diff options
| -rw-r--r-- | Documentation/md.txt | 24 | ||||
| -rw-r--r-- | drivers/md/md.c | 4 | ||||
| -rw-r--r-- | drivers/md/raid5.c | 15 | ||||
| -rw-r--r-- | drivers/md/raid6main.c | 13 | ||||
| -rw-r--r-- | include/linux/raid/md_k.h | 1 |
5 files changed, 49 insertions, 8 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt index 23e6cce40f9c..1dd0fb6021cf 100644 --- a/Documentation/md.txt +++ b/Documentation/md.txt @@ -51,6 +51,30 @@ superblock can be autodetected and run at boot time. The kernel parameter "raid=partitionable" (or "raid=part") means that all auto-detected arrays are assembled as partitionable. +Boot time assembly of degraded/dirty arrays +------------------------------------------- + +If a raid5 or raid6 array is both dirty and degraded, it could have +undetectable data corruption. This is because the fact that it is +'dirty' means that the parity cannot be trusted, and the fact that it +is degraded means that some datablocks are missing and cannot reliably +be reconstructed (due to no parity). + +For this reason, md will normally refuse to start such an array. This +requires the sysadmin to take action to explicitly start the array +desipite possible corruption. This is normally done with + mdadm --assemble --force .... + +This option is not really available if the array has the root +filesystem on it. In order to support this booting from such an +array, md supports a module parameter "start_dirty_degraded" which, +when set to 1, bypassed the checks and will allows dirty degraded +arrays to be started. + +So, to boot with a root filesystem of a dirty degraded raid[56], use + + md-mod.start_dirty_degraded=1 + Superblock formats ------------------ diff --git a/drivers/md/md.c b/drivers/md/md.c index 8175a2a222da..b4fb7247b3ed 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -1937,6 +1937,7 @@ static void md_safemode_timeout(unsigned long data) md_wakeup_thread(mddev->thread); } +static int start_dirty_degraded; static int do_md_run(mddev_t * mddev) { @@ -2048,6 +2049,7 @@ static int do_md_run(mddev_t * mddev) mddev->recovery = 0; mddev->resync_max_sectors = mddev->size << 1; /* may be over-ridden by personality */ mddev->barriers_work = 1; + mddev->ok_start_degraded = start_dirty_degraded; if (start_readonly) mddev->ro = 2; /* read-only, but switch on first write */ @@ -4509,6 +4511,8 @@ static int set_ro(const char *val, struct kernel_param *kp) } module_param_call(start_ro, set_ro, get_ro, NULL, 0600); +module_param(start_dirty_degraded, int, 0644); + EXPORT_SYMBOL(register_md_personality); EXPORT_SYMBOL(unregister_md_personality); diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 334ff7a07283..53a0f2ce76c8 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -1904,10 +1904,17 @@ static int run(mddev_t *mddev) if (mddev->degraded == 1 && mddev->recovery_cp != MaxSector) { - printk(KERN_ERR - "raid5: cannot start dirty degraded array for %s\n", - mdname(mddev)); - goto abort; + if (mddev->ok_start_degraded) + printk(KERN_WARNING + "raid5: starting dirty degraded array: %s" + "- data corruption possible.\n", + mdname(mddev)); + else { + printk(KERN_ERR + "raid5: cannot start dirty degraded array for %s\n", + mdname(mddev)); + goto abort; + } } { diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c index 0000d162d198..9ac6dcd55127 100644 --- a/drivers/md/raid6main.c +++ b/drivers/md/raid6main.c @@ -1929,13 +1929,18 @@ static int run(mddev_t *mddev) goto abort; } -#if 0 /* FIX: For now */ if (mddev->degraded > 0 && mddev->recovery_cp != MaxSector) { - printk(KERN_ERR "raid6: cannot start dirty degraded array for %s\n", mdname(mddev)); - goto abort; + if (mddev->ok_start_degraded) + printk(KERN_WARNING "raid6: starting dirty degraded array:%s" + "- data corruption possible.\n", + mdname(mddev)); + else { + printk(KERN_ERR "raid6: cannot start dirty degraded array" + " for %s\n", mdname(mddev)); + goto abort; + } } -#endif { mddev->thread = md_register_thread(raid6d, mddev, "%s_raid6"); diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h index 46629a275ba9..1dd587b5975a 100644 --- a/include/linux/raid/md_k.h +++ b/include/linux/raid/md_k.h @@ -183,6 +183,7 @@ struct mddev_s sector_t resync_mismatches; /* count of sectors where * parity/replica mismatch found */ + int ok_start_degraded; /* recovery/resync flags * NEEDED: we might need to start a resync/recover * RUNNING: a thread is running, or about to be started |