UBI: make gluebi a separate module

[Artem: re-worked the patch: made it release resources when the
module is unloaded, made it do module referencing, made it really
independent on UBI, tested it with the UBI test-suite which can
be found in ubi-2.6.git/tests/ubi-tests, re-named most of the
funcs/variables to get rid of the "ubi" word and make names
consistent.]

Signed-off-by: Dmitry Pervushin <dpervushin@embeddedalley.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

3 files changed, 295 insertions, 98 deletions

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 3f063108e95f..b1cd7a1a2191 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -49,15 +49,16 @@ config MTD_UBI_BEB_RESERVE
           reserved. Leave the default value if unsure.
 
 config MTD_UBI_GLUEBI
-        bool "Emulate MTD devices"
+        tristate "MTD devices emulation driver (gluebi)"
         default n
         depends on MTD_UBI
         help
-           This option enables MTD devices emulation on top of UBI volumes: for
-           each UBI volumes an MTD device is created, and all I/O to this MTD
-           device is redirected to the UBI volume. This is handy to make
-           MTD-oriented software (like JFFS2) work on top of UBI. Do not enable
-           this if no legacy software will be used.
+           This option enables gluebi - an additional driver which emulates MTD
+           devices on top of UBI volumes: for each UBI volumes an MTD device is
+           created, and all I/O to this MTD device is redirected to the UBI
+           volume. This is handy to make MTD-oriented software (like JFFS2)
+           work on top of UBI. Do not enable this unless you use legacy
+           software.
 
 source "drivers/mtd/ubi/Kconfig.debug"
 endmenu
diff --git a/drivers/mtd/ubi/Makefile b/drivers/mtd/ubi/Makefile
index dd834e04151b..c9302a5452b0 100644
--- a/drivers/mtd/ubi/Makefile
+++ b/drivers/mtd/ubi/Makefile
@@ -4,4 +4,4 @@ ubi-y += vtbl.o vmt.o upd.o build.o cdev.o kapi.o eba.o io.o wl.o scan.o
 ubi-y += misc.o
 
 ubi-$(CONFIG_MTD_UBI_DEBUG) += debug.o
-ubi-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
+obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
diff --git a/drivers/mtd/ubi/gluebi.c b/drivers/mtd/ubi/gluebi.c
index 49cd55ade9c8..95aaac03f938 100644
--- a/drivers/mtd/ubi/gluebi.c
+++ b/drivers/mtd/ubi/gluebi.c
@@ -19,17 +19,71 @@
  */
 
 /*
- * This file includes implementation of fake MTD devices for each UBI volume.
- * This sounds strange, but it is in fact quite useful to make MTD-oriented
- * software (including all the legacy software) to work on top of UBI.
+ * This is a small driver which implements fake MTD devices on top of UBI
+ * volumes. This sounds strange, but it is in fact quite useful to make
+ * MTD-oriented software (including all the legacy software) work on top of
+ * UBI.
  *
  * Gluebi emulates MTD devices of "MTD_UBIVOLUME" type. Their minimal I/O unit
- * size (mtd->writesize) is equivalent to the UBI minimal I/O unit. The
+ * size (@mtd->writesize) is equivalent to the UBI minimal I/O unit. The
  * eraseblock size is equivalent to the logical eraseblock size of the volume.
  */
 
+#include <linux/err.h>
+#include <linux/list.h>
+#include <linux/sched.h>
 #include <linux/math64.h>
-#include "ubi.h"
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/mtd/ubi.h>
+#include <linux/mtd/mtd.h>
+#include "ubi-media.h"
+
+#define err_msg(fmt, ...)                                   \
+        printk(KERN_DEBUG "gluebi (pid %d): %s: " fmt "\n", \
+               current->pid, __func__, ##__VA_ARGS__)
+
+/**
+ * struct gluebi_device - a gluebi device description data structure.
+ * @mtd: emulated MTD device description object
+ * @refcnt: gluebi device reference count
+ * @desc: UBI volume descriptor
+ * @ubi_num: UBI device number this gluebi device works on
+ * @vol_id: ID of UBI volume this gluebi device works on
+ * @list: link in a list of gluebi devices
+ */
+struct gluebi_device {
+        struct mtd_info mtd;
+        int refcnt;
+        struct ubi_volume_desc *desc;
+        int ubi_num;
+        int vol_id;
+        struct list_head list;
+};
+
+/* List of all gluebi devices */
+static LIST_HEAD(gluebi_devices);
+static DEFINE_MUTEX(devices_mutex);
+
+/**
+ * find_gluebi_nolock - find a gluebi device.
+ * @ubi_num: UBI device number
+ * @vol_id: volume ID
+ *
+ * This function seraches for gluebi device corresponding to UBI device
+ * @ubi_num and UBI volume @vol_id. Returns the gluebi device description
+ * object in case of success and %NULL in case of failure. The caller has to
+ * have the &devices_mutex locked.
+ */
+static struct gluebi_device *find_gluebi_nolock(int ubi_num, int vol_id)
+{
+        struct gluebi_device *gluebi;
+
+        list_for_each_entry(gluebi, &gluebi_devices, list)
+                if (gluebi->ubi_num == ubi_num && gluebi->vol_id == vol_id)
+                        return gluebi;
+        return NULL;
+}
 
 /**
  * gluebi_get_device - get MTD device reference.
@@ -41,15 +95,18 @@
  */
 static int gluebi_get_device(struct mtd_info *mtd)
 {
-        struct ubi_volume *vol;
+        struct gluebi_device *gluebi;
+        int ubi_mode = UBI_READONLY;
 
-        vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
+        if (!try_module_get(THIS_MODULE))
+                return -ENODEV;
 
-        /*
-         * We do not introduce locks for gluebi reference count because the
-         * get_device()/put_device() calls are already serialized at MTD.
-         */
-        if (vol->gluebi_refcount > 0) {
+        if (mtd->flags & MTD_WRITEABLE)
+                ubi_mode = UBI_READWRITE;
+
+        gluebi = container_of(mtd, struct gluebi_device, mtd);
+        mutex_lock(&devices_mutex);
+        if (gluebi->refcnt > 0) {
                 /*
                  * The MTD device is already referenced and this is just one
                  * more reference. MTD allows many users to open the same
@@ -58,7 +115,8 @@ static int gluebi_get_device(struct mtd_info *mtd)
                  * open the UBI volume again - just increase the reference
                  * counter and return.
                  */
-                vol->gluebi_refcount += 1;
+                gluebi->refcnt += 1;
+                mutex_unlock(&devices_mutex);
                 return 0;
         }
 
@@ -66,11 +124,15 @@ static int gluebi_get_device(struct mtd_info *mtd)
          * This is the first reference to this UBI volume via the MTD device
          * interface. Open the corresponding volume in read-write mode.
          */
-        vol->gluebi_desc = ubi_open_volume(vol->ubi->ubi_num, vol->vol_id,
-                                           UBI_READWRITE);
-        if (IS_ERR(vol->gluebi_desc))
-                return PTR_ERR(vol->gluebi_desc);
-        vol->gluebi_refcount += 1;
+        gluebi->desc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id,
+                                       ubi_mode);
+        if (IS_ERR(gluebi->desc)) {
+                mutex_unlock(&devices_mutex);
+                module_put(THIS_MODULE);
+                return PTR_ERR(gluebi->desc);
+        }
+        gluebi->refcnt += 1;
+        mutex_unlock(&devices_mutex);
         return 0;
 }
 
@@ -83,13 +145,15 @@ static int gluebi_get_device(struct mtd_info *mtd)
  */
 static void gluebi_put_device(struct mtd_info *mtd)
 {
-        struct ubi_volume *vol;
-
-        vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
-        vol->gluebi_refcount -= 1;
-        ubi_assert(vol->gluebi_refcount >= 0);
-        if (vol->gluebi_refcount == 0)
-                ubi_close_volume(vol->gluebi_desc);
+        struct gluebi_device *gluebi;
+
+        gluebi = container_of(mtd, struct gluebi_device, mtd);
+        mutex_lock(&devices_mutex);
+        gluebi->refcnt -= 1;
+        if (gluebi->refcnt == 0)
+                ubi_close_volume(gluebi->desc);
+        module_put(THIS_MODULE);
+        mutex_unlock(&devices_mutex);
 }
 
 /**
@@ -107,16 +171,12 @@ static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
                        size_t *retlen, unsigned char *buf)
 {
         int err = 0, lnum, offs, total_read;
-        struct ubi_volume *vol;
-        struct ubi_device *ubi;
-
-        dbg_gen("read %zd bytes from offset %lld", len, from);
+        struct gluebi_device *gluebi;
 
         if (len < 0 || from < 0 || from + len > mtd->size)
                 return -EINVAL;
 
-        vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
-        ubi = vol->ubi;
+        gluebi = container_of(mtd, struct gluebi_device, mtd);
 
         lnum = div_u64_rem(from, mtd->erasesize, &offs);
         total_read = len;
@@ -126,7 +186,7 @@ static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
                 if (to_read > total_read)
                         to_read = total_read;
 
-                err = ubi_eba_read_leb(ubi, vol, lnum, buf, offs, to_read, 0);
+                err = ubi_read(gluebi->desc, lnum, buf, offs, to_read);
                 if (err)
                         break;
 
@@ -152,21 +212,17 @@ static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
  * case of failure.
  */
 static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
-                       size_t *retlen, const u_char *buf)
+                        size_t *retlen, const u_char *buf)
 {
         int err = 0, lnum, offs, total_written;
-        struct ubi_volume *vol;
-        struct ubi_device *ubi;
-
-        dbg_gen("write %zd bytes to offset %lld", len, to);
+        struct gluebi_device *gluebi;
 
         if (len < 0 || to < 0 || len + to > mtd->size)
                 return -EINVAL;
 
-        vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
-        ubi = vol->ubi;
+        gluebi = container_of(mtd, struct gluebi_device, mtd);
 
-        if (ubi->ro_mode)
+        if (!(mtd->flags & MTD_WRITEABLE))
                 return -EROFS;
 
         lnum = div_u64_rem(to, mtd->erasesize, &offs);
@@ -181,8 +237,7 @@ static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
                 if (to_write > total_written)
                         to_write = total_written;
 
-                err = ubi_eba_write_leb(ubi, vol, lnum, buf, offs, to_write,
-                                        UBI_UNKNOWN);
+                err = ubi_write(gluebi->desc, lnum, buf, offs, to_write);
                 if (err)
                         break;
 
@@ -207,41 +262,36 @@ static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
 static int gluebi_erase(struct mtd_info *mtd, struct erase_info *instr)
 {
         int err, i, lnum, count;
-        struct ubi_volume *vol;
-        struct ubi_device *ubi;
-
-        dbg_gen("erase %llu bytes at offset %llu", (unsigned long long)instr->len,
-                 (unsigned long long)instr->addr);
+        struct gluebi_device *gluebi;
 
         if (instr->addr < 0 || instr->addr > mtd->size - mtd->erasesize)
                 return -EINVAL;
-
         if (instr->len < 0 || instr->addr + instr->len > mtd->size)
                 return -EINVAL;
-
         if (mtd_mod_by_ws(instr->addr, mtd) || mtd_mod_by_ws(instr->len, mtd))
                 return -EINVAL;
 
         lnum = mtd_div_by_eb(instr->addr, mtd);
         count = mtd_div_by_eb(instr->len, mtd);
 
-        vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
-        ubi = vol->ubi;
+        gluebi = container_of(mtd, struct gluebi_device, mtd);
 
-        if (ubi->ro_mode)
+        if (!(mtd->flags & MTD_WRITEABLE))
                 return -EROFS;
 
-        for (i = 0; i < count; i++) {
-                err = ubi_eba_unmap_leb(ubi, vol, lnum + i);
+        for (i = 0; i < count - 1; i++) {
+                err = ubi_leb_unmap(gluebi->desc, lnum + i);
                 if (err)
                         goto out_err;
         }
-
         /*
          * MTD erase operations are synchronous, so we have to make sure the
          * physical eraseblock is wiped out.
+         *
+         * Thus, perform leb_erase instead of leb_unmap operation - leb_erase
+         * will wait for the end of operations
          */
-        err = ubi_wl_flush(ubi);
+        err = ubi_leb_erase(gluebi->desc, lnum + i);
         if (err)
                 goto out_err;
 
@@ -256,28 +306,38 @@ out_err:
 }
 
 /**
- * ubi_create_gluebi - initialize gluebi for an UBI volume.
- * @ubi: UBI device description object
- * @vol: volume description object
+ * gluebi_create - create a gluebi device for an UBI volume.
+ * @di: UBI device description object
+ * @vi: UBI volume description object
  *
- * This function is called when an UBI volume is created in order to create
+ * This function is called when a new UBI volume is created in order to create
  * corresponding fake MTD device. Returns zero in case of success and a
  * negative error code in case of failure.
  */
-int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol)
+static int gluebi_create(struct ubi_device_info *di,
+                         struct ubi_volume_info *vi)
 {
-        struct mtd_info *mtd = &vol->gluebi_mtd;
+        struct gluebi_device *gluebi, *g;
+        struct mtd_info *mtd;
 
-        mtd->name = kmemdup(vol->name, vol->name_len + 1, GFP_KERNEL);
-        if (!mtd->name)
+        gluebi = kzalloc(sizeof(struct gluebi_device), GFP_KERNEL);
+        if (!gluebi)
                 return -ENOMEM;
 
+        mtd = &gluebi->mtd;
+        mtd->name = kmemdup(vi->name, vi->name_len + 1, GFP_KERNEL);
+        if (!mtd->name) {
+                kfree(gluebi);
+                return -ENOMEM;
+        }
+
+        gluebi->vol_id = vi->vol_id;
         mtd->type = MTD_UBIVOLUME;
-        if (!ubi->ro_mode)
+        if (!di->ro_mode)
                 mtd->flags = MTD_WRITEABLE;
-        mtd->writesize  = ubi->min_io_size;
         mtd->owner      = THIS_MODULE;
-        mtd->erasesize  = vol->usable_leb_size;
+        mtd->writesize  = di->min_io_size;
+        mtd->erasesize  = vi->usable_leb_size;
         mtd->read       = gluebi_read;
         mtd->write      = gluebi_write;
         mtd->erase      = gluebi_erase;
@@ -285,60 +345,196 @@ int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol)
         mtd->put_device = gluebi_put_device;
 
         /*
-         * In case of dynamic volume, MTD device size is just volume size. In
+         * In case of dynamic a volume, MTD device size is just volume size. In
          * case of a static volume the size is equivalent to the amount of data
          * bytes.
          */
-        if (vol->vol_type == UBI_DYNAMIC_VOLUME)
-                mtd->size = (long long)vol->usable_leb_size * vol->reserved_pebs;
+        if (vi->vol_type == UBI_DYNAMIC_VOLUME)
+                mtd->size = (unsigned long long)vi->usable_leb_size * vi->size;
         else
-                mtd->size = vol->used_bytes;
+                mtd->size = vi->used_bytes;
+
+        /* Just a sanity check - make sure this gluebi device does not exist */
+        mutex_lock(&devices_mutex);
+        g = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
+        if (g)
+                err_msg("gluebi MTD device %d form UBI device %d volume %d "
+                        "already exists", g->mtd.index, vi->ubi_num,
+                        vi->vol_id);
+        mutex_unlock(&devices_mutex);
 
         if (add_mtd_device(mtd)) {
-                ubi_err("cannot not add MTD device");
+                err_msg("cannot add MTD device");
                 kfree(mtd->name);
+                kfree(gluebi);
                 return -ENFILE;
         }
 
-        dbg_gen("added mtd%d (\"%s\"), size %llu, EB size %u",
-                mtd->index, mtd->name, (unsigned long long)mtd->size, mtd->erasesize);
+        mutex_lock(&devices_mutex);
+        list_add_tail(&gluebi->list, &gluebi_devices);
+        mutex_unlock(&devices_mutex);
         return 0;
 }
 
 /**
- * ubi_destroy_gluebi - close gluebi for an UBI volume.
- * @vol: volume description object
+ * gluebi_remove - remove a gluebi device.
+ * @vi: UBI volume description object
  *
- * This function is called when an UBI volume is removed in order to remove
+ * This function is called when an UBI volume is removed and it removes
  * corresponding fake MTD device. Returns zero in case of success and a
  * negative error code in case of failure.
  */
-int ubi_destroy_gluebi(struct ubi_volume *vol)
+static int gluebi_remove(struct ubi_volume_info *vi)
 {
-        int err;
-        struct mtd_info *mtd = &vol->gluebi_mtd;
+        int err = 0;
+        struct mtd_info *mtd;
+        struct gluebi_device *gluebi;
+
+        mutex_lock(&devices_mutex);
+        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
+        if (!gluebi) {
+                err_msg("got remove notification for unknown UBI device %d "
+                        "volume %d", vi->ubi_num, vi->vol_id);
+                err = -ENOENT;
+        } else if (gluebi->refcnt)
+                err = -EBUSY;
+        else
+                list_del(&gluebi->list);
+        mutex_unlock(&devices_mutex);
+        if (err)
+                return err;
 
-        dbg_gen("remove mtd%d", mtd->index);
+        mtd = &gluebi->mtd;
         err = del_mtd_device(mtd);
-        if (err)
+        if (err) {
+                err_msg("cannot remove fake MTD device %d, UBI device %d, "
+                        "volume %d, error %d", mtd->index, gluebi->ubi_num,
+                        gluebi->vol_id, err);
+                mutex_lock(&devices_mutex);
+                list_add_tail(&gluebi->list, &gluebi_devices);
+                mutex_unlock(&devices_mutex);
                 return err;
+        }
+
         kfree(mtd->name);
+        kfree(gluebi);
         return 0;
 }
 
 /**
- * ubi_gluebi_updated - UBI volume was updated notifier.
- * @vol: volume description object
+ * gluebi_updated - UBI volume was updated notifier.
+ * @vi: volume info structure
  *
- * This function is called every time an UBI volume is updated. This function
- * does nothing if volume @vol is dynamic, and changes MTD device size if the
+ * This function is called every time an UBI volume is updated. It does nothing
+ * if te volume @vol is dynamic, and changes MTD device size if the
  * volume is static. This is needed because static volumes cannot be read past
- * data they contain.
+ * data they contain. This function returns zero in case of success and a
+ * negative error code in case of error.
+ */
+static int gluebi_updated(struct ubi_volume_info *vi)
+{
+        struct gluebi_device *gluebi;
+
+        mutex_lock(&devices_mutex);
+        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
+        if (!gluebi) {
+                mutex_unlock(&devices_mutex);
+                err_msg("got update notification for unknown UBI device %d "
+                        "volume %d", vi->ubi_num, vi->vol_id);
+                return -ENOENT;
+        }
+
+        if (vi->vol_type == UBI_STATIC_VOLUME)
+                gluebi->mtd.size = vi->used_bytes;
+        mutex_unlock(&devices_mutex);
+        return 0;
+}
+
+/**
+ * gluebi_resized - UBI volume was re-sized notifier.
+ * @vi: volume info structure
+ *
+ * This function is called every time an UBI volume is re-size. It changes the
+ * corresponding fake MTD device size. This function returns zero in case of
+ * success and a negative error code in case of error.
+ */
+static int gluebi_resized(struct ubi_volume_info *vi)
+{
+        struct gluebi_device *gluebi;
+
+        mutex_lock(&devices_mutex);
+        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
+        if (!gluebi) {
+                mutex_unlock(&devices_mutex);
+                err_msg("got update notification for unknown UBI device %d "
+                        "volume %d", vi->ubi_num, vi->vol_id);
+                return -ENOENT;
+        }
+        gluebi->mtd.size = vi->used_bytes;
+        mutex_unlock(&devices_mutex);
+        return 0;
+}
+
+/**
+ * gluebi_notify - UBI notification handler.
+ * @nb: registered notifier block
+ * @l: notification type
+ * @ptr: pointer to the &struct ubi_notification object
  */
-void ubi_gluebi_updated(struct ubi_volume *vol)
+static int gluebi_notify(struct notifier_block *nb, unsigned long l,
+                         void *ns_ptr)
 {
-        struct mtd_info *mtd = &vol->gluebi_mtd;
+        struct ubi_notification *nt = ns_ptr;
+
+        switch (l) {
+        case UBI_VOLUME_ADDED:
+                gluebi_create(&nt->di, &nt->vi);
+                break;
+        case UBI_VOLUME_REMOVED:
+                gluebi_remove(&nt->vi);
+                break;
+        case UBI_VOLUME_RESIZED:
+                gluebi_resized(&nt->vi);
+                break;
+        case UBI_VOLUME_UPDATED:
+                gluebi_updated(&nt->vi);
+                break;
+        default:
+                break;
+        }
+        return NOTIFY_OK;
+}
 
-        if (vol->vol_type == UBI_STATIC_VOLUME)
-                mtd->size = vol->used_bytes;
+static struct notifier_block gluebi_notifier = {
+        .notifier_call  = gluebi_notify,
+};
+
+static int __init ubi_gluebi_init(void)
+{
+        return ubi_register_volume_notifier(&gluebi_notifier, 0);
 }
+
+static void __exit ubi_gluebi_exit(void)
+{
+        struct gluebi_device *gluebi, *g;
+
+        list_for_each_entry_safe(gluebi, g, &gluebi_devices, list) {
+                int err;
+                struct mtd_info *mtd = &gluebi->mtd;
+
+                err = del_mtd_device(mtd);
+                if (err)
+                        err_msg("error %d while removing gluebi MTD device %d, "
+                                "UBI device %d, volume %d - ignoring", err,
+                                mtd->index, gluebi->ubi_num, gluebi->vol_id);
+                kfree(mtd->name);
+                kfree(gluebi);
+        }
+        ubi_unregister_volume_notifier(&gluebi_notifier);
+}
+
+module_init(ubi_gluebi_init);
+module_exit(ubi_gluebi_exit);
+MODULE_DESCRIPTION("MTD emulation layer over UBI volumes");
+MODULE_AUTHOR("Artem Bityutskiy, Joern Engel");
+MODULE_LICENSE("GPL");