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Write a backup superblock at the end of the disk

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Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2021-05-27 21:12:17 -04:00
parent 27d75d929f
commit ea750088b0
1 changed files with 21 additions and 6 deletions
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27
libbcachefs.c
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@ -38,7 +38,7 @@ static u64 min_size(unsigned bucket_size)
static void init_layout(struct bch_sb_layout *l,
unsigned block_size,
unsigned sb_size,
u64 start, u64 end)
u64 sb_start, u64 sb_end)
{
unsigned i;
@ -51,14 +51,14 @@ static void init_layout(struct bch_sb_layout *l,
/* Create two superblocks in the allowed range: */
for (i = 0; i < l->nr_superblocks; i++) {
if (start != BCH_SB_SECTOR)
start = round_up(start, block_size);
if (sb_start != BCH_SB_SECTOR)
sb_start = round_up(sb_start, block_size);
l->sb_offset[i] = cpu_to_le64(start);
start += sb_size;
l->sb_offset[i] = cpu_to_le64(sb_start);
sb_start += sb_size;
}
if (start >= end)
if (sb_start >= sb_end)
die("insufficient space for superblocks");
}
@ -292,6 +292,21 @@ struct bch_sb *bch2_format(struct bch_opt_strs fs_opt_strs,
opts.superblock_size,
i->sb_offset, i->sb_end);
/*
* Also create a backup superblock at the end of the disk:
*
* If we're not creating a superblock at the default offset, it
* means we're being run from the migrate tool and we could be
* overwriting existing data if we write to the end of the disk:
*/
if (i->sb_offset == BCH_SB_SECTOR) {
struct bch_sb_layout *l = &sb.sb->layout;
u64 backup_sb = i->size - (1 << l->sb_max_size_bits);
backup_sb = rounddown(backup_sb, i->bucket_size);
l->sb_offset[l->nr_superblocks++] = cpu_to_le64(backup_sb);
}
if (i->sb_offset == BCH_SB_SECTOR) {
/* Zero start of disk */
static const char zeroes[BCH_SB_SECTOR << 9];