TESTERS WANTED!! SEE BELOW...
This patch changes the behaviour of raid5 when it gets a read error.
Instead of just failing the device, it tried to find out what should
have been there, and writes it over the bad block. For some
media-errors, this has a reasonable chance of fixing the error.
If the write succeeds, and a subsequent read succeeds as well, raid5
decided the address is OK and conitnues.
I have tested this using the 'faulty' md personality, but it would be
really good to test it with real disks that have real errors. If
anyone has such drives in a cupboard (or even in a computer) and would
be willing to give this a try, I would really appreciate it.
Meanwhile, I think it is OK to go into -mm, but certainly not to go to
Linus yet.
Thanks,
NeilBrown
### Comments for Changeset
Instead of failing a drive on read-error, we attempt to
re-write the block, and then re-read. If that all works,
we allow the device to remain in the array.
Signed-off-by: Neil Brown <neilb@xxxxxxx>
### Diffstat output
./drivers/md/raid5.c | 61 +++++++++++++++++++++++++++++++++++++++----
./include/linux/raid/raid5.h | 2 +
2 files changed, 58 insertions(+), 5 deletions(-)
diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c
--- ./drivers/md/raid5.c~current~ 2005-09-16 12:21:24.000000000 +1000
+++ ./drivers/md/raid5.c 2005-09-16 12:57:12.000000000 +1000
@@ -349,7 +349,7 @@ static void shrink_stripes(raid5_conf_t
conf->slab_cache = NULL;
}
-static int raid5_end_read_request (struct bio * bi, unsigned int bytes_done,
+static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
int error)
{
struct stripe_head *sh = bi->bi_private;
@@ -401,10 +401,27 @@ static int raid5_end_read_request (struc
}
#else
set_bit(R5_UPTODATE, &sh->dev[i].flags);
-#endif
+#endif
+ if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+ printk("R5: read error corrected!!\n");
+ clear_bit(R5_ReadError, &sh->dev[i].flags);
+ clear_bit(R5_ReWrite, &sh->dev[i].flags);
+ }
} else {
- md_error(conf->mddev, conf->disks[i].rdev);
clear_bit(R5_UPTODATE, &sh->dev[i].flags);
+ if (conf->mddev->degraded) {
+ printk("R5: read error not correctable.\n");
+ clear_bit(R5_ReadError, &sh->dev[i].flags);
+ clear_bit(R5_ReWrite, &sh->dev[i].flags);
+ md_error(conf->mddev, conf->disks[i].rdev);
+ } else if (test_bit(R5_ReWrite, &sh->dev[i].flags)) {
+ /* Oh, no!!! */
+ printk("R5: read error NOT corrected!!\n");
+ clear_bit(R5_ReadError, &sh->dev[i].flags);
+ clear_bit(R5_ReWrite, &sh->dev[i].flags);
+ md_error(conf->mddev, conf->disks[i].rdev);
+ } else
+ set_bit(R5_ReadError, &sh->dev[i].flags);
}
rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
#if 0
@@ -966,6 +983,12 @@ static void handle_stripe(struct stripe_
if (dev->written) written++;
rdev = conf->disks[i].rdev; /* FIXME, should I be looking rdev */
if (!rdev || !rdev->in_sync) {
+ /* The ReadError flag wil just be confusing now */
+ clear_bit(R5_ReadError, &dev->flags);
+ clear_bit(R5_ReWrite, &dev->flags);
+ }
+ if (!rdev || !rdev->in_sync
+ || test_bit(R5_ReadError, &dev->flags)) {
failed++;
failed_num = i;
} else
@@ -980,6 +1003,14 @@ static void handle_stripe(struct stripe_
if (failed > 1 && to_read+to_write+written) {
for (i=disks; i--; ) {
int bitmap_end = 0;
+
+ if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+ mdk_rdev_t *rdev = conf->disks[i].rdev;
+ if (rdev && rdev->in_sync)
+ /* multiple read failures in one stripe */
+ md_error(conf->mddev, rdev);
+ }
+
spin_lock_irq(&conf->device_lock);
/* fail all writes first */
bi = sh->dev[i].towrite;
@@ -1015,7 +1046,8 @@ static void handle_stripe(struct stripe_
}
/* fail any reads if this device is non-operational */
- if (!test_bit(R5_Insync, &sh->dev[i].flags)) {
+ if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+ test_bit(R5_ReadError, &sh->dev[i].flags)) {
bi = sh->dev[i].toread;
sh->dev[i].toread = NULL;
if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
@@ -1274,7 +1306,26 @@ static void handle_stripe(struct stripe_
md_done_sync(conf->mddev, STRIPE_SECTORS,1);
clear_bit(STRIPE_SYNCING, &sh->state);
}
-
+
+ /* If the failed drive is just a ReadError, then we might need to progress
+ * the repair/check process
+ */
+ if (failed == 1 && test_bit(R5_ReadError, &sh->dev[failed_num].flags)
+ && !test_bit(R5_LOCKED, &sh->dev[failed_num].flags)
+ && test_bit(R5_UPTODATE, &sh->dev[failed_num].flags)
+ ) {
+ dev = &sh->dev[failed_num];
+ if (!test_bit(R5_ReWrite, &dev->flags)) {
+ set_bit(R5_Wantwrite, &dev->flags);
+ set_bit(R5_ReWrite, &dev->flags);
+ set_bit(R5_LOCKED, &dev->flags);
+ } else {
+ /* let's read it back */
+ set_bit(R5_Wantread, &dev->flags);
+ set_bit(R5_LOCKED, &dev->flags);
+ }
+ }
+
spin_unlock(&sh->lock);
while ((bi=return_bi)) {
diff ./include/linux/raid/raid5.h~current~ ./include/linux/raid/raid5.h
--- ./include/linux/raid/raid5.h~current~ 2005-09-16 12:21:24.000000000 +1000
+++ ./include/linux/raid/raid5.h 2005-09-16 12:55:51.000000000 +1000
@@ -154,6 +154,8 @@ struct stripe_head {
#define R5_Wantwrite 5
#define R5_Syncio 6 /* this io need to be accounted as resync io */
#define R5_Overlap 7 /* There is a pending overlapping request on this block */
+#define R5_ReadError 8 /* seen a read error here recently */
+#define R5_ReWrite 9 /* have tried to over-write the readerror */
/*
* Write method
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
