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[PATCH] md: better handling of readerrors with raid5.

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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.

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@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown 2005-11-08 21:39:22 -08:00 committed by Linus Torvalds
parent 703ebe86a9
commit 4e5314b56a
2 changed files with 58 additions and 5 deletions
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61
drivers/md/raid5.c
View file

@ -349,7 +349,7 @@ static void shrink_stripes(raid5_conf_t *conf)
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 (struct bio * bi, unsigned int bytes_done,
}
#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_head *sh)
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_head *sh)
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_head *sh)
}
/* 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_head *sh)
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)) {

2
include/linux/raid/raid5.h
View file

@ -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