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Changed how we write out superblock to use append

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Making the superblock look like "just another entry" allows us to treat
the superblock like "just another entry" and reuse a decent amount of
logic that would otherwise only be used a format and mount time. In this
case we can use append to write out the superblock like it was creating
a new entry on the filesystem.
This commit is contained in:
Christopher Haster
2018-03-23 16:11:36 -05:00
parent 701e4fa438
commit d0e0453651
4 changed files with 45 additions and 51 deletions
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75
lfs.c
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@@ -2372,38 +2372,40 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
lfs->root[0] = root.pair[0];
lfs->root[1] = root.pair[1];
superdir.d.tail[0] = lfs->root[0];
superdir.d.tail[1] = lfs->root[1];
// write superblocks
lfs_superblock_t superblock = {
.d.type = LFS_STRUCT_DIR | LFS_TYPE_SUPERBLOCK,
.d.elen = sizeof(superblock.d) - sizeof(superblock.d.magic) - 4,
.d.nlen = sizeof(superblock.d.magic),
.d.version = LFS_DISK_VERSION,
.d.magic = {"littlefs"},
.d.block_size = lfs->cfg->block_size,
.d.block_count = lfs->cfg->block_count,
.d.root = {lfs->root[0], lfs->root[1]},
};
superdir.d.tail[0] = root.pair[0];
superdir.d.tail[1] = root.pair[1];
superdir.d.size = sizeof(superdir.d) + sizeof(superblock.d) + 4;
// write one superblocks
lfs_superblock_t superblock;
superblock.d.version = LFS_DISK_VERSION,
superblock.d.root[0] = lfs->root[0];
superblock.d.root[1] = lfs->root[1];
superblock.d.block_size = lfs->cfg->block_size;
superblock.d.block_count = lfs->cfg->block_count;
// write both pairs to be safe
lfs_entry_t superentry;
superentry.d.type = LFS_STRUCT_DIR | LFS_TYPE_SUPERBLOCK;
superentry.d.elen = sizeof(superblock.d);
superentry.d.alen = 0;
superentry.d.nlen = strlen("littlefs");
superentry.off = sizeof(superdir.d);
superentry.size = 4 + superentry.d.elen +
superentry.d.alen + superentry.d.nlen;
lfs_entry_tole32(&superentry.d);
lfs_superblock_tole32(&superblock.d);
bool valid = false;
for (int i = 0; i < 2; i++) {
err = lfs_dir_commit(lfs, &superdir, &(struct lfs_region){
sizeof(superdir.d), 0,
lfs_commit_mem, &superblock.d, sizeof(superblock.d)});
if (err && err != LFS_ERR_CORRUPT) {
return err;
}
valid = valid || !err;
}
if (!valid) {
return LFS_ERR_CORRUPT;
err = lfs_dir_append(lfs, &superdir, &superentry,
&(struct lfs_region){
0, +4,
lfs_commit_mem, &superentry.d, 4,
&(struct lfs_region){
0, +sizeof(superblock.d),
lfs_commit_mem, &superblock.d, sizeof(superblock.d),
&(struct lfs_region){
0, +superentry.d.nlen,
lfs_commit_mem, "littlefs", superentry.d.nlen}}});
if (err) {
return err;
}
// sanity check that fetch works
@@ -2412,7 +2414,6 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
return err;
}
lfs_alloc_ack(lfs);
return lfs_deinit(lfs);
}
@@ -2431,25 +2432,33 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
// load superblock
lfs_dir_t dir;
lfs_superblock_t superblock;
char magic[8];
err = lfs_dir_fetch(lfs, &dir, (const lfs_block_t[2]){0, 1});
if (err && err != LFS_ERR_CORRUPT) {
return err;
}
if (!err) {
err = lfs_bd_read(lfs, dir.pair[0], sizeof(dir.d),
err = lfs_bd_read(lfs, dir.pair[0], sizeof(dir.d)+4,
&superblock.d, sizeof(superblock.d));
lfs_superblock_fromle32(&superblock.d);
if (err) {
return err;
}
err = lfs_bd_read(lfs, dir.pair[0],
sizeof(dir.d) + 4 + sizeof(superblock.d),
magic, sizeof(magic));
if (err) {
return err;
}
lfs->root[0] = superblock.d.root[0];
lfs->root[1] = superblock.d.root[1];
}
if (err || memcmp(superblock.d.magic, "littlefs", 8) != 0) {
LFS_ERROR("Invalid superblock at %d %d", 0, 1);
if (err || memcmp(magic, "littlefs", 8) != 0) {
LFS_ERROR("Invalid superblock at %d %d", dir.pair[0], dir.pair[1]);
return LFS_ERR_CORRUPT;
}