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Document communication between metadata server and clients in the misc/PROTOCOL.txt file and add generation counters for files

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cozis
2025-11-24 13:04:29 +01:00
parent 1c768bb8f1
commit 49091aff6d
7 changed files with 445 additions and 98 deletions
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src/file_tree.c
+75 -26
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@@ -3,6 +3,7 @@
#include <string.h>
#include <stdlib.h>
#include "basic.h"
#include "system.h"
#include "file_tree.h"
@@ -104,10 +105,32 @@ static void dir_free(Dir *d)
sys_free(d->children);
}
static void dir_remove(Dir *d, int idx)
static bool gen_match(uint64_t expected_gen, uint64_t entity_gen)
{
assert(entity_gen != NO_GENERATION);
if (expected_gen == NO_GENERATION)
return true;
return expected_gen == entity_gen;
}
static uint64_t create_generation(uint64_t *next_gen)
{
(*next_gen)++;
if (*next_gen == 0 || *next_gen == UINT64_MAX)
*next_gen = 1;
return *next_gen;
}
static int dir_remove(Dir *d, int idx, uint64_t expected_gen)
{
if (!gen_match(expected_gen, d->children[idx].gen))
return -1;
// TODO: pretty sure this leaks memory
d->children[idx] = d->children[--d->num_children];
return 0;
}
static bool dir_uses_hash(Dir *d, SHA256 hash)
@@ -142,10 +165,14 @@ static bool file_uses_hash(File *f, SHA256 hash)
// Fails when the name is too long
static int entity_init(Entity *e, char *name, int name_len,
bool is_dir, uint64_t chunk_size)
bool is_dir, uint64_t chunk_size, uint64_t *next_gen)
{
if (name_len >= (int) sizeof(e->name))
return -1;
e->gen = create_generation(next_gen);
assert(e->gen != NO_GENERATION);
memcpy(e->name, name, name_len);
e->name[name_len] = '\0';
e->name_len = (uint16_t) name_len;
@@ -177,7 +204,9 @@ static bool entity_uses_hash(Entity *e, SHA256 hash)
int file_tree_init(FileTree *ft)
{
int ret = entity_init(&ft->root, "", 0, true, 0);
ft->next_gen = 1;
int ret = entity_init(&ft->root, "", 0, true, 0, &ft->next_gen);
if (ret < 0) return -1;
return 0;
@@ -194,7 +223,7 @@ bool file_tree_uses_hash(FileTree *ft, SHA256 hash)
}
int file_tree_list(FileTree *ft, string path,
ListItem *items, int max_items)
ListItem *items, int max_items, uint64_t *gen)
{
int num_comps;
string comps[MAX_COMPS];
@@ -230,11 +259,14 @@ int file_tree_list(FileTree *ft, string path,
items[i].is_dir = c->is_dir;
}
assert(e->gen != NO_GENERATION);
*gen = e->gen;
return d->num_children;
}
int file_tree_create_entity(FileTree *ft, string path,
bool is_dir, uint64_t chunk_size)
bool is_dir, uint64_t chunk_size, uint64_t *gen)
{
int num_comps;
string comps[MAX_COMPS];
@@ -285,17 +317,21 @@ int file_tree_create_entity(FileTree *ft, string path,
}
Entity *c = &d->children[d->num_children];
int ret = entity_init(c, (char*) name.ptr, name.len, is_dir, chunk_size);
int ret = entity_init(c, (char*) name.ptr, name.len, is_dir, chunk_size, &ft->next_gen);
if (ret < 0)
// Invalid name for the new file
return FILETREE_BADPATH;
assert(e->gen != NO_GENERATION);
*gen = e->gen;
d->num_children++;
return 0;
}
// TODO: this should return the list of unreferenced hashes
int file_tree_delete_entity(FileTree *ft, string path)
int file_tree_delete_entity(FileTree *ft, string path,
uint64_t expected_gen)
{
int num_comps;
string comps[MAX_COMPS];
@@ -316,14 +352,18 @@ int file_tree_delete_entity(FileTree *ft, string path)
if (i == -1)
return FILETREE_NOENT;
dir_remove(&e->d, i);
if (dir_remove(&e->d, i, expected_gen) < 0)
return -1; // TODO: proper error code
return 0;
}
int file_tree_write(FileTree *ft, string path,
uint64_t off, uint64_t len, uint32_t num_chunks,
uint32_t chunk_size, SHA256 *prev_hashes,
SHA256 *hashes, SHA256 *removed_hashes,
uint64_t expect_gen,
uint64_t *new_gen,
SHA256 *hashes,
SHA256 *removed_hashes,
int *num_removed)
{
int num_comps;
@@ -341,10 +381,10 @@ int file_tree_write(FileTree *ft, string path,
if (e->is_dir)
return FILETREE_ISDIR;
File *f = &e->f;
if (!gen_match(expect_gen, e->gen))
return -1; // TODO: proper error code
if (f->chunk_size != chunk_size)
return -1; // TODO: error code
File *f = &e->f;
uint64_t first_chunk_index = off / f->chunk_size;
uint64_t last_chunk_index = first_chunk_index + (len - 1) / f->chunk_size;
@@ -367,14 +407,17 @@ int file_tree_write(FileTree *ft, string path,
memset(&f->chunks[i], 0, sizeof(SHA256));
}
// Verify prev_hashes match
for (uint64_t i = first_chunk_index; i <= last_chunk_index; i++)
if (memcmp(&f->chunks[i], &prev_hashes[i - first_chunk_index], sizeof(SHA256)))
return -1; // TODO: error code
int num_overwritten_hashes = 0;
SHA256 overwritten_hashes[100]; // TODO: fix this limit
if (num_chunks > 100) {
assert(0); // TODO
}
// Update chunks
for (uint64_t i = first_chunk_index; i <= last_chunk_index; i++)
for (uint64_t i = first_chunk_index; i <= last_chunk_index; i++) {
overwritten_hashes[num_overwritten_hashes++] = f->chunks[i];
f->chunks[i] = hashes[i - first_chunk_index];
}
// Update file size (last byte written + 1)
uint64_t new_size = off + len;
@@ -388,13 +431,14 @@ int file_tree_write(FileTree *ft, string path,
// interested in which hashes are no longer reachable.
if (removed_hashes != NULL) {
*num_removed = 0;
for (uint64_t i = first_chunk_index; i <= last_chunk_index; i++) {
SHA256 old_hash = prev_hashes[i - first_chunk_index];
for (int i = 0; i < num_overwritten_hashes; i++) {
SHA256 hash = overwritten_hashes[i];
// Skip zero hashes
bool is_zero = true;
for (int j = 0; j < (int) sizeof(SHA256); j++) {
if (old_hash.data[j] != 0) {
if (hash.data[j] != 0) {
is_zero = false;
break;
}
@@ -403,20 +447,22 @@ int file_tree_write(FileTree *ft, string path,
continue;
// Check if this hash is still used anywhere in the tree
if (!entity_uses_hash(&ft->root, old_hash)) {
// Not used - add to removed list
if (removed_hashes)
removed_hashes[*num_removed] = old_hash;
if (!entity_uses_hash(&ft->root, hash)) {
removed_hashes[*num_removed] = hash;
(*num_removed)++;
}
}
}
e->gen = create_generation(&ft->next_gen);
assert(e->gen != NO_GENERATION);
*new_gen = e->gen;
return 0;
}
int file_tree_read(FileTree *ft, string path,
uint64_t off, uint64_t len, uint64_t *chunk_size,
uint64_t off, uint64_t len, uint64_t *gen, uint64_t *chunk_size,
SHA256 *hashes, int max_hashes, uint64_t *actual_bytes)
{
int num_comps;
@@ -472,6 +518,9 @@ int file_tree_read(FileTree *ft, string path,
num_hashes++;
}
assert(e->gen != NO_GENERATION);
*gen = e->gen;
return num_hashes;
}