third_party_littlefs/tests/test_alloc.toml

# allocator tests
# note for these to work there are a number constraints on the device geometry
if = 'LFS_BLOCK_CYCLES == -1'

[[case]] # parallel allocation test
define.FILES = 3
define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-6)) / FILES)'
code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};
    lfs_file_t files[FILES];

    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "breakfast") => 0;
    lfs_unmount(&lfs) => 0;

    lfs_mount(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &files[n], path,
                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
    }
    for (int n = 0; n < FILES; n++) {
        size = strlen(names[n]);
        for (lfs_size_t i = 0; i < SIZE; i += size) {
            lfs_file_write(&lfs, &files[n], names[n], size) => size;
        }
    }
    for (int n = 0; n < FILES; n++) {
        lfs_file_close(&lfs, &files[n]) => 0;
    }
    lfs_unmount(&lfs) => 0;

    lfs_mount(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
        size = strlen(names[n]);
        for (lfs_size_t i = 0; i < SIZE; i += size) {
            lfs_file_read(&lfs, &file, buffer, size) => size;
            assert(memcmp(buffer, names[n], size) == 0);
        }
        lfs_file_close(&lfs, &file) => 0;
    }
    lfs_unmount(&lfs) => 0;
'''

[[case]] # serial allocation test
define.FILES = 3
define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-6)) / FILES)'
code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};

    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "breakfast") => 0;
    lfs_unmount(&lfs) => 0;

    for (int n = 0; n < FILES; n++) {
        lfs_mount(&lfs, &cfg) => 0;
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path,
                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
        size = strlen(names[n]);
        memcpy(buffer, names[n], size);
        for (int i = 0; i < SIZE; i += size) {
            lfs_file_write(&lfs, &file, buffer, size) => size;
        }
        lfs_file_close(&lfs, &file) => 0;
        lfs_unmount(&lfs) => 0;
    }

    lfs_mount(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
        size = strlen(names[n]);
        for (int i = 0; i < SIZE; i += size) {
            lfs_file_read(&lfs, &file, buffer, size) => size;
            assert(memcmp(buffer, names[n], size) == 0);
        }
        lfs_file_close(&lfs, &file) => 0;
    }
    lfs_unmount(&lfs) => 0;
'''

[[case]] # parallel allocation reuse test
define.FILES = 3
define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-6)) / FILES)'
define.CYCLES = [1, 10]
code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};
    lfs_file_t files[FILES];

    lfs_format(&lfs, &cfg) => 0;

    for (int c = 0; c < CYCLES; c++) {
        lfs_mount(&lfs, &cfg) => 0;
        lfs_mkdir(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;

        lfs_mount(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &files[n], path,
                    LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
        }
        for (int n = 0; n < FILES; n++) {
            size = strlen(names[n]);
            for (int i = 0; i < SIZE; i += size) {
                lfs_file_write(&lfs, &files[n], names[n], size) => size;
            }
        }
        for (int n = 0; n < FILES; n++) {
            lfs_file_close(&lfs, &files[n]) => 0;
        }
        lfs_unmount(&lfs) => 0;

        lfs_mount(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
            size = strlen(names[n]);
            for (int i = 0; i < SIZE; i += size) {
                lfs_file_read(&lfs, &file, buffer, size) => size;
                assert(memcmp(buffer, names[n], size) == 0);
            }
            lfs_file_close(&lfs, &file) => 0;
        }
        lfs_unmount(&lfs) => 0;

        lfs_mount(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_remove(&lfs, path) => 0;
        }
        lfs_remove(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;
    }
'''

[[case]] # serial allocation reuse test
define.FILES = 3
define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-6)) / FILES)'
define.CYCLES = [1, 10]
code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};

    lfs_format(&lfs, &cfg) => 0;

    for (int c = 0; c < CYCLES; c++) {
        lfs_mount(&lfs, &cfg) => 0;
        lfs_mkdir(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;

        for (int n = 0; n < FILES; n++) {
            lfs_mount(&lfs, &cfg) => 0;
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path,
                    LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
            size = strlen(names[n]);
            memcpy(buffer, names[n], size);
            for (int i = 0; i < SIZE; i += size) {
                lfs_file_write(&lfs, &file, buffer, size) => size;
            }
            lfs_file_close(&lfs, &file) => 0;
            lfs_unmount(&lfs) => 0;
        }

        lfs_mount(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
            size = strlen(names[n]);
            for (int i = 0; i < SIZE; i += size) {
                lfs_file_read(&lfs, &file, buffer, size) => size;
                assert(memcmp(buffer, names[n], size) == 0);
            }
            lfs_file_close(&lfs, &file) => 0;
        }
        lfs_unmount(&lfs) => 0;

        lfs_mount(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_remove(&lfs, path) => 0;
        }
        lfs_remove(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;
    }
'''

[[case]] # exhaustion test
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("exhaustion");
    memcpy(buffer, "exhaustion", size);
    lfs_file_write(&lfs, &file, buffer, size) => size;
    lfs_file_sync(&lfs, &file) => 0;

    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    lfs_ssize_t res;
    while (true) {
        res = lfs_file_write(&lfs, &file, buffer, size);
        if (res < 0) {
            break;
        }

        res => size;
    }
    res => LFS_ERR_NOSPC;

    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

    lfs_mount(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_RDONLY);
    size = strlen("exhaustion");
    lfs_file_size(&lfs, &file) => size;
    lfs_file_read(&lfs, &file, buffer, size) => size;
    memcmp(buffer, "exhaustion", size) => 0;
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
'''

[[case]] # exhaustion wraparound test
define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-4)) / 3)'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    lfs_file_open(&lfs, &file, "padding", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("buffering");
    memcpy(buffer, "buffering", size);
    for (int i = 0; i < SIZE; i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;
    lfs_remove(&lfs, "padding") => 0;

    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("exhaustion");
    memcpy(buffer, "exhaustion", size);
    lfs_file_write(&lfs, &file, buffer, size) => size;
    lfs_file_sync(&lfs, &file) => 0;

    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    lfs_ssize_t res;
    while (true) {
        res = lfs_file_write(&lfs, &file, buffer, size);
        if (res < 0) {
            break;
        }

        res => size;
    }
    res => LFS_ERR_NOSPC;

    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

    lfs_mount(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_RDONLY);
    size = strlen("exhaustion");
    lfs_file_size(&lfs, &file) => size;
    lfs_file_read(&lfs, &file, buffer, size) => size;
    memcmp(buffer, "exhaustion", size) => 0;
    lfs_file_close(&lfs, &file) => 0;
    lfs_remove(&lfs, "exhaustion") => 0;
    lfs_unmount(&lfs) => 0;
'''

[[case]] # dir exhaustion test
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // find out max file size
    lfs_mkdir(&lfs, "exhaustiondir") => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    int count = 0;
    while (true) {
        err = lfs_file_write(&lfs, &file, buffer, size);
        if (err < 0) {
            break;
        }

        count += 1;
    }
    err => LFS_ERR_NOSPC;
    lfs_file_close(&lfs, &file) => 0;

    lfs_remove(&lfs, "exhaustion") => 0;
    lfs_remove(&lfs, "exhaustiondir") => 0;

    // see if dir fits with max file size
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    for (int i = 0; i < count; i++) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_mkdir(&lfs, "exhaustiondir") => 0;
    lfs_remove(&lfs, "exhaustiondir") => 0;
    lfs_remove(&lfs, "exhaustion") => 0;

    // see if dir fits with > max file size
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    for (int i = 0; i < count+1; i++) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_mkdir(&lfs, "exhaustiondir") => LFS_ERR_NOSPC;

    lfs_remove(&lfs, "exhaustion") => 0;
    lfs_unmount(&lfs) => 0;
'''

[[case]] # what if we have a bad block during an allocation scan?
in = "lfs.c"
define.LFS_ERASE_CYCLES = 0xffffffff
define.LFS_BADBLOCK_BEHAVIOR = 'LFS_TESTBD_BADBLOCK_READERROR'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;
    // first fill to exhaustion to find available space
    lfs_file_open(&lfs, &file, "pacman", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "waka");
    size = strlen("waka");
    lfs_size_t filesize = 0;
    while (true) {
        lfs_ssize_t res = lfs_file_write(&lfs, &file, buffer, size);
        assert(res == (lfs_ssize_t)size || res == LFS_ERR_NOSPC);
        if (res == LFS_ERR_NOSPC) {
            break;
        }
        filesize += size;
    }
    lfs_file_close(&lfs, &file) => 0;
    // now fill all but a couple of blocks of the filesystem with data
    filesize -= 3*LFS_BLOCK_SIZE;
    lfs_file_open(&lfs, &file, "pacman", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "waka");
    size = strlen("waka");
    for (lfs_size_t i = 0; i < filesize/size; i++) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;
    // also save head of file so we can error during lookahead scan
    lfs_block_t fileblock = file.ctz.head;
    lfs_unmount(&lfs) => 0;

    // remount to force an alloc scan
    lfs_mount(&lfs, &cfg) => 0;

    // but mark the head of our file as a "bad block", this is force our
    // scan to bail early
    lfs_testbd_setwear(&cfg, fileblock, 0xffffffff) => 0;
    lfs_file_open(&lfs, &file, "ghost", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "chomp");
    size = strlen("chomp");
    while (true) {
        lfs_ssize_t res = lfs_file_write(&lfs, &file, buffer, size);
        assert(res == (lfs_ssize_t)size || res == LFS_ERR_CORRUPT);
        if (res == LFS_ERR_CORRUPT) {
            break;
        }
    }
    lfs_file_close(&lfs, &file) => 0;

    // now reverse the "bad block" and try to write the file again until we
    // run out of space
    lfs_testbd_setwear(&cfg, fileblock, 0) => 0;
    lfs_file_open(&lfs, &file, "ghost", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "chomp");
    size = strlen("chomp");
    while (true) {
        lfs_ssize_t res = lfs_file_write(&lfs, &file, buffer, size);
        assert(res == (lfs_ssize_t)size || res == LFS_ERR_NOSPC);
        if (res == LFS_ERR_NOSPC) {
            break;
        }
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_unmount(&lfs) => 0;

    // check that the disk isn't hurt
    lfs_mount(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "pacman", LFS_O_RDONLY) => 0;
    strcpy((char*)buffer, "waka");
    size = strlen("waka");
    for (lfs_size_t i = 0; i < filesize/size; i++) {
        uint8_t rbuffer[4];
        lfs_file_read(&lfs, &file, rbuffer, size) => size;
        assert(memcmp(rbuffer, buffer, size) == 0);
    }
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
'''


# Below, I don't like these tests. They're fragile and depend _heavily_
# on the geometry of the block device. But they are valuable. Eventually they
# should be removed and replaced with generalized tests.

[[case]] # chained dir exhaustion test
define.LFS_BLOCK_SIZE = 512
define.LFS_BLOCK_COUNT = 1024
if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // find out max file size
    lfs_mkdir(&lfs, "exhaustiondir") => 0;
    for (int i = 0; i < 10; i++) {
        sprintf(path, "dirwithanexhaustivelylongnameforpadding%d", i);
        lfs_mkdir(&lfs, path) => 0;
    }
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    int count = 0;
    while (true) {
        err = lfs_file_write(&lfs, &file, buffer, size);
        if (err < 0) {
            break;
        }

        count += 1;
    }
    err => LFS_ERR_NOSPC;
    lfs_file_close(&lfs, &file) => 0;

    lfs_remove(&lfs, "exhaustion") => 0;
    lfs_remove(&lfs, "exhaustiondir") => 0;
    for (int i = 0; i < 10; i++) {
        sprintf(path, "dirwithanexhaustivelylongnameforpadding%d", i);
        lfs_remove(&lfs, path) => 0;
    }

    // see that chained dir fails
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    for (int i = 0; i < count+1; i++) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_sync(&lfs, &file) => 0;

    for (int i = 0; i < 10; i++) {
        sprintf(path, "dirwithanexhaustivelylongnameforpadding%d", i);
        lfs_mkdir(&lfs, path) => 0;
    }

    lfs_mkdir(&lfs, "exhaustiondir") => LFS_ERR_NOSPC;

    // shorten file to try a second chained dir
    while (true) {
        err = lfs_mkdir(&lfs, "exhaustiondir");
        if (err != LFS_ERR_NOSPC) {
            break;
        }

        lfs_ssize_t filesize = lfs_file_size(&lfs, &file);
        filesize > 0 => true;

        lfs_file_truncate(&lfs, &file, filesize - size) => 0;
        lfs_file_sync(&lfs, &file) => 0;
    }
    err => 0;

    lfs_mkdir(&lfs, "exhaustiondir2") => LFS_ERR_NOSPC;

    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
'''

[[case]] # split dir test
define.LFS_BLOCK_SIZE = 512
define.LFS_BLOCK_COUNT = 1024
if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // create one block hole for half a directory
    lfs_file_open(&lfs, &file, "bump", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    for (lfs_size_t i = 0; i < cfg.block_size; i += 2) {
        memcpy(&buffer[i], "hi", 2);
    }
    lfs_file_write(&lfs, &file, buffer, cfg.block_size) => cfg.block_size;
    lfs_file_close(&lfs, &file) => 0;

    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < (cfg.block_count-4)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // open hole
    lfs_remove(&lfs, "bump") => 0;

    lfs_mkdir(&lfs, "splitdir") => 0;
    lfs_file_open(&lfs, &file, "splitdir/bump",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    for (lfs_size_t i = 0; i < cfg.block_size; i += 2) {
        memcpy(&buffer[i], "hi", 2);
    }
    lfs_file_write(&lfs, &file, buffer, 2*cfg.block_size) => LFS_ERR_NOSPC;
    lfs_file_close(&lfs, &file) => 0;

    lfs_unmount(&lfs) => 0;
'''

[[case]] # outdated lookahead test
define.LFS_BLOCK_SIZE = 512
define.LFS_BLOCK_COUNT = 1024
if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // fill completely with two files
    lfs_file_open(&lfs, &file, "exhaustion1",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_file_open(&lfs, &file, "exhaustion2",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // rewrite one file
    lfs_file_open(&lfs, &file, "exhaustion1",
            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
    lfs_file_sync(&lfs, &file) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    // rewrite second file, this requires lookahead does not
    // use old population
    lfs_file_open(&lfs, &file, "exhaustion2",
            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
    lfs_file_sync(&lfs, &file) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_unmount(&lfs) => 0;
'''

[[case]] # outdated lookahead and split dir test
define.LFS_BLOCK_SIZE = 512
define.LFS_BLOCK_COUNT = 1024
if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
code = '''
    lfs_format(&lfs, &cfg) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // fill completely with two files
    lfs_file_open(&lfs, &file, "exhaustion1",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    lfs_file_open(&lfs, &file, "exhaustion2",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
    lfs_mount(&lfs, &cfg) => 0;

    // rewrite one file with a hole of one block
    lfs_file_open(&lfs, &file, "exhaustion1",
            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
    lfs_file_sync(&lfs, &file) => 0;
    size = strlen("blahblahblahblah");
    memcpy(buffer, "blahblahblahblah", size);
    for (lfs_size_t i = 0;
            i < ((cfg.block_count-2)/2 - 1)*(cfg.block_size-8);
            i += size) {
        lfs_file_write(&lfs, &file, buffer, size) => size;
    }
    lfs_file_close(&lfs, &file) => 0;

    // try to allocate a directory, should fail!
    lfs_mkdir(&lfs, "split") => LFS_ERR_NOSPC;

    // file should not fail
    lfs_file_open(&lfs, &file, "notasplit",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_write(&lfs, &file, "hi", 2) => 2;
    lfs_file_close(&lfs, &file) => 0;

    lfs_unmount(&lfs) => 0;
'''