From: NeilBrown version-1 superblocks are not (normally) 4K long, and can be of variable size. Writing the full 4K can cause corruption (but only in non-default configurations). With this patch the super-block-flavour can choose a size to read, and set a size to write based on what it finds. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton --- drivers/md/md.c | 20 +++++++++++++++----- include/linux/raid/md_k.h | 1 + 2 files changed, 16 insertions(+), 5 deletions(-) diff -puN drivers/md/md.c~md-limit-size-of-sb-read-written-to-appropriate-amount drivers/md/md.c --- devel/drivers/md/md.c~md-limit-size-of-sb-read-written-to-appropriate-amount 2005-08-29 23:44:25.000000000 -0700 +++ devel-akpm/drivers/md/md.c 2005-08-29 23:44:26.000000000 -0700 @@ -393,7 +393,7 @@ int sync_page_io(struct block_device *bd return ret; } -static int read_disk_sb(mdk_rdev_t * rdev) +static int read_disk_sb(mdk_rdev_t * rdev, int size) { char b[BDEVNAME_SIZE]; if (!rdev->sb_page) { @@ -404,7 +404,7 @@ static int read_disk_sb(mdk_rdev_t * rde return 0; - if (!sync_page_io(rdev->bdev, rdev->sb_offset<<1, MD_SB_BYTES, rdev->sb_page, READ)) + if (!sync_page_io(rdev->bdev, rdev->sb_offset<<1, size, rdev->sb_page, READ)) goto fail; rdev->sb_loaded = 1; return 0; @@ -531,7 +531,7 @@ static int super_90_load(mdk_rdev_t *rde sb_offset = calc_dev_sboffset(rdev->bdev); rdev->sb_offset = sb_offset; - ret = read_disk_sb(rdev); + ret = read_disk_sb(rdev, MD_SB_BYTES); if (ret) return ret; ret = -EINVAL; @@ -564,6 +564,7 @@ static int super_90_load(mdk_rdev_t *rde rdev->preferred_minor = sb->md_minor; rdev->data_offset = 0; + rdev->sb_size = MD_SB_BYTES; if (sb->level == LEVEL_MULTIPATH) rdev->desc_nr = -1; @@ -837,6 +838,7 @@ static int super_1_load(mdk_rdev_t *rdev int ret; sector_t sb_offset; char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE]; + int bmask; /* * Calculate the position of the superblock. @@ -865,7 +867,10 @@ static int super_1_load(mdk_rdev_t *rdev } rdev->sb_offset = sb_offset; - ret = read_disk_sb(rdev); + /* superblock is rarely larger than 1K, but it can be larger, + * and it is safe to read 4k, so we do that + */ + ret = read_disk_sb(rdev, 4096); if (ret) return ret; @@ -891,6 +896,11 @@ static int super_1_load(mdk_rdev_t *rdev rdev->preferred_minor = 0xffff; rdev->data_offset = le64_to_cpu(sb->data_offset); + rdev->sb_size = le32_to_cpu(sb->max_dev) * 2 + 256; + bmask = block_size(rdev->bdev)-1; + if (rdev->sb_size & bmask) + rdev-> sb_size = (rdev->sb_size | bmask)+1; + if (refdev == 0) return 1; else { @@ -1375,7 +1385,7 @@ repeat: dprintk("%s ", bdevname(rdev->bdev,b)); if (!rdev->faulty) { md_super_write(mddev,rdev, - rdev->sb_offset<<1, MD_SB_BYTES, + rdev->sb_offset<<1, rdev->sb_size, rdev->sb_page); dprintk(KERN_INFO "(write) %s's sb offset: %llu\n", bdevname(rdev->bdev,b), diff -puN include/linux/raid/md_k.h~md-limit-size-of-sb-read-written-to-appropriate-amount include/linux/raid/md_k.h --- devel/include/linux/raid/md_k.h~md-limit-size-of-sb-read-written-to-appropriate-amount 2005-08-29 23:44:25.000000000 -0700 +++ devel-akpm/include/linux/raid/md_k.h 2005-08-29 23:44:26.000000000 -0700 @@ -102,6 +102,7 @@ struct mdk_rdev_s int sb_loaded; sector_t data_offset; /* start of data in array */ sector_t sb_offset; + int sb_size; /* bytes in the superblock */ int preferred_minor; /* autorun support */ /* A device can be in one of three states based on two flags: _