mirror of
				https://github.com/eledio-devices/thirdparty-littlefs.git
				synced 2025-10-31 16:14:16 +01:00 
			
		
		
		
	In writing the initial allocator, I ran into the rather difficult problem of trying to iterate through the entire filesystem cheaply and with only constant memory consumption (which prohibits recursive functions). The solution was to simply thread all directory blocks onto a massive linked-list that spans the entire filesystem. With the linked-list it was easy to create a traverse function for all blocks in use on the filesystem (which has potential for other utility), and add the rudimentary block allocator using a bit-vector. While the linked-list may add complexity (especially where needing to maintain atomic operations), the linked-list helps simplify what is currently the most expensive operation in the filesystem, with no cost to space (the linked-list can reuse the pointers used for chained directory blocks).
		
			
				
	
	
		
			115 lines
		
	
	
		
			2.8 KiB
		
	
	
	
		
			Bash
		
	
	
		
			Executable File
		
	
	
	
	
			
		
		
	
	
			115 lines
		
	
	
		
			2.8 KiB
		
	
	
	
		
			Bash
		
	
	
		
			Executable File
		
	
	
	
	
| #!/bin/bash
 | |
| set -eu
 | |
| 
 | |
| echo "=== Allocator tests ==="
 | |
| rm -rf blocks
 | |
| tests/test.py << TEST
 | |
|     lfs_format(&lfs, &config) => 0;
 | |
| TEST
 | |
| 
 | |
| SIZE=15000
 | |
| 
 | |
| lfs_mkdir() {
 | |
| tests/test.py << TEST
 | |
|     lfs_mount(&lfs, &config) => 0;
 | |
|     lfs_mkdir(&lfs, "$1") => 0;
 | |
|     lfs_unmount(&lfs) => 0;
 | |
| TEST
 | |
| }
 | |
| 
 | |
| lfs_remove() {
 | |
| tests/test.py << TEST
 | |
|     lfs_mount(&lfs, &config) => 0;
 | |
|     lfs_remove(&lfs, "$1/eggs") => 0;
 | |
|     lfs_remove(&lfs, "$1/bacon") => 0;
 | |
|     lfs_remove(&lfs, "$1/pancakes") => 0;
 | |
|     lfs_remove(&lfs, "$1") => 0;
 | |
|     lfs_unmount(&lfs) => 0;
 | |
| TEST
 | |
| }
 | |
| 
 | |
| lfs_alloc_singleproc() {
 | |
| tests/test.py << TEST
 | |
|     const char *names[] = {"bacon", "eggs", "pancakes"};
 | |
|     lfs_mount(&lfs, &config) => 0;
 | |
|     for (int n = 0; n < sizeof(names)/sizeof(names[0]); n++) {
 | |
|         sprintf((char*)buffer, "$1/%s", names[n]);
 | |
|         lfs_file_open(&lfs, &file[n], (char*)buffer,
 | |
|                 LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
 | |
|     }
 | |
|     for (int n = 0; n < sizeof(names)/sizeof(names[0]); n++) {
 | |
|         size = strlen(names[n]);
 | |
|         for (int i = 0; i < $SIZE; i++) {
 | |
|             lfs_file_write(&lfs, &file[n], names[n], size) => size;
 | |
|         }
 | |
|     }
 | |
|     for (int n = 0; n < sizeof(names)/sizeof(names[0]); n++) {
 | |
|         lfs_file_close(&lfs, &file[n]) => 0;
 | |
|     }
 | |
|     lfs_unmount(&lfs) => 0;
 | |
| TEST
 | |
| }
 | |
| 
 | |
| lfs_alloc_multiproc() {
 | |
| for name in bacon eggs pancakes
 | |
| do
 | |
| tests/test.py << TEST
 | |
|     lfs_mount(&lfs, &config) => 0;
 | |
|     lfs_file_open(&lfs, &file[0], "$1/$name",
 | |
|             LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
 | |
|     size = strlen("$name");
 | |
|     memcpy(buffer, "$name", size);
 | |
|     for (int i = 0; i < $SIZE; i++) {
 | |
|         lfs_file_write(&lfs, &file[0], buffer, size) => size;
 | |
|     }
 | |
|     lfs_file_close(&lfs, &file[0]) => 0;
 | |
|     lfs_unmount(&lfs) => 0;
 | |
| TEST
 | |
| done
 | |
| }
 | |
| 
 | |
| lfs_verify() {
 | |
| for name in bacon eggs pancakes
 | |
| do
 | |
| tests/test.py << TEST
 | |
|     lfs_mount(&lfs, &config) => 0;
 | |
|     lfs_file_open(&lfs, &file[0], "$1/$name", LFS_O_RDONLY) => 0;
 | |
|     size = strlen("$name");
 | |
|     for (int i = 0; i < $SIZE; i++) {
 | |
|         lfs_file_read(&lfs, &file[0], buffer, size) => size;
 | |
|         memcmp(buffer, "$name", size) => 0;
 | |
|     }
 | |
|     lfs_file_close(&lfs, &file[0]) => 0;
 | |
|     lfs_unmount(&lfs) => 0;
 | |
| TEST
 | |
| done
 | |
| }
 | |
| 
 | |
| echo "--- Single-process allocation test ---"
 | |
| lfs_mkdir singleproc
 | |
| lfs_alloc_singleproc singleproc
 | |
| lfs_verify singleproc
 | |
| 
 | |
| echo "--- Multi-process allocation test ---"
 | |
| lfs_mkdir multiproc
 | |
| lfs_alloc_multiproc multiproc
 | |
| lfs_verify multiproc
 | |
| lfs_verify singleproc
 | |
| 
 | |
| echo "--- Single-process reuse test ---"
 | |
| lfs_remove singleproc
 | |
| lfs_mkdir singleprocreuse
 | |
| lfs_alloc_singleproc singleprocreuse
 | |
| lfs_verify singleprocreuse
 | |
| lfs_verify multiproc
 | |
| 
 | |
| echo "--- Multi-process reuse test ---"
 | |
| lfs_remove multiproc
 | |
| lfs_mkdir multiprocreuse
 | |
| lfs_alloc_singleproc multiprocreuse
 | |
| lfs_verify multiprocreuse
 | |
| lfs_verify singleprocreuse
 | |
| 
 | |
| echo "--- Results ---"
 | |
| tests/stats.py
 |