[PATCH 1/1] ubi: Introduce block devices for UBI volumes

Richard Weinberger richard.weinberger at gmail.com
Sat Feb 8 16:37:19 EST 2014


On Wed, Jan 29, 2014 at 9:38 PM, Ezequiel Garcia
<ezequiel.garcia at free-electrons.com> wrote:
> Block device emulation on top of ubi volumes with cached read/write support.
> Both the cached access and the write support are selectable at compile time.
>
> Given UBI takes care of wear leveling and bad block management it's possible
> to add a thin layer to enable block device access to UBI volumes.
> This allows to use a block-oriented filesystem on a flash device.
>
> In a similar fashion to mtdblock, a 1-LEB size cache has been
> implemented. However, very memory-constrained systems can choose to
> disable the cache and save the 1-LEB byte allocation.
>
> If write support is enabled, the flash device will be written when the cache
> is flushed. The following events trigger this:
> * block device release (detach)
> * different than cached leb is accessed
> * io-barrier is received through a REQ_FLUSH request
>
> Despite this efforts, it's very important to remember that regular
> block-oriented filesystems have no care at all about wear leveling;
> they will access the block device randomly, only caring for performance.
> Therefore, write support should be selected only for development and
> with extreme caution.
>
> The cache is 1-LEB bytes, vmalloced at open() and freed at release();
> in addition, each block device has a workqueue associated.
>
> Block devices are created upon user request through new ioctls:
> UBI_IOCVOLATTBLK to attach and UBI_IOCVOLDETBLK to detach.
> Also, a new UBI module parameter is added 'ubi.block'. This parameter is
> needed in order to attach a block device on boot-up time, allowing to
> mount the rootfs on a ubiblock device.
> For instance, you could have these kernel parameters:
>
>   ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0
>
> Or, if you compile ubi as a module:
>
>   $ modprobe ubi mtd=/dev/mtd5 block=/dev/ubi0_0
>
> Cc: Artem Bityutskiy <dedekind1 at gmail.com>
> Cc: David Woodhouse <dwmw2 at infradead.org>
> Cc: Brian Norris <computersforpeace at gmail.com>
> Cc: Michael Opdenacker <michael.opdenacker at free-electrons.com>
> Cc: Tim Bird <tim.bird at am.sony.com>
> Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
> Cc: Mike Frysinger <vapier at gentoo.org>
> Cc: Piergiorgio Beruto <piergiorgio.beruto at gmail.com>
> Cc: Willy Tarreau <w at 1wt.eu>
> Signed-off-by: Ezequiel Garcia <ezequiel.garcia at free-electrons.com>
> ---
>  drivers/mtd/ubi/Kconfig     |  42 +++
>  drivers/mtd/ubi/Makefile    |   1 +
>  drivers/mtd/ubi/block.c     | 899 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/mtd/ubi/build.c     |   5 +
>  drivers/mtd/ubi/cdev.c      |  20 +
>  drivers/mtd/ubi/ubi.h       |  14 +
>  include/uapi/mtd/ubi-user.h |  11 +
>  7 files changed, 992 insertions(+)
>  create mode 100644 drivers/mtd/ubi/block.c
>
> diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
> index 36663af..2893775 100644
> --- a/drivers/mtd/ubi/Kconfig
> +++ b/drivers/mtd/ubi/Kconfig
> @@ -87,4 +87,46 @@ config MTD_UBI_GLUEBI
>            work on top of UBI. Do not enable this unless you use legacy
>            software.
>
> +config MTD_UBI_BLOCK
> +       bool "Block device access to UBI volumes"
> +       default n
> +       help
> +          Since UBI already takes care of eraseblock wear leveling
> +          and bad block handling, it's possible to implement a block
> +          device on top of it and therefore mount regular filesystems
> +          (i.e. not flash-oriented, as ext4).
> +          In other words, this is a software flash translation layer.
> +
> +          This can be particularly interesting to allow mounting a read-only
> +          filesystem, such as squashfs, on a NAND device.
> +
> +          When selected, this feature will be built-in the ubi module
> +          and block devices will be able to be created and removed using
> +          the userspace 'ubiblkvol' tool (provided mtd-utils).
> +
> +          If in doubt, say "N".
> +
> +config MTD_UBI_BLOCK_CACHED
> +       bool "Enable cached UBI block access"
> +       default y
> +       depends on MTD_UBI_BLOCK
> +       help
> +          In order to reduce flash device access, this option enables a 1-LEB
> +          sized cache. For read-only access this can be an overkill, given
> +          filesystems most likely implement their own caching policies.
> +          Moreover, since a LEB can be as large as ~1 MiB, memory-constrained
> +          platforms can choose to disable this.
> +
> +config MTD_UBI_BLOCK_WRITE_SUPPORT
> +       bool "Enable write support (DANGEROUS)"
> +       default n
> +       depends on MTD_UBI_BLOCK
> +       select MTD_UBI_BLOCK_CACHED
> +       help
> +          This is a *very* dangerous feature. Using a regular block-oriented
> +          filesystem might impact heavily on a flash device wear.
> +          Use with extreme caution.
> +
> +          If in doubt, say "N".

I really vote for dropping write support at all.

>  endif # MTD_UBI
> diff --git a/drivers/mtd/ubi/Makefile b/drivers/mtd/ubi/Makefile
> index b46b0c97..4e3c3d7 100644
> --- a/drivers/mtd/ubi/Makefile
> +++ b/drivers/mtd/ubi/Makefile
> @@ -3,5 +3,6 @@ obj-$(CONFIG_MTD_UBI) += ubi.o
>  ubi-y += vtbl.o vmt.o upd.o build.o cdev.o kapi.o eba.o io.o wl.o attach.o
>  ubi-y += misc.o debug.o
>  ubi-$(CONFIG_MTD_UBI_FASTMAP) += fastmap.o
> +ubi-$(CONFIG_MTD_UBI_BLOCK) += block.o
>
>  obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
> diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
> new file mode 100644
> index 0000000..6a7dc00
> --- /dev/null
> +++ b/drivers/mtd/ubi/block.c
> @@ -0,0 +1,899 @@
> +/*
> + * Copyright (c) 2014 Ezequiel Garcia
> + * Copyright (c) 2011 Free Electrons
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation, version 2.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
> + * the GNU General Public License for more details.
> + *
> + * A block implementation on UBI volume
> + * ------------------------------------
> + *
> + * How to use this? A bunch of examples worth a thousand words:
> + *
> + * If you want to attach a block device on bootup time, e.g. in order
> + * to mount the rootfs on such a block device:
> + *
> + * Using the UBI volume path:
> + *  ubi.block=/dev/ubi0_0
> + *
> + * Using the UBI device, and the volume name:
> + *  ubi.block=0,rootfs
> + *
> + * Using both UBI device number and UBI volume number:
> + *  ubi.block=0,0
> + *
> + * In this case you would have such kernel parameters:
> + *  ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0
> + *
> + * Of course, if you compile ubi as a module you can use this
> + * parameter on module insertion time:
> + *  modprobe ubi mtd=/dev/mtd5 block=/dev/ubi0_0
> + *
> + * For runtime block attaching/detaching, see mtd-utils' ubiblkvol tool.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
> +#include <linux/mtd/ubi.h>
> +#include <linux/workqueue.h>
> +#include <linux/blkdev.h>
> +#include <linux/hdreg.h>
> +
> +#include "ubi-media.h"
> +#include "ubi.h"
> +
> +/* Maximum number of supported devices */
> +#define UBIBLOCK_MAX_DEVICES 32
> +
> +/* Maximum length of the 'block=' parameter */
> +#define UBIBLOCK_PARAM_LEN 63
> +
> +/* Maximum number of comma-separated items in the 'block=' parameter */
> +#define UBIBLOCK_PARAM_COUNT 2
> +
> +struct ubiblock_param {
> +       int ubi_num;
> +       int vol_id;
> +       char name[UBIBLOCK_PARAM_LEN+1];
> +};
> +
> +/* Numbers of elements set in the @ubiblock_param array */
> +static int ubiblock_devs __initdata;
> +
> +/* MTD devices specification parameters */
> +static struct ubiblock_param ubiblock_param[UBIBLOCK_MAX_DEVICES] __initdata;
> +
> +struct ubiblock_cache {
> +       char *buffer;
> +       enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } state;
> +       int leb_num;
> +};
> +
> +struct ubiblock {
> +       struct ubi_volume_desc *desc;
> +       struct ubi_volume_info *vi;
> +       int ubi_num;
> +       int vol_id;
> +       int refcnt;
> +
> +       struct gendisk *gd;
> +       struct request_queue *rq;
> +
> +       struct workqueue_struct *wq;
> +       struct work_struct work;
> +
> +       struct mutex vol_mutex;
> +       spinlock_t queue_lock;
> +       struct list_head list;
> +
> +       int leb_size;
> +#ifdef CONFIG_MTD_UBI_BLOCK_CACHED
> +       struct ubiblock_cache cache;
> +#endif
> +};
> +
> +/* Linked list of all ubiblock instances */
> +static LIST_HEAD(ubiblock_devices);
> +static DEFINE_MUTEX(devices_mutex);
> +static int ubiblock_major;
> +
> +/* Ugh! this parameter parsing code is awful */
> +static int __init ubiblock_set_param(const char *val,
> +                                    const struct kernel_param *kp)
> +{
> +       int i, ret;
> +       size_t len;
> +       struct ubiblock_param *param;
> +       char buf[UBIBLOCK_PARAM_LEN];
> +       char *pbuf = &buf[0];
> +       char *tokens[UBIBLOCK_PARAM_COUNT];
> +
> +       if (!val)
> +               return -EINVAL;
> +
> +       len = strnlen(val, UBIBLOCK_PARAM_LEN);
> +       if (len == 0) {
> +               ubi_warn("block: empty 'block=' parameter - ignored\n");
> +               return 0;
> +       }
> +
> +       if (len == UBIBLOCK_PARAM_LEN) {
> +               ubi_err("block: parameter \"%s\" is too long, max. is %d\n",
> +                       val, UBIBLOCK_PARAM_LEN);
> +               return -EINVAL;
> +       }
> +
> +       strcpy(buf, val);
> +
> +       /* Get rid of the final newline */
> +       if (buf[len - 1] == '\n')
> +               buf[len - 1] = '\0';
> +
> +       for (i = 0; i < UBIBLOCK_PARAM_COUNT; i++)
> +               tokens[i] = strsep(&pbuf, ",");
> +
> +       param = &ubiblock_param[ubiblock_devs];
> +       if (tokens[1]) {
> +               /* Two parameters: can be 'ubi, vol_id' or 'ubi, vol_name' */
> +               ret = kstrtoint(tokens[0], 10, &param->ubi_num);
> +               if (ret < 0)
> +                       return -EINVAL;
> +
> +               /* Second param can be a number or a name */
> +               ret = kstrtoint(tokens[1], 10, &param->vol_id);
> +               if (ret < 0) {
> +                       param->vol_id = -1;
> +                       strcpy(param->name, tokens[1]);
> +               }
> +
> +       } else {
> +               /* One parameter: must be device path */
> +               strcpy(param->name, tokens[0]);
> +               param->ubi_num = -1;
> +               param->vol_id = -1;
> +       }
> +
> +       ubiblock_devs++;
> +
> +       return 0;
> +}
> +
> +static const struct kernel_param_ops ubiblock_param_ops = {
> +       .set    = ubiblock_set_param,
> +};
> +module_param_cb(block, &ubiblock_param_ops, NULL, 0);
> +MODULE_PARM_DESC(block, "Attach block devices to UBI volumes. Parameter format: block=<path|dev,num|dev,name>.\n"
> +                       "Multiple \"block\" parameters may be specified.\n"
> +                       "UBI volumes may be specified by their number, name, or path to the device node.\n"
> +                       "Examples\n"
> +                       "Using the UBI volume path:\n"
> +                       "ubi.block=/dev/ubi0_0\n"
> +                       "Using the UBI device, and the volume name:\n"
> +                       "ubi.block=0,rootfs\n"
> +                       "Using both UBI device number and UBI volume number:\n"
> +                       "ubi.block=0,0\n");
> +
> +static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
> +{
> +       struct ubiblock *dev;
> +
> +       list_for_each_entry(dev, &ubiblock_devices, list)
> +               if (dev->ubi_num == ubi_num && dev->vol_id == vol_id)
> +                       return dev;
> +       return NULL;
> +}
> +
> +#ifdef CONFIG_MTD_UBI_BLOCK_CACHED
> +static void ubiblock_clean_cache(struct ubiblock *dev)
> +{
> +       dev->cache.leb_num = -1;
> +       dev->cache.state = STATE_EMPTY;
> +}
> +
> +static void ubiblock_free_cache(struct ubiblock *dev)
> +{
> +       dev->cache.leb_num = -1;
> +       dev->cache.state = STATE_EMPTY;
> +       vfree(dev->cache.buffer);
> +       dev->cache.buffer = NULL;
> +}
> +
> +static int ubiblock_alloc_cache(struct ubiblock *dev)
> +{
> +       dev->cache.state = STATE_EMPTY;
> +       dev->cache.leb_num = -1;
> +       dev->cache.buffer = vmalloc(dev->leb_size);
> +       if (!dev->cache.buffer)
> +               return -ENOMEM;
> +       return 0;
> +}
> +
> +static bool leb_in_cache(struct ubiblock_cache *cache, int leb_num)
> +{
> +       return cache->leb_num == leb_num;
> +}
> +
> +static int ubiblock_fill_cache(struct ubiblock *dev, int leb_num,
> +                              struct ubiblock_cache *cache)
> +{
> +       int ret;
> +
> +       /* Warn if we fill cache while being dirty */
> +       WARN_ON(cache->state == STATE_DIRTY);
> +
> +       cache->leb_num = leb_num;
> +       cache->state = STATE_CLEAN;
> +
> +       ret = ubi_read(dev->desc, leb_num, cache->buffer, 0,
> +                      dev->leb_size);
> +       if (ret) {
> +               ubi_err("%s ubi_read error %d", dev->gd->disk_name, ret);
> +               return ret;
> +       }

If read fails we still end up with a valid cache entry?
Please set STATE_CLEAN only after a successful read.

> +       return 0;
> +}
> +
> +static int ubiblock_read_to_buf(struct ubiblock *dev, char *buffer,
> +                               int leb, int offset, int len)
> +{
> +       int ret;
> +       char *cache_buffer;
> +       /*
> +        * First try in cache, if it's not there load this leb.
> +        * Note that reading never flushes to disk!
> +        */
> +       if (leb_in_cache(&dev->cache, leb)) {
> +               cache_buffer = dev->cache.buffer;
> +       } else {
> +               /* Leb is not in cache: fill it! */
> +               ret = ubiblock_fill_cache(dev, leb, &dev->cache);
> +               if (ret)
> +                       return ret;
> +               cache_buffer = dev->cache.buffer;
> +       }
> +       memcpy(buffer, cache_buffer + offset, len);
> +       return 0;
> +}
> +#else
> +static inline void ubiblock_clean_cache(struct ubiblock *dev) {}
> +
> +static inline void ubiblock_free_cache(struct ubiblock *dev) {}
> +
> +static inline int ubiblock_alloc_cache(struct ubiblock *dev)
> +{
> +       return 0;
> +}
> +
> +static int ubiblock_read_to_buf(struct ubiblock *dev, char *buffer,
> +                               int leb, int offset, int len)
> +{
> +       int ret;
> +
> +       ret = ubi_read(dev->desc, leb, buffer, offset, len);
> +       if (ret) {
> +               ubi_err("%s ubi_read error %d",
> +                       dev->gd->disk_name, ret);
> +               return ret;
> +       }
> +       return 0;
> +}
> +#endif /* CONFIG_MTD_UBI_BLOCK_CACHED */
> +
> +#ifdef CONFIG_MTD_UBI_BLOCK_WRITE_SUPPORT
> +static int ubiblock_flush(struct ubiblock *dev, bool sync)
> +{
> +       struct ubiblock_cache *cache = &dev->cache;
> +       int ret = 0;
> +
> +       if (cache->state != STATE_DIRTY)
> +               return 0;
> +
> +       /*
> +        * mtdblock sets STATE_EMPTY, arguing that it prevents the
> +        * underlying media to get changed without notice.
> +        * I'm not fully convinced, so I just put STATE_CLEAN.
> +        */
> +       cache->state = STATE_CLEAN;
> +
> +       /* Atomically change leb with buffer contents */
> +       ret = ubi_leb_change(dev->desc, cache->leb_num,
> +                            cache->buffer, dev->leb_size);
> +       if (ret) {
> +               ubi_err("%s ubi_leb_change error %d",
> +                       dev->gd->disk_name, ret);
> +               return ret;
> +       }
> +
> +       /* Sync ubi device when device is released and on block flush ioctl */
> +       if (sync)
> +               ret = ubi_sync(dev->ubi_num);
> +
> +       return ret;
> +}
> +
> +static int ubiblock_write(struct ubiblock *dev, const char *buffer,
> +                         int pos, int len)
> +{
> +       int leb, offset, ret;
> +       int bytes_left = len;
> +       int to_write = len;
> +       struct ubiblock_cache *cache = &dev->cache;
> +
> +       /* Get (leb:offset) address to write */
> +       leb = pos / dev->leb_size;
> +       offset = pos % dev->leb_size;
> +
> +       while (bytes_left) {
> +               /*
> +                * We can only write one leb at a time.
> +                * Therefore if the write length is larger than
> +                * one leb size, we split the operation.
> +                */
> +               if (offset + to_write > dev->leb_size)
> +                       to_write = dev->leb_size - offset;
> +
> +               /*
> +                * If leb is not in cache, we flush current cached
> +                * leb to disk. Cache contents will be filled by reading device.
> +                */
> +               if (!leb_in_cache(cache, leb)) {
> +
> +                       ret = ubiblock_flush(dev, false);
> +                       if (ret)
> +                               return ret;
> +
> +                       ret = ubiblock_fill_cache(dev, leb, cache);
> +                       if (ret)
> +                               return ret;
> +               }
> +
> +               memcpy(cache->buffer + offset, buffer, to_write);
> +
> +               /* This is the only place where we dirt the cache */
> +               cache->state = STATE_DIRTY;
> +
> +               buffer += to_write;
> +               bytes_left -= to_write;
> +               to_write = bytes_left;
> +               offset = 0;
> +               leb++;
> +       }
> +       return 0;
> +}
> +#else
> +static int ubiblock_flush(struct ubiblock *dev, bool sync)
> +{
> +       return -EPERM;
> +}
> +
> +static int ubiblock_write(struct ubiblock *dev, const char *buffer,
> +                         int pos, int len)
> +{
> +       return -EPERM;
> +}
> +#endif /* CONFIG_MTD_UBI_BLOCK_WRITE_SUPPORT */
> +
> +static int ubiblock_read(struct ubiblock *dev, char *buffer, int pos, int len)
> +{
> +       int leb, offset, ret;
> +       int bytes_left = len;
> +       int to_read = len;
> +
> +       /* Get leb:offset address to read from */
> +       leb = pos / dev->leb_size;
> +       offset = pos % dev->leb_size;
> +
> +       while (bytes_left) {
> +
> +               /*
> +                * We can only read one leb at a time.
> +                * Therefore if the read length is larger than
> +                * one leb size, we split the operation.
> +                */
> +               if (offset + to_read > dev->leb_size)
> +                       to_read = dev->leb_size - offset;
> +
> +               ret = ubiblock_read_to_buf(dev, buffer, leb, offset, to_read);
> +               if (ret)
> +                       return ret;
> +
> +               buffer += to_read;
> +               bytes_left -= to_read;
> +               to_read = bytes_left;
> +               leb++;
> +               offset = 0;
> +       }
> +       return 0;
> +}
> +
> +static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
> +{
> +       int pos, len;
> +
> +       if (req->cmd_flags & REQ_FLUSH)
> +               return ubiblock_flush(dev, true);
> +
> +       if (req->cmd_type != REQ_TYPE_FS)
> +               return -EIO;
> +
> +       if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
> +           get_capacity(req->rq_disk))
> +               return -EIO;
> +
> +       pos = blk_rq_pos(req) << 9;
> +       len = blk_rq_cur_bytes(req);
> +
> +       switch (rq_data_dir(req)) {
> +       case READ:
> +               return ubiblock_read(dev, req->buffer, pos, len);
> +       case WRITE:
> +               return ubiblock_write(dev, req->buffer, pos, len);
> +       default:
> +               return -EIO;
> +       }
> +
> +       return 0;
> +}
> +
> +static void ubiblock_do_work(struct work_struct *work)
> +{
> +       struct ubiblock *dev =
> +               container_of(work, struct ubiblock, work);
> +       struct request_queue *rq = dev->rq;
> +       struct request *req;
> +       int res;
> +
> +       spin_lock_irq(rq->queue_lock);
> +
> +       req = blk_fetch_request(rq);
> +       while (req) {
> +
> +               spin_unlock_irq(rq->queue_lock);
> +
> +               mutex_lock(&dev->vol_mutex);
> +               res = do_ubiblock_request(dev, req);
> +               mutex_unlock(&dev->vol_mutex);

This means that you can never do parallel IO?

> +
> +               spin_lock_irq(rq->queue_lock);
> +
> +               /*
> +                * If we're done with this request,
> +                * we need to fetch a new one
> +                */
> +               if (!__blk_end_request_cur(req, res))
> +                       req = blk_fetch_request(rq);
> +       }
> +
> +       spin_unlock_irq(rq->queue_lock);
> +}
> +
> +static void ubiblock_request(struct request_queue *rq)
> +{
> +       struct ubiblock *dev;
> +       struct request *req;
> +
> +       dev = rq->queuedata;
> +
> +       if (!dev)
> +               while ((req = blk_fetch_request(rq)) != NULL)
> +                       __blk_end_request_all(req, -ENODEV);
> +       else
> +               queue_work(dev->wq, &dev->work);
> +}
> +
> +static int ubiblock_open(struct block_device *bdev, fmode_t mode)
> +{
> +       struct ubiblock *dev = bdev->bd_disk->private_data;
> +       int ubi_mode = UBI_READONLY;
> +       int ret;
> +#ifdef CONFIG_MTD_UBI_BLOCK_WRITE_SUPPORT
> +       const bool allow_write = true;
> +#else
> +       const bool allow_write = false;
> +#endif
> +
> +       mutex_lock(&dev->vol_mutex);
> +       if (dev->refcnt > 0) {
> +               /*
> +                * The volume is already opened,
> +                * just increase the reference counter
> +                *
> +                * If the first user has oppened this as read-only,
> +                * we don't allow to open as read-write.
> +                * This is the simplest solution. A better one would
> +                * be to re-open the volume as writable.
> +                */
> +               if ((mode & FMODE_WRITE) &&
> +                   (dev->desc->mode != UBI_READWRITE)) {
> +                       ret = -EBUSY;
> +                       goto out_unlock;
> +               }
> +               goto out_done;
> +       }
> +
> +       if (allow_write) {
> +               if (mode & FMODE_WRITE)
> +                       ubi_mode = UBI_READWRITE;
> +       } else {
> +               if (mode & FMODE_WRITE) {
> +                       ret = -EPERM;
> +                       goto out_unlock;
> +               }
> +       }
> +
> +       dev->desc = ubi_open_volume(dev->ubi_num, dev->vol_id, ubi_mode);
> +       if (IS_ERR(dev->desc)) {
> +               ubi_err("%s failed to open ubi volume %d_%d",
> +                       dev->gd->disk_name, dev->ubi_num, dev->vol_id);
> +
> +               ret = PTR_ERR(dev->desc);
> +               dev->desc = NULL;
> +               goto out_unlock;
> +       }
> +
> +       dev->vi = kzalloc(sizeof(struct ubi_volume_info), GFP_KERNEL);
> +       if (!dev->vi) {
> +               ret = -ENOMEM;
> +               goto out_close;
> +       }
> +       ubi_get_volume_info(dev->desc, dev->vi);
> +       dev->leb_size = dev->vi->usable_leb_size;
> +
> +       ret = ubiblock_alloc_cache(dev);
> +       if (ret)
> +               goto out_free;
> +out_done:
> +       dev->refcnt++;
> +       mutex_unlock(&dev->vol_mutex);
> +       return 0;
> +
> +out_free:
> +       kfree(dev->vi);
> +out_close:
> +       ubi_close_volume(dev->desc);
> +       dev->desc = NULL;
> +out_unlock:
> +       mutex_unlock(&dev->vol_mutex);
> +       return ret;
> +}
> +
> +static void ubiblock_release(struct gendisk *gd, fmode_t mode)
> +{
> +       struct ubiblock *dev = gd->private_data;
> +
> +       mutex_lock(&dev->vol_mutex);
> +
> +       dev->refcnt--;
> +       if (dev->refcnt == 0) {
> +               ubiblock_flush(dev, true);
> +               ubiblock_free_cache(dev);
> +
> +               kfree(dev->vi);
> +               ubi_close_volume(dev->desc);
> +
> +               dev->vi = NULL;
> +               dev->desc = NULL;
> +       }
> +
> +       mutex_unlock(&dev->vol_mutex);
> +}
> +
> +static int ubiblock_ioctl(struct block_device *bdev, fmode_t mode,
> +                             unsigned int cmd, unsigned long arg)
> +{
> +       struct ubiblock *dev = bdev->bd_disk->private_data;
> +       int ret = -ENXIO;
> +
> +       if (!dev)
> +               return ret;
> +
> +       mutex_lock(&dev->vol_mutex);
> +
> +       /* I can't get this to get called. What's going on? */
> +       switch (cmd) {
> +       case BLKFLSBUF:
> +               ret = ubiblock_flush(dev, true);
> +               break;
> +       default:
> +               ret = -ENOTTY;
> +       }
> +
> +       mutex_unlock(&dev->vol_mutex);
> +       return ret;
> +}
> +
> +static int ubiblock_getgeo(struct block_device *bdev, struct hd_geometry *geo)
> +{
> +       /* Some tools might require this information */
> +       geo->heads = 1;
> +       geo->cylinders = 1;
> +       geo->sectors = get_capacity(bdev->bd_disk);
> +       geo->start = 0;
> +       return 0;
> +}
> +
> +static const struct block_device_operations ubiblock_ops = {
> +       .owner = THIS_MODULE,
> +       .open = ubiblock_open,
> +       .release = ubiblock_release,
> +       .ioctl = ubiblock_ioctl,
> +       .getgeo = ubiblock_getgeo,
> +};
> +
> +int ubiblock_add(struct ubi_volume_info *vi)
> +{
> +       struct ubiblock *dev;
> +       struct gendisk *gd;
> +       int disk_capacity;
> +       int ret;
> +
> +       /* Check that the volume isn't already handled */
> +       mutex_lock(&devices_mutex);
> +       if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {
> +               mutex_unlock(&devices_mutex);
> +               return -EEXIST;
> +       }
> +       mutex_unlock(&devices_mutex);
> +
> +       dev = kzalloc(sizeof(struct ubiblock), GFP_KERNEL);
> +       if (!dev)
> +               return -ENOMEM;
> +
> +       mutex_init(&dev->vol_mutex);
> +
> +       dev->ubi_num = vi->ubi_num;
> +       dev->vol_id = vi->vol_id;
> +
> +       ubiblock_clean_cache(dev);
> +
> +       /* Initialize the gendisk of this ubiblock device */
> +       gd = alloc_disk(1);
> +       if (!gd) {
> +               ubi_err("block: alloc_disk failed");
> +               ret = -ENODEV;
> +               goto out_free_dev;
> +       }
> +
> +       gd->fops = &ubiblock_ops;
> +       gd->major = ubiblock_major;
> +       gd->first_minor = dev->ubi_num * UBI_MAX_VOLUMES + dev->vol_id;
> +       gd->private_data = dev;
> +       sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);
> +       disk_capacity = (vi->size * vi->usable_leb_size) >> 9;
> +       set_capacity(gd, disk_capacity);
> +       dev->gd = gd;
> +
> +       spin_lock_init(&dev->queue_lock);
> +       dev->rq = blk_init_queue(ubiblock_request, &dev->queue_lock);
> +       if (!dev->rq) {
> +               ubi_err("block: blk_init_queue failed");
> +               ret = -ENODEV;
> +               goto out_put_disk;
> +       }
> +
> +       dev->rq->queuedata = dev;
> +       dev->gd->queue = dev->rq;
> +
> +       blk_queue_flush(dev->rq, REQ_FLUSH);
> +
> +       /*
> +        * Create one workqueue per volume (per registered block device).
> +        * Rembember workqueues are cheap, they're not threads.
> +        */
> +       dev->wq = alloc_workqueue(gd->disk_name, 0, 0);
> +       if (!dev->wq)
> +               goto out_free_queue;
> +       INIT_WORK(&dev->work, ubiblock_do_work);
> +
> +       mutex_lock(&devices_mutex);
> +       list_add_tail(&dev->list, &ubiblock_devices);
> +       mutex_unlock(&devices_mutex);
> +
> +       /* Must be the last step: anyone can call file ops from now on */
> +       add_disk(dev->gd);
> +
> +       ubi_msg("%s created from ubi%d:%d(%s)",
> +               dev->gd->disk_name, dev->ubi_num, dev->vol_id, vi->name);
> +
> +       return 0;
> +
> +out_free_queue:
> +       blk_cleanup_queue(dev->rq);
> +out_put_disk:
> +       put_disk(dev->gd);
> +out_free_dev:
> +       kfree(dev);
> +
> +       return ret;
> +}
> +
> +static void ubiblock_cleanup(struct ubiblock *dev)
> +{
> +       del_gendisk(dev->gd);
> +       blk_cleanup_queue(dev->rq);
> +       ubi_msg("%s released", dev->gd->disk_name);
> +       put_disk(dev->gd);
> +}
> +
> +int ubiblock_del(struct ubi_volume_info *vi)
> +{
> +       struct ubiblock *dev;
> +
> +       mutex_lock(&devices_mutex);
> +       dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
> +       if (!dev) {
> +               mutex_unlock(&devices_mutex);
> +               return -ENODEV;
> +       }
> +
> +       /* Found a device, let's lock it so we can check if it's busy */
> +       mutex_lock(&dev->vol_mutex);
> +
> +       if (dev->refcnt > 0) {
> +               mutex_unlock(&dev->vol_mutex);
> +               mutex_unlock(&devices_mutex);
> +               return -EBUSY;
> +       }
> +
> +       /* Remove from device list */
> +       list_del(&dev->list);
> +       mutex_unlock(&devices_mutex);
> +
> +       /* Flush pending work and stop this workqueue */
> +       destroy_workqueue(dev->wq);
> +
> +       ubiblock_cleanup(dev);
> +       mutex_unlock(&dev->vol_mutex);
> +       kfree(dev);
> +       return 0;
> +}
> +
> +static void ubiblock_resize(struct ubi_volume_info *vi)
> +{
> +       struct ubiblock *dev;
> +       int disk_capacity;
> +
> +       /*
> +        * Need to lock the device list until we stop using the device,
> +        * otherwise the device struct might get released in ubiblock_del().
> +        */
> +       mutex_lock(&devices_mutex);
> +       dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
> +       if (!dev) {
> +               mutex_unlock(&devices_mutex);
> +               return;
> +       }
> +
> +       mutex_lock(&dev->vol_mutex);
> +       disk_capacity = (vi->size * vi->usable_leb_size) >> 9;
> +       set_capacity(dev->gd, disk_capacity);
> +       ubi_msg("%s resized to %d LEBs", dev->gd->disk_name, vi->size);
> +       mutex_unlock(&dev->vol_mutex);
> +       mutex_unlock(&devices_mutex);
> +}
> +
> +static int ubiblock_notify(struct notifier_block *nb,
> +                        unsigned long notification_type, void *ns_ptr)
> +{
> +       struct ubi_notification *nt = ns_ptr;
> +
> +       switch (notification_type) {
> +       case UBI_VOLUME_ADDED:
> +               /*
> +                * We want to enforce explicit block device attaching for
> +                * volumes; so when a volume is added we do nothing.
> +                */
> +               break;
> +       case UBI_VOLUME_REMOVED:
> +               ubiblock_del(&nt->vi);
> +               break;
> +       case UBI_VOLUME_RESIZED:
> +               ubiblock_resize(&nt->vi);
> +               break;
> +       default:
> +               break;
> +       }
> +       return NOTIFY_OK;
> +}
> +
> +static struct notifier_block ubiblock_notifier = {
> +       .notifier_call = ubiblock_notify,
> +};
> +
> +static struct ubi_volume_desc * __init
> +open_volume_desc(const char *name, int ubi_num, int vol_id)
> +{
> +       if (ubi_num == -1)
> +               /* No ubi num, name must be a vol device path */
> +               return ubi_open_volume_path(name, UBI_READONLY);
> +       else if (vol_id == -1)
> +               /* No vol_id, must be vol_name */
> +               return ubi_open_volume_nm(ubi_num, name, UBI_READONLY);
> +       else
> +               return ubi_open_volume(ubi_num, vol_id, UBI_READONLY);
> +}
> +
> +static void __init ubiblock_add_from_param(void)
> +{
> +       int i, ret;
> +       struct ubiblock_param *p;
> +       struct ubi_volume_desc *desc;
> +       struct ubi_volume_info vi;
> +
> +       for (i = 0; i < ubiblock_devs; i++) {
> +               p = &ubiblock_param[i];
> +
> +               desc = open_volume_desc(p->name, p->ubi_num, p->vol_id);
> +               if (IS_ERR(desc)) {
> +                       ubi_warn("block: can't open volume, err=%ld\n",
> +                                PTR_ERR(desc));
> +                       continue;
> +               }
> +
> +               ubi_get_volume_info(desc, &vi);
> +               ret = ubiblock_add(&vi);
> +               if (ret)
> +                       ubi_warn("block: can't add '%s' volume, err=%d\n",
> +                                vi.name, ret);
> +               ubi_close_volume(desc);
> +       }
> +}
> +
> +int __init ubiblock_init(void)
> +{
> +       int ret;
> +
> +       ubiblock_major = register_blkdev(0, "ubiblock");
> +       if (ubiblock_major < 0)
> +               return ubiblock_major;
> +
> +       /* Attach block devices from 'block=' module param */
> +       ubiblock_add_from_param();
> +
> +       /*
> +        * Block devices needs to be attached to volumes explicitly
> +        * upon user request. So we ignore existing volumes.
> +        */
> +       ret = ubi_register_volume_notifier(&ubiblock_notifier, 1);
> +       if (ret < 0)
> +               unregister_blkdev(ubiblock_major, "ubiblock");
> +       return ret;
> +}
> +
> +void __exit ubiblock_exit(void)
> +{
> +       struct ubiblock *next;
> +       struct ubiblock *dev;
> +
> +       ubi_unregister_volume_notifier(&ubiblock_notifier);
> +
> +       list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
> +
> +               /* Flush pending work and stop workqueue */
> +               destroy_workqueue(dev->wq);
> +
> +               /* The module is being forcefully removed */
> +               WARN_ON(dev->desc);
> +
> +               /* Remove from device list */
> +               list_del(&dev->list);
> +
> +               ubiblock_cleanup(dev);
> +
> +               kfree(dev);
> +       }
> +
> +       unregister_blkdev(ubiblock_major, "ubiblock");
> +}
> diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
> index e05dc62..2705bad 100644
> --- a/drivers/mtd/ubi/build.c
> +++ b/drivers/mtd/ubi/build.c
> @@ -1296,6 +1296,9 @@ static int __init ubi_init(void)
>                 }
>         }
>
> +       if (ubiblock_init() < 0)
> +               ubi_warn("cannot init block device access");
> +
>         return 0;
>
>  out_detach:
> @@ -1324,6 +1327,8 @@ static void __exit ubi_exit(void)
>  {
>         int i;
>
> +       ubiblock_exit();
> +
>         for (i = 0; i < UBI_MAX_DEVICES; i++)
>                 if (ubi_devices[i]) {
>                         mutex_lock(&ubi_devices_mutex);
> diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
> index 8ca49f2..39d3774 100644
> --- a/drivers/mtd/ubi/cdev.c
> +++ b/drivers/mtd/ubi/cdev.c
> @@ -561,6 +561,26 @@ static long vol_cdev_ioctl(struct file *file, unsigned int cmd,
>                 break;
>         }
>
> +       /* Attach a block device to an UBI volume */
> +       case UBI_IOCVOLATTBLK:
> +       {
> +               struct ubi_volume_info vi;
> +
> +               ubi_get_volume_info(desc, &vi);
> +               err = ubiblock_add(&vi);
> +               break;
> +       }
> +
> +       /* Dettach a block device from an UBI volume */
> +       case UBI_IOCVOLDETBLK:
> +       {
> +               struct ubi_volume_info vi;
> +
> +               ubi_get_volume_info(desc, &vi);
> +               err = ubiblock_del(&vi);
> +               break;
> +       }
> +
>         default:
>                 err = -ENOTTY;
>                 break;
> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
> index 8ea6297..e76ff98 100644
> --- a/drivers/mtd/ubi/ubi.h
> +++ b/drivers/mtd/ubi/ubi.h
> @@ -864,6 +864,20 @@ int ubi_update_fastmap(struct ubi_device *ubi);
>  int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
>                      int fm_anchor);
>
> +/* block.c */
> +#ifdef CONFIG_MTD_UBI_BLOCK
> +int ubiblock_init(void);
> +void ubiblock_exit(void);
> +int ubiblock_add(struct ubi_volume_info *vi);
> +int ubiblock_del(struct ubi_volume_info *vi);
> +#else
> +static inline int ubiblock_init(void) { return 0; }
> +static inline void ubiblock_exit(void) {}
> +static inline int ubiblock_add(struct ubi_volume_info *vi) { return -ENOTTY; }
> +static inline int ubiblock_del(struct ubi_volume_info *vi) { return -ENOTTY; }
> +#endif
> +
> +
>  /*
>   * ubi_rb_for_each_entry - walk an RB-tree.
>   * @rb: a pointer to type 'struct rb_node' to use as a loop counter
> diff --git a/include/uapi/mtd/ubi-user.h b/include/uapi/mtd/ubi-user.h
> index 723c324..1080762 100644
> --- a/include/uapi/mtd/ubi-user.h
> +++ b/include/uapi/mtd/ubi-user.h
> @@ -134,6 +134,13 @@
>   * used. A pointer to a &struct ubi_set_vol_prop_req object is expected to be
>   * passed. The object describes which property should be set, and to which value
>   * it should be set.
> + *
> + * Block device access to UBI volumes
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * To attach or detach a block device from an UBI volume the %UBI_IOCVOLATTBLK
> + * and %UBI_IOCVOLDETBLK ioctl commands should be used, respectively.
> + * These commands take no arguments.
>   */
>
>  /*
> @@ -191,6 +198,10 @@
>  /* Set an UBI volume property */
>  #define UBI_IOCSETVOLPROP _IOW(UBI_VOL_IOC_MAGIC, 6, \
>                                struct ubi_set_vol_prop_req)
> +/* Attach a block device to an UBI volume */
> +#define UBI_IOCVOLATTBLK _IO(UBI_VOL_IOC_MAGIC, 7)
> +/* Detach a block device from an UBI volume */
> +#define UBI_IOCVOLDETBLK _IO(UBI_VOL_IOC_MAGIC, 8)
>
>  /* Maximum MTD device name length supported by UBI */
>  #define MAX_UBI_MTD_NAME_LEN 127
> --
> 1.8.1.5
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/



-- 
Thanks,
//richard



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