From dd00a99e7a4b739bd41ef4093760efc7e447f963 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 10 May 2007 03:15:50 -0700 Subject: [PATCH] md: avoid a possibility that a read error can wrongly propagate through md/raid1 to a filesystem. When a raid1 has only one working drive, we want read error to propagate up to the filesystem as there is no point failing the last drive in an array. Currently the code perform this check is racy. If a write and a read a both submitted to a device on a 2-drive raid1, and the write fails followed by the read failing, the read will see that there is only one working drive and will pass the failure up, even though the one working drive is actually the *other* one. So, tighten up the locking. Signed-off-by: Neil Brown Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/raid1.c | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-) diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 97ee870b265..3a95cc5e029 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -271,21 +271,25 @@ static int raid1_end_read_request(struct bio *bio, unsigned int bytes_done, int */ update_head_pos(mirror, r1_bio); - if (uptodate || (conf->raid_disks - conf->mddev->degraded) <= 1) { - /* - * Set R1BIO_Uptodate in our master bio, so that - * we will return a good error code for to the higher - * levels even if IO on some other mirrored buffer fails. - * - * The 'master' represents the composite IO operation to - * user-side. So if something waits for IO, then it will - * wait for the 'master' bio. + if (uptodate) + set_bit(R1BIO_Uptodate, &r1_bio->state); + else { + /* If all other devices have failed, we want to return + * the error upwards rather than fail the last device. + * Here we redefine "uptodate" to mean "Don't want to retry" */ - if (uptodate) - set_bit(R1BIO_Uptodate, &r1_bio->state); + unsigned long flags; + spin_lock_irqsave(&conf->device_lock, flags); + if (r1_bio->mddev->degraded == conf->raid_disks || + (r1_bio->mddev->degraded == conf->raid_disks-1 && + !test_bit(Faulty, &conf->mirrors[mirror].rdev->flags))) + uptodate = 1; + spin_unlock_irqrestore(&conf->device_lock, flags); + } + if (uptodate) raid_end_bio_io(r1_bio); - } else { + else { /* * oops, read error: */ @@ -992,13 +996,14 @@ static void error(mddev_t *mddev, mdk_rdev_t *rdev) unsigned long flags; spin_lock_irqsave(&conf->device_lock, flags); mddev->degraded++; + set_bit(Faulty, &rdev->flags); spin_unlock_irqrestore(&conf->device_lock, flags); /* * if recovery is running, make sure it aborts. */ set_bit(MD_RECOVERY_ERR, &mddev->recovery); - } - set_bit(Faulty, &rdev->flags); + } else + set_bit(Faulty, &rdev->flags); set_bit(MD_CHANGE_DEVS, &mddev->flags); printk(KERN_ALERT "raid1: Disk failure on %s, disabling device. \n" " Operation continuing on %d devices\n", -- 2.20.1