UBI: power cut emulation for testing

Emulate random power cuts by switching device to ro after a number of
writes to allow simple power cut testing with nand-sim.

Maximum and minimum number of successful writes before power cut and
what kind of writes (EC header, VID header or none) to interrupt
configurable via debugfs.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 87 insertions, 2 deletions

diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index 224fed085102..b077e43b5ba9 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -263,7 +263,7 @@ static ssize_t dfs_file_read(struct file *file, char __user *user_buf,
         struct dentry *dent = file->f_path.dentry;
         struct ubi_device *ubi;
         struct ubi_debug_info *d;
-        char buf[3];
+        char buf[8];
         int val;
 
         ubi = ubi_get_device(ubi_num);
@@ -283,6 +283,22 @@ static ssize_t dfs_file_read(struct file *file, char __user *user_buf,
                 val = d->emulate_bitflips;
         else if (dent == d->dfs_emulate_io_failures)
                 val = d->emulate_io_failures;
+        else if (dent == d->dfs_emulate_power_cut) {
+                snprintf(buf, sizeof(buf), "%u\n", d->emulate_power_cut);
+                count = simple_read_from_buffer(user_buf, count, ppos,
+                                                buf, strlen(buf));
+                goto out;
+        } else if (dent == d->dfs_power_cut_min) {
+                snprintf(buf, sizeof(buf), "%u\n", d->power_cut_min);
+                count = simple_read_from_buffer(user_buf, count, ppos,
+                                                buf, strlen(buf));
+                goto out;
+        } else if (dent == d->dfs_power_cut_max) {
+                snprintf(buf, sizeof(buf), "%u\n", d->power_cut_max);
+                count = simple_read_from_buffer(user_buf, count, ppos,
+                                                buf, strlen(buf));
+                goto out;
+        }
         else {
                 count = -EINVAL;
                 goto out;
@@ -311,7 +327,7 @@ static ssize_t dfs_file_write(struct file *file, const char __user *user_buf,
         struct ubi_device *ubi;
         struct ubi_debug_info *d;
         size_t buf_size;
-        char buf[8];
+        char buf[8] = {0};
         int val;
 
         ubi = ubi_get_device(ubi_num);
@@ -325,6 +341,21 @@ static ssize_t dfs_file_write(struct file *file, const char __user *user_buf,
                 goto out;
         }
 
+        if (dent == d->dfs_power_cut_min) {
+                if (kstrtouint(buf, 0, &d->power_cut_min) != 0)
+                        count = -EINVAL;
+                goto out;
+        } else if (dent == d->dfs_power_cut_max) {
+                if (kstrtouint(buf, 0, &d->power_cut_max) != 0)
+                        count = -EINVAL;
+                goto out;
+        } else if (dent == d->dfs_emulate_power_cut) {
+                if (kstrtoint(buf, 0, &val) != 0)
+                        count = -EINVAL;
+                d->emulate_power_cut = val;
+                goto out;
+        }
+
         if (buf[0] == '1')
                 val = 1;
         else if (buf[0] == '0')
@@ -438,6 +469,27 @@ int ubi_debugfs_init_dev(struct ubi_device *ubi)
                 goto out_remove;
         d->dfs_emulate_io_failures = dent;
 
+        fname = "tst_emulate_power_cut";
+        dent = debugfs_create_file(fname, S_IWUSR, d->dfs_dir, (void *)ubi_num,
+                                   &dfs_fops);
+        if (IS_ERR_OR_NULL(dent))
+                goto out_remove;
+        d->dfs_emulate_power_cut = dent;
+
+        fname = "tst_emulate_power_cut_min";
+        dent = debugfs_create_file(fname, S_IWUSR, d->dfs_dir, (void *)ubi_num,
+                                   &dfs_fops);
+        if (IS_ERR_OR_NULL(dent))
+                goto out_remove;
+        d->dfs_power_cut_min = dent;
+
+        fname = "tst_emulate_power_cut_max";
+        dent = debugfs_create_file(fname, S_IWUSR, d->dfs_dir, (void *)ubi_num,
+                                   &dfs_fops);
+        if (IS_ERR_OR_NULL(dent))
+                goto out_remove;
+        d->dfs_power_cut_max = dent;
+
         return 0;
 
 out_remove:
@@ -458,3 +510,36 @@ void ubi_debugfs_exit_dev(struct ubi_device *ubi)
         if (IS_ENABLED(CONFIG_DEBUG_FS))
                 debugfs_remove_recursive(ubi->dbg.dfs_dir);
 }
+
+/**
+ * ubi_dbg_power_cut - emulate a power cut if it is time to do so
+ * @ubi: UBI device description object
+ * @caller: Flags set to indicate from where the function is being called
+ *
+ * Returns non-zero if a power cut was emulated, zero if not.
+ */
+int ubi_dbg_power_cut(struct ubi_device *ubi, int caller)
+{
+        unsigned int range;
+
+        if ((ubi->dbg.emulate_power_cut & caller) == 0)
+                return 0;
+
+        if (ubi->dbg.power_cut_counter == 0) {
+                ubi->dbg.power_cut_counter = ubi->dbg.power_cut_min;
+
+                if (ubi->dbg.power_cut_max > ubi->dbg.power_cut_min) {
+                        range = ubi->dbg.power_cut_max - ubi->dbg.power_cut_min;
+                        ubi->dbg.power_cut_counter += prandom_u32() % range;
+                }
+                return 0;
+        }
+
+        ubi->dbg.power_cut_counter--;
+        if (ubi->dbg.power_cut_counter)
+                return 0;
+
+        ubi_msg(ubi, "XXXXXXXXXXXXXXX emulating a power cut XXXXXXXXXXXXXXXX");
+        ubi_ro_mode(ubi);
+        return 1;
+}