dm flakey: add corrupt_bio_byte feature

Add corrupt_bio_byte feature to simulate corruption by overwriting a byte at a
specified position with a specified value during intervals when the device is
"down".

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
index 1b66c86..6ff5c23 100644 (file)
--- a/Documentation/device-mapper/dm-flakey.txt
+++ b/Documentation/device-mapper/dm-flakey.txt
@@ -32,3 +32,22 @@ Optional feature parameters:
   drop_writes:
        All write I/O is silently ignored.
        Read I/O is handled correctly.
+
+  corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
+       During <down interval>, replace <Nth_byte> of the data of
+       each matching bio with <value>.
+
+    <Nth_byte>: The offset of the byte to replace.
+               Counting starts at 1, to replace the first byte.
+    <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes.
+                'w' is incompatible with drop_writes.
+    <value>: The value (from 0-255) to write.
+    <flags>: Perform the replacement only if bio->bi_rw has all the
+            selected flags set.
+
+Examples:
+  corrupt_bio_byte 32 r 1 0
+       - replaces the 32nd byte of READ bios with the value 1
+
+  corrupt_bio_byte 224 w 0 32
+       - replaces the 224th byte of REQ_META (=32) bios with the value 0

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index e7c4c2a..89f73ca 100644 (file)
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2003 Sistina Software (UK) Limited.
- * Copyright (C) 2004, 2010 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
  *
  * This file is released under the GPL.
  */
@@ -15,6 +15,9 @@
 
 #define DM_MSG_PREFIX "flakey"
 
+#define all_corrupt_bio_flags_match(bio, fc)   \
+       (((bio)->bi_rw & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
+
 /*
  * Flakey: Used for testing only, simulates intermittent,
  * catastrophic device failure.
@@ -26,6 +29,10 @@ struct flakey_c {
        unsigned up_interval;
        unsigned down_interval;
        unsigned long flags;
+       unsigned corrupt_bio_byte;
+       unsigned corrupt_bio_rw;
+       unsigned corrupt_bio_value;
+       unsigned corrupt_bio_flags;
 };
 
 enum feature_flag_bits {
@@ -40,7 +47,10 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
        const char *arg_name;
 
        static struct dm_arg _args[] = {
-               {0, 1, "Invalid number of feature args"},
+               {0, 6, "Invalid number of feature args"},
+               {1, UINT_MAX, "Invalid corrupt bio byte"},
+               {0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
+               {0, UINT_MAX, "Invalid corrupt bio flags mask"},
        };
 
        /* No feature arguments supplied. */
@@ -49,9 +59,9 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
 
        r = dm_read_arg_group(_args, as, &argc, &ti->error);
        if (r)
-               return -EINVAL;
+               return r;
 
-       while (argc && !r) {
+       while (argc) {
                arg_name = dm_shift_arg(as);
                argc--;
 
@@ -67,11 +77,61 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
                        continue;
                }
 
+               /*
+                * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
+                */
+               if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
+                       if (!argc)
+                               ti->error = "Feature corrupt_bio_byte requires parameters";
+
+                       r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
+                       if (r)
+                               return r;
+                       argc--;
+
+                       /*
+                        * Direction r or w?
+                        */
+                       arg_name = dm_shift_arg(as);
+                       if (!strcasecmp(arg_name, "w"))
+                               fc->corrupt_bio_rw = WRITE;
+                       else if (!strcasecmp(arg_name, "r"))
+                               fc->corrupt_bio_rw = READ;
+                       else {
+                               ti->error = "Invalid corrupt bio direction (r or w)";
+                               return -EINVAL;
+                       }
+                       argc--;
+
+                       /*
+                        * Value of byte (0-255) to write in place of correct one.
+                        */
+                       r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
+                       if (r)
+                               return r;
+                       argc--;
+
+                       /*
+                        * Only corrupt bios with these flags set.
+                        */
+                       r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
+                       if (r)
+                               return r;
+                       argc--;
+
+                       continue;
+               }
+
                ti->error = "Unrecognised flakey feature requested";
-               r = -EINVAL;
+               return -EINVAL;
        }
 
-       return r;
+       if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
+               ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
+               return -EINVAL;
+       }
+
+       return 0;
 }
 
 /*
@@ -80,6 +140,11 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
  *
  *   Feature args:
  *     [drop_writes]
+ *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
+ *
+ *   Nth_byte starts from 1 for the first byte.
+ *   Direction is r for READ or w for WRITE.
+ *   bio_flags is ignored if 0.
  */
 static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
@@ -178,31 +243,64 @@ static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
                bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
 }
 
+static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
+{
+       unsigned bio_bytes = bio_cur_bytes(bio);
+       char *data = bio_data(bio);
+
+       /*
+        * Overwrite the Nth byte of the data returned.
+        */
+       if (data && bio_bytes >= fc->corrupt_bio_byte) {
+               data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
+
+               DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
+                       "(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
+                       bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
+                       (bio_data_dir(bio) == WRITE) ? 'w' : 'r',
+                       bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
+       }
+}
+
 static int flakey_map(struct dm_target *ti, struct bio *bio,
                      union map_info *map_context)
 {
        struct flakey_c *fc = ti->private;
        unsigned elapsed;
-       unsigned rw;
 
        /* Are we alive ? */
        elapsed = (jiffies - fc->start_time) / HZ;
        if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
-               rw = bio_data_dir(bio);
+               /*
+                * Flag this bio as submitted while down.
+                */
+               map_context->ll = 1;
+
+               /*
+                * Map reads as normal.
+                */
+               if (bio_data_dir(bio) == READ)
+                       goto map_bio;
 
                /*
-                * Drop writes.  Map reads as normal.
+                * Drop writes?
                 */
                if (test_bit(DROP_WRITES, &fc->flags)) {
-                       if (rw == WRITE) {
-                               bio_endio(bio, 0);
-                               return DM_MAPIO_SUBMITTED;
-                       }
+                       bio_endio(bio, 0);
+                       return DM_MAPIO_SUBMITTED;
+               }
+
+               /*
+                * Corrupt matching writes.
+                */
+               if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
+                       if (all_corrupt_bio_flags_match(bio, fc))
+                               corrupt_bio_data(bio, fc);
                        goto map_bio;
                }
 
                /*
-                * Default setting errors all I/O.
+                * By default, error all I/O.
                 */
                return -EIO;
        }
@@ -213,6 +311,24 @@ map_bio:
        return DM_MAPIO_REMAPPED;
 }
 
+static int flakey_end_io(struct dm_target *ti, struct bio *bio,
+                        int error, union map_info *map_context)
+{
+       struct flakey_c *fc = ti->private;
+       unsigned bio_submitted_while_down = map_context->ll;
+
+       /*
+        * Corrupt successful READs while in down state.
+        * If flags were specified, only corrupt those that match.
+        */
+       if (!error && bio_submitted_while_down &&
+           (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
+           all_corrupt_bio_flags_match(bio, fc))
+               corrupt_bio_data(bio, fc);
+
+       return error;
+}
+
 static int flakey_status(struct dm_target *ti, status_type_t type,
                         char *result, unsigned int maxlen)
 {
@@ -231,9 +347,17 @@ static int flakey_status(struct dm_target *ti, status_type_t type,
                       fc->down_interval);
 
                drop_writes = test_bit(DROP_WRITES, &fc->flags);
-               DMEMIT("%u ", drop_writes);
+               DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
+
                if (drop_writes)
                        DMEMIT("drop_writes ");
+
+               if (fc->corrupt_bio_byte)
+                       DMEMIT("corrupt_bio_byte %u %c %u %u ",
+                              fc->corrupt_bio_byte,
+                              (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
+                              fc->corrupt_bio_value, fc->corrupt_bio_flags);
+
                break;
        }
        return 0;
@@ -275,6 +399,7 @@ static struct target_type flakey_target = {
        .ctr    = flakey_ctr,
        .dtr    = flakey_dtr,
        .map    = flakey_map,
+       .end_io = flakey_end_io,
        .status = flakey_status,
        .ioctl  = flakey_ioctl,
        .merge  = flakey_merge,