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Subject[PATCH V2] UBI: power cut emulation for testing
Date
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>
---
V2: Remove broken check to prevent multiple triggering
---
drivers/mtd/ubi/debug.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++--
drivers/mtd/ubi/debug.h | 2 ++
drivers/mtd/ubi/io.c | 6 ++++
drivers/mtd/ubi/ubi.h | 25 ++++++++++++++
4 files changed, 120 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index 7335c9f..aa9deca 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);
@@ -281,6 +281,22 @@ 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;
@@ -309,7 +325,7 @@ 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);
@@ -323,6 +339,21 @@ 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')
@@ -427,6 +458,27 @@ 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:
@@ -447,3 +499,36 @@ 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 cba89fc..d74b339 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -127,4 +127,6 @@ static inline int ubi_dbg_chk_gen(const struct ubi_device *ubi)
{
return ubi->dbg.chk_gen;
}
+
+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 ed0bcb3..5bbd1f0 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 c5be82d..4e0981a 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
@@ -359,6 +370,10 @@ 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
@@ -366,6 +381,9 @@ 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;
@@ -373,6 +391,10 @@ 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;
@@ -380,6 +402,9 @@ 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;
};

/**
--
2.3.4


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