ubi: fastmap: Add fastmap control support for 'UBI_IOCATT' ioctl

[1] suggests that fastmap is suitable for large flash devices. Module
parameter 'fm_autoconvert' is a coarse grained switch to enable all
ubi devices to generate fastmap, which may turn on fastmap even for
small flash devices.

This patch imports a new field 'disable_fm' in struct 'ubi_attach_req'
to support following situations by ioctl 'UBI_IOCATT'.
 [old functions]
 A. Disable 'fm_autoconvert': Disbable fastmap for all ubi devices
 B. Enable 'fm_autoconvert': Enable fastmap for all ubi devices
 [new function]
 C. Enable 'fm_autoconvert', set 'disable_fm' for given device: Don't
    create new fastmap and do full scan (existed fastmap will be
    destroyed) for the given ubi device.

A simple test case in [2].

[1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_fastmap
[2] https://bugzilla.kernel.org/show_bug.cgi?id=216278

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Author: Zhihao Cheng

drivers/mtd/ubi/build.c

@@ -807,18 +807,23 @@ static int autoresize(struct ubi_device *ubi, int vol_id)
  * @ubi_num: number to assign to the new UBI device
  * @vid_hdr_offset: VID header offset
  * @max_beb_per1024: maximum expected number of bad PEB per 1024 PEBs
+ * @disable_fm: whether disable fastmap
  *
  * This function attaches MTD device @mtd_dev to UBI and assign @ubi_num number
  * to the newly created UBI device, unless @ubi_num is %UBI_DEV_NUM_AUTO, in
  * which case this function finds a vacant device number and assigns it
  * automatically. Returns the new UBI device number in case of success and a
  * negative error code in case of failure.
  *
+ * If @disable_fm is true, ubi doesn't create new fastmap even the module param
+ * 'fm_autoconvert' is set, and existed old fastmap will be destroyed after
+ * doing full scanning.
+ *
  * Note, the invocations of this function has to be serialized by the
  * @ubi_devices_mutex.
  */
 int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
-		       int vid_hdr_offset, int max_beb_per1024)
+		       int vid_hdr_offset, int max_beb_per1024, bool disable_fm)
 {
 	struct ubi_device *ubi;
 	int i, err;
@@ -921,7 +926,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 		UBI_FM_MIN_POOL_SIZE);
 
 	ubi->fm_wl_pool.max_size = ubi->fm_pool.max_size / 2;
-	ubi->fm_disabled = !fm_autoconvert;
+	ubi->fm_disabled = (!fm_autoconvert || disable_fm) ? 1 : 0;
 	if (fm_debug)
 		ubi_enable_dbg_chk_fastmap(ubi);
 
@@ -962,7 +967,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 	if (!ubi->fm_buf)
 		goto out_free;
 #endif
-	err = ubi_attach(ubi, 0);
+	err = ubi_attach(ubi, disable_fm ? 1 : 0);
 	if (err) {
 		ubi_err(ubi, "failed to attach mtd%d, error %d",
 			mtd->index, err);
@@ -1242,7 +1247,8 @@ static int __init ubi_init(void)
 
 		mutex_lock(&ubi_devices_mutex);
 		err = ubi_attach_mtd_dev(mtd, p->ubi_num,
-					 p->vid_hdr_offs, p->max_beb_per1024);
+					 p->vid_hdr_offs, p->max_beb_per1024,
+					 false);
 		mutex_unlock(&ubi_devices_mutex);
 		if (err < 0) {
 			pr_err("UBI error: cannot attach mtd%d\n",

drivers/mtd/ubi/cdev.c

@@ -1041,7 +1041,7 @@ static long ctrl_cdev_ioctl(struct file *file, unsigned int cmd,
 		 */
 		mutex_lock(&ubi_devices_mutex);
 		err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset,
-					 req.max_beb_per1024);
+					 req.max_beb_per1024, !!req.disable_fm);
 		mutex_unlock(&ubi_devices_mutex);
 		if (err < 0)
 			put_mtd_device(mtd);

drivers/mtd/ubi/ubi.h

@@ -937,7 +937,8 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 
 /* build.c */
 int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
-		       int vid_hdr_offset, int max_beb_per1024);
+		       int vid_hdr_offset, int max_beb_per1024,
+		       bool disable_fm);
 int ubi_detach_mtd_dev(int ubi_num, int anyway);
 struct ubi_device *ubi_get_device(int ubi_num);
 void ubi_put_device(struct ubi_device *ubi);

include/uapi/mtd/ubi-user.h

@@ -247,6 +247,7 @@ enum {
  * @vid_hdr_offset: VID header offset (use defaults if %0)
  * @max_beb_per1024: maximum expected number of bad PEB per 1024 PEBs
  * @padding: reserved for future, not used, has to be zeroed
+ * @disable_fm: whether disable fastmap
  *
  * This data structure is used to specify MTD device UBI has to attach and the
  * parameters it has to use. The number which should be assigned to the new UBI
@@ -281,13 +282,18 @@ enum {
  * eraseblocks for new bad eraseblocks, but attempts to use available
  * eraseblocks (if any). The accepted range is 0-768. If 0 is given, the
  * default kernel value of %CONFIG_MTD_UBI_BEB_LIMIT will be used.
+ *
+ * If @disable_fm is not zero, ubi doesn't create new fastmap even the module
+ * param 'fm_autoconvert' is set, and existed old fastmap will be destroyed
+ * after doing full scanning.
  */
 struct ubi_attach_req {
 	__s32 ubi_num;
 	__s32 mtd_num;
 	__s32 vid_hdr_offset;
 	__s16 max_beb_per1024;
-	__s8 padding[10];
+	__s8 disable_fm;
+	__s8 padding[9];
 };
 
 /*