From: NeilBrown The remainder of this batch implements raid5 reshaping. Currently the only shape change that is supported is added a device, but it is envisioned that changing the chunksize and layout will also be supported, as well as changing the level (e.g. 1->5, 5->6). The reshape process naturally has to move all of the data in the array, and so should be used with caution. It is believed to work, and some testing does support this, but wider testing would be great for increasing my confidence. You will need a version of mdadm newer than 2.3.1 to make use of raid5 growth. This is because mdadm need to take a copy of a 'critical section' at the start of the array incase there is a crash at an awkward moment. On restart, mdadm will restore the critical section and allow reshape to continue. I hope to release a 2.4-pre by early next week - it still needs a little more polishing. This patch: Previously the array of disk information was included in the raid5 'conf' structure which was allocated to an appropriate size. This makes it awkward to change the size of that array. So we split it off into a separate kmalloced array which will require a little extra indexing, but is much easier to grow. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton --- drivers/md/raid5.c | 10 +++++++--- drivers/md/raid6main.c | 10 +++++++--- include/linux/raid/raid5.h | 2 +- 3 files changed, 15 insertions(+), 7 deletions(-) diff -puN drivers/md/raid5.c~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow drivers/md/raid5.c --- devel/drivers/md/raid5.c~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow 2006-03-16 23:32:27.000000000 -0800 +++ devel-akpm/drivers/md/raid5.c 2006-03-16 23:32:27.000000000 -0800 @@ -1822,11 +1822,13 @@ static int run(mddev_t *mddev) return -EIO; } - mddev->private = kzalloc(sizeof (raid5_conf_t) - + mddev->raid_disks * sizeof(struct disk_info), - GFP_KERNEL); + mddev->private = kzalloc(sizeof (raid5_conf_t), GFP_KERNEL); if ((conf = mddev->private) == NULL) goto abort; + conf->disks = kzalloc(mddev->raid_disks * sizeof(struct disk_info), + GFP_KERNEL); + if (!conf->disks) + goto abort; conf->mddev = mddev; @@ -1966,6 +1968,7 @@ static int run(mddev_t *mddev) abort: if (conf) { print_raid5_conf(conf); + kfree(conf->disks); kfree(conf->stripe_hashtbl); kfree(conf); } @@ -1986,6 +1989,7 @@ static int stop(mddev_t *mddev) kfree(conf->stripe_hashtbl); blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/ sysfs_remove_group(&mddev->kobj, &raid5_attrs_group); + kfree(conf->disks); kfree(conf); mddev->private = NULL; return 0; diff -puN drivers/md/raid6main.c~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow drivers/md/raid6main.c --- devel/drivers/md/raid6main.c~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow 2006-03-16 23:32:27.000000000 -0800 +++ devel-akpm/drivers/md/raid6main.c 2006-03-16 23:32:27.000000000 -0800 @@ -2006,11 +2006,14 @@ static int run(mddev_t *mddev) return -EIO; } - mddev->private = kzalloc(sizeof (raid6_conf_t) - + mddev->raid_disks * sizeof(struct disk_info), - GFP_KERNEL); + mddev->private = kzalloc(sizeof (raid6_conf_t), GFP_KERNEL); if ((conf = mddev->private) == NULL) goto abort; + conf->disks = kzalloc(mddev->raid_disks * sizeof(struct disk_info), + GFP_KERNEL); + if (!conf->disks) + goto abort; + conf->mddev = mddev; if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL) @@ -2158,6 +2161,7 @@ abort: print_raid6_conf(conf); safe_put_page(conf->spare_page); kfree(conf->stripe_hashtbl); + kfree(conf->disks); kfree(conf); } mddev->private = NULL; diff -puN include/linux/raid/raid5.h~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow include/linux/raid/raid5.h --- devel/include/linux/raid/raid5.h~md-split-disks-array-out-of-raid5-conf-structure-so-it-is-easier-to-grow 2006-03-16 23:32:27.000000000 -0800 +++ devel-akpm/include/linux/raid/raid5.h 2006-03-16 23:32:27.000000000 -0800 @@ -240,7 +240,7 @@ struct raid5_private_data { * waiting for 25% to be free */ spinlock_t device_lock; - struct disk_info disks[0]; + struct disk_info *disks; }; typedef struct raid5_private_data raid5_conf_t; _