On May 29, 2007 22:26 +0100, Daniel Drake wrote:
> The partition in question has a block size of 4096, and mke2fs reports that
> backup superblocks were created on blocks 32768, 98304, 163840, ...
>
> When running e2fsck, get_backup_sb starts by guessing a block size of 1024
> and backup superblock at block 8193. I'm not sure why, but it actually finds
> a superblock at this location, so returns a context with superblock 8193,
> blocksize 1024.
This might be due to the superblock being in the journal at that location...
This would fit right in the 32MB = 8192 block * 4kB block journal default.
I wonder if e2fsck should start by guessing the default blocksize based on
the size of the device, as we might otherwise find old superblocks from
previous fdisk/mke2fs incarnations.
> The following patch solves the problem by discounting superblocks which do
> not meet the currently-sought block size.
> As a result, block 32768 (blocksize=4096) is now used to restore the backup,
> which agrees with the first location that mke2fs listed.
Looks reasonable.
> @@ -453,7 +453,8 @@ blk_t get_backup_sb(e2fsck_t ctx, ext2_f
> if (sb->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC))
> ext2fs_swap_super(sb);
> #endif
> - if (sb->s_magic == EXT2_SUPER_MAGIC) {
> + if (sb->s_magic == EXT2_SUPER_MAGIC &&
> + EXT2_BLOCK_SIZE(sb) == blocksize) {
> ret_sb = superblock;
> if (ctx) {
> ctx->superblock = superblock;
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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