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>

4 files changed, 120 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;
+}
diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
index c6ea4431acf3..eb8985e5c178 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -137,4 +137,6 @@ static inline void ubi_enable_dbg_chk_fastmap(struct ubi_device *ubi)
 {
         ubi->dbg.chk_fastmap = 1;
 }
+
+int ubi_dbg_power_cut(struct ubi_device *ubi, int caller);
 #endif /* !__UBI_DEBUG_H__ */
diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index ed0bcb35472f..5bbd1f094f4e 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -859,6 +859,9 @@ int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
         if (err)
                 return err;
 
+        if (ubi_dbg_power_cut(ubi, POWER_CUT_EC_WRITE))
+                return -EROFS;
+
         err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
         return err;
 }
@@ -1106,6 +1109,9 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
         if (err)
                 return err;
 
+        if (ubi_dbg_power_cut(ubi, POWER_CUT_VID_WRITE))
+                return -EROFS;
+
         p = (char *)vid_hdr - ubi->vid_hdr_shift;
         err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
                            ubi->vid_hdr_alsize);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 3d58c749f9f1..c998212fc680 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -151,6 +151,17 @@ enum {
         UBI_BAD_FASTMAP,
 };
 
+/*
+ * Flags for emulate_power_cut in ubi_debug_info
+ *
+ * POWER_CUT_EC_WRITE: Emulate a power cut when writing an EC header
+ * POWER_CUT_VID_WRITE: Emulate a power cut when writing a VID header
+ */
+enum {
+        POWER_CUT_EC_WRITE = 0x01,
+        POWER_CUT_VID_WRITE = 0x02,
+};
+
 /**
  * struct ubi_wl_entry - wear-leveling entry.
  * @u.rb: link in the corresponding (free/used) RB-tree
@@ -360,6 +371,10 @@ struct ubi_wl_entry;
  * @disable_bgt: disable the background task for testing purposes
  * @emulate_bitflips: emulate bit-flips for testing purposes
  * @emulate_io_failures: emulate write/erase failures for testing purposes
+ * @emulate_power_cut: emulate power cut for testing purposes
+ * @power_cut_counter: count down for writes left until emulated power cut
+ * @power_cut_min: minimum number of writes before emulating a power cut
+ * @power_cut_max: maximum number of writes until emulating a power cut
  * @dfs_dir_name: name of debugfs directory containing files of this UBI device
  * @dfs_dir: direntry object of the UBI device debugfs directory
  * @dfs_chk_gen: debugfs knob to enable UBI general extra checks
@@ -368,6 +383,9 @@ struct ubi_wl_entry;
  * @dfs_disable_bgt: debugfs knob to disable the background task
  * @dfs_emulate_bitflips: debugfs knob to emulate bit-flips
  * @dfs_emulate_io_failures: debugfs knob to emulate write/erase failures
+ * @dfs_emulate_power_cut: debugfs knob to emulate power cuts
+ * @dfs_power_cut_min: debugfs knob for minimum writes before power cut
+ * @dfs_power_cut_max: debugfs knob for maximum writes until power cut
  */
 struct ubi_debug_info {
         unsigned int chk_gen:1;
@@ -376,6 +394,10 @@ struct ubi_debug_info {
         unsigned int disable_bgt:1;
         unsigned int emulate_bitflips:1;
         unsigned int emulate_io_failures:1;
+        unsigned int emulate_power_cut:2;
+        unsigned int power_cut_counter;
+        unsigned int power_cut_min;
+        unsigned int power_cut_max;
         char dfs_dir_name[UBI_DFS_DIR_LEN + 1];
         struct dentry *dfs_dir;
         struct dentry *dfs_chk_gen;
@@ -384,6 +406,9 @@ struct ubi_debug_info {
         struct dentry *dfs_disable_bgt;
         struct dentry *dfs_emulate_bitflips;
         struct dentry *dfs_emulate_io_failures;
+        struct dentry *dfs_emulate_power_cut;
+        struct dentry *dfs_power_cut_min;
+        struct dentry *dfs_power_cut_max;
 };
 
 /**