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Add config flag to disable block count check on mount #1096

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Add config flag to disable block count check on mount #1096

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10 changes: 8 additions & 2 deletions lfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4592,15 +4592,21 @@ static int lfs_mount_(lfs_t *lfs, const struct lfs_config *cfg) {
}

// this is where we get the block_count from disk if block_count=0
if (lfs->cfg->block_count

if ((lfs->cfg->flags & LFS_CFG_DISABLE_BLOCK_COUNT_CHECK) == 0
&& lfs->cfg->block_count
&& superblock.block_count != lfs->cfg->block_count) {
LFS_ERROR("Invalid block count (%"PRIu32" != %"PRIu32")",
superblock.block_count, lfs->cfg->block_count);
err = LFS_ERR_INVAL;
goto cleanup;
}

lfs->block_count = superblock.block_count;
if (lfs->cfg->block_count) {
lfs->block_count = lfs->cfg->block_count;
} else {
lfs->block_count = superblock.block_count;
}

if (superblock.block_size != lfs->cfg->block_size) {
LFS_ERROR("Invalid block size (%"PRIu32" != %"PRIu32")",
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9 changes: 9 additions & 0 deletions lfs.h
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Expand Up @@ -283,6 +283,11 @@ struct lfs_config {
// Set to -1 to disable inlined files.
lfs_size_t inline_max;

// Configuration flags for the filesystem
//
// See variants of lfs_fs_flags
uint32_t flags;

#ifdef LFS_MULTIVERSION
// On-disk version to use when writing in the form of 16-bit major version
// + 16-bit minor version. This limiting metadata to what is supported by
Expand All @@ -292,6 +297,10 @@ struct lfs_config {
#endif
};

enum lfs_fs_flags {
LFS_CFG_DISABLE_BLOCK_COUNT_CHECK = 1, // Allow mounting a filesystem with a different block count in the config and the superblock
};

// File info structure
struct lfs_info {
// Type of the file, either LFS_TYPE_REG or LFS_TYPE_DIR
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6 changes: 6 additions & 0 deletions tests/test_superblocks.toml
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Expand Up @@ -465,7 +465,13 @@ code = '''
lfs_unmount(&lfs) => 0;

if (KNOWN_BLOCK_COUNT) {
cfg->block_count = BLOCK_COUNT_2 + 1;
lfs_mount(&lfs, cfg) => LFS_ERR_INVAL;
cfg->flags |= LFS_CFG_DISABLE_BLOCK_COUNT_CHECK;
lfs_mount(&lfs, cfg) => 0;
lfs_unmount(&lfs) => 0;
cfg->block_count = BLOCK_COUNT_2;
cfg->flags &= ~LFS_CFG_DISABLE_BLOCK_COUNT_CHECK;
} else {
cfg->block_count = 0;
}
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