi;
- spin_unlock(&ubi->volumes_lock);

/*
* Finish all pending erases because there may be some LEBs belonging
@@ -350,8 +356,6 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
goto out_sysfs;

spin_lock(&ubi->volumes_lock);
- ubi->vol_count += 1;
- vol->exclusive = 0;
ubi->volumes[vol_id] = vol;
spin_unlock(&ubi->volumes_lock);

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index f90416a..0dc7dc8 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1246,6 +1246,7 @@ int ubi_wl_flush(struct ubi_device *ubi)
* Make sure all the works which have been done in parallel are
* finished.
*/
+ ubi_assert(ubi->ref_count > 0);
down_write(&ubi->work_sem);
up_write(&ubi->work_sem);

--
1.5.3.4