brassow
This patch gives mirror the ability to handle write failures
during recovery.
We check over the bits in 'write_err' and call a new function,
fail_mirror, on those devices whose bit is set. 'fail_mirror'
increments the error_count on the mirror device, and will
switch the primary device pointer for the mirror set if the
mirror is in-sync.
To maintain backwards compatibility, fail_mirror does nothing
if the DM_FEATURES_HANDLE_ERRORS flag is not present.
Index: linux-2.6.22-rc1-mm1/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.22-rc1-mm1.orig/drivers/md/dm-raid1.c
+++ linux-2.6.22-rc1-mm1/drivers/md/dm-raid1.c
@@ -113,6 +113,7 @@ struct region {
*---------------------------------------------------------------*/
struct mirror {
atomic_t error_count;
+ struct mirror_set *ms;
struct dm_dev *dev;
sector_t offset;
};
@@ -653,19 +654,37 @@ static void bio_set_ms(struct bio *bio,
* are in the no-sync state. We have to recover these by
* recopying from the default mirror to all the others.
*---------------------------------------------------------------*/
+static void fail_mirror(struct mirror *m);
static void recovery_complete(int read_err, unsigned int write_err,
void *context)
{
struct region *reg = (struct region *) context;
+ struct mirror_set *ms = reg->rh->ms;
+ int m, bit = 0;
if (read_err)
/* Read error means the failure of default mirror. */
DMERR_LIMIT("Unable to read primary mirror during recovery");
- if (write_err)
+ if (write_err) {
DMERR_LIMIT("Write error during recovery (error = 0x%x)",
write_err);
+ /*
+ * Bits correspond to devices (excluding default mirror).
+ * The default mirror cannot change during recovery.
+ */
+ for (m = 0; m < ms->nr_mirrors; m++) {
+ if (&ms->mirror[m] == ms->default_mirror)
+ continue;
+
+ /* FIXME: does write_err need to be 'unsigned long'? */
+ if (test_bit(bit, &write_err))
+ fail_mirror(ms->mirror + m);
+ bit++;
+ }
+ }
+
rh_recovery_end(reg, !(read_err || write_err));
}
@@ -752,6 +771,55 @@ static struct mirror *choose_mirror(stru
return ms->default_mirror;
}
+/* fail_mirror
+ * @m: mirror device to fail
+ *
+ * If the device is valid, mark it invalid. Also,
+ * if this is the default mirror device (i.e. the primary
+ * device) and the mirror set is in-sync, choose an
+ * alternate primary device.
+ *
+ * This function must not block
+ */
+static void fail_mirror(struct mirror *m)
+{
+ struct mirror_set *ms = m->ms;
+ struct mirror *new;
+
+ /* Are we handling or ignoring device failures */
+ if (!(ms->features & DM_RAID1_HANDLE_ERRORS))
+ return;
+
+ atomic_inc(&m->error_count);
+
+ if (atomic_read(&m->error_count) > 1)
+ return;
+
+ if (m != ms->default_mirror)
+ return;
+
+ /* If the default mirror fails, change it. */
+ if (!ms->in_sync) {
+ /*
+ * Can not switch primary. Better to issue requests
+ * to same failing device than to risk returning
+ * corrupt data.
+ */
+ DMERR("Primary mirror device has failed while mirror is not in-sync");
+ DMERR("Unable to choose alternative primary device");
+ return;
+ }
+
+ for (new = ms->mirror; new < ms->mirror + ms->nr_mirrors; new++)
+ if (!atomic_read(&new->error_count)) {
+ ms->default_mirror = new;
+ break;
+ }
+
+ if (unlikely(new == ms->mirror + ms->nr_mirrors))
+ DMWARN("All sides of mirror have failed.");
+}
+
/*
* remap a buffer to a particular mirror.
*/
@@ -1020,6 +1088,8 @@ static int get_mirror(struct mirror_set
}
ms->mirror[mirror].offset = offset;
+ atomic_set(&(ms->mirror[mirror].error_count), 0);
+ ms->mirror[mirror].ms = ms;
return 0;
}
--
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