git/pack-bitmap-write.c
Neeraj Singh 020406eaa5 core.fsync: introduce granular fsync control infrastructure
This commit introduces the infrastructure for the core.fsync
configuration knob. The repository components we want to sync
are identified by flags so that we can turn on or off syncing
for specific components.

If core.fsyncObjectFiles is set and the core.fsync configuration
also includes FSYNC_COMPONENT_LOOSE_OBJECT, we will fsync any
loose objects. This picks the strictest data integrity behavior
if core.fsync and core.fsyncObjectFiles are set to conflicting values.

This change introduces the currently unused fsync_component
helper, which will be used by a later patch that adds fsyncing to
the refs backend.

Actual configuration and documentation of the fsync components
list are in other patches in the series to separate review of
the underlying mechanism from the policy of how it's configured.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-03-10 15:10:22 -08:00

733 lines
17 KiB
C

#include "cache.h"
#include "object-store.h"
#include "commit.h"
#include "tag.h"
#include "diff.h"
#include "revision.h"
#include "list-objects.h"
#include "progress.h"
#include "pack-revindex.h"
#include "pack.h"
#include "pack-bitmap.h"
#include "hash-lookup.h"
#include "pack-objects.h"
#include "commit-reach.h"
#include "prio-queue.h"
struct bitmapped_commit {
struct commit *commit;
struct ewah_bitmap *bitmap;
struct ewah_bitmap *write_as;
int flags;
int xor_offset;
uint32_t commit_pos;
};
struct bitmap_writer {
struct ewah_bitmap *commits;
struct ewah_bitmap *trees;
struct ewah_bitmap *blobs;
struct ewah_bitmap *tags;
kh_oid_map_t *bitmaps;
struct packing_data *to_pack;
struct bitmapped_commit *selected;
unsigned int selected_nr, selected_alloc;
struct progress *progress;
int show_progress;
unsigned char pack_checksum[GIT_MAX_RAWSZ];
};
static struct bitmap_writer writer;
void bitmap_writer_show_progress(int show)
{
writer.show_progress = show;
}
/**
* Build the initial type index for the packfile or multi-pack-index
*/
void bitmap_writer_build_type_index(struct packing_data *to_pack,
struct pack_idx_entry **index,
uint32_t index_nr)
{
uint32_t i;
writer.commits = ewah_new();
writer.trees = ewah_new();
writer.blobs = ewah_new();
writer.tags = ewah_new();
ALLOC_ARRAY(to_pack->in_pack_pos, to_pack->nr_objects);
for (i = 0; i < index_nr; ++i) {
struct object_entry *entry = (struct object_entry *)index[i];
enum object_type real_type;
oe_set_in_pack_pos(to_pack, entry, i);
switch (oe_type(entry)) {
case OBJ_COMMIT:
case OBJ_TREE:
case OBJ_BLOB:
case OBJ_TAG:
real_type = oe_type(entry);
break;
default:
real_type = oid_object_info(to_pack->repo,
&entry->idx.oid, NULL);
break;
}
switch (real_type) {
case OBJ_COMMIT:
ewah_set(writer.commits, i);
break;
case OBJ_TREE:
ewah_set(writer.trees, i);
break;
case OBJ_BLOB:
ewah_set(writer.blobs, i);
break;
case OBJ_TAG:
ewah_set(writer.tags, i);
break;
default:
die("Missing type information for %s (%d/%d)",
oid_to_hex(&entry->idx.oid), real_type,
oe_type(entry));
}
}
}
/**
* Compute the actual bitmaps
*/
static inline void push_bitmapped_commit(struct commit *commit)
{
if (writer.selected_nr >= writer.selected_alloc) {
writer.selected_alloc = (writer.selected_alloc + 32) * 2;
REALLOC_ARRAY(writer.selected, writer.selected_alloc);
}
writer.selected[writer.selected_nr].commit = commit;
writer.selected[writer.selected_nr].bitmap = NULL;
writer.selected[writer.selected_nr].flags = 0;
writer.selected_nr++;
}
static uint32_t find_object_pos(const struct object_id *oid, int *found)
{
struct object_entry *entry = packlist_find(writer.to_pack, oid);
if (!entry) {
if (found)
*found = 0;
warning("Failed to write bitmap index. Packfile doesn't have full closure "
"(object %s is missing)", oid_to_hex(oid));
return 0;
}
if (found)
*found = 1;
return oe_in_pack_pos(writer.to_pack, entry);
}
static void compute_xor_offsets(void)
{
static const int MAX_XOR_OFFSET_SEARCH = 10;
int i, next = 0;
while (next < writer.selected_nr) {
struct bitmapped_commit *stored = &writer.selected[next];
int best_offset = 0;
struct ewah_bitmap *best_bitmap = stored->bitmap;
struct ewah_bitmap *test_xor;
for (i = 1; i <= MAX_XOR_OFFSET_SEARCH; ++i) {
int curr = next - i;
if (curr < 0)
break;
test_xor = ewah_pool_new();
ewah_xor(writer.selected[curr].bitmap, stored->bitmap, test_xor);
if (test_xor->buffer_size < best_bitmap->buffer_size) {
if (best_bitmap != stored->bitmap)
ewah_pool_free(best_bitmap);
best_bitmap = test_xor;
best_offset = i;
} else {
ewah_pool_free(test_xor);
}
}
stored->xor_offset = best_offset;
stored->write_as = best_bitmap;
next++;
}
}
struct bb_commit {
struct commit_list *reverse_edges;
struct bitmap *commit_mask;
struct bitmap *bitmap;
unsigned selected:1,
maximal:1;
unsigned idx; /* within selected array */
};
define_commit_slab(bb_data, struct bb_commit);
struct bitmap_builder {
struct bb_data data;
struct commit **commits;
size_t commits_nr, commits_alloc;
};
static void bitmap_builder_init(struct bitmap_builder *bb,
struct bitmap_writer *writer,
struct bitmap_index *old_bitmap)
{
struct rev_info revs;
struct commit *commit;
struct commit_list *reusable = NULL;
struct commit_list *r;
unsigned int i, num_maximal = 0;
memset(bb, 0, sizeof(*bb));
init_bb_data(&bb->data);
reset_revision_walk();
repo_init_revisions(writer->to_pack->repo, &revs, NULL);
revs.topo_order = 1;
revs.first_parent_only = 1;
for (i = 0; i < writer->selected_nr; i++) {
struct commit *c = writer->selected[i].commit;
struct bb_commit *ent = bb_data_at(&bb->data, c);
ent->selected = 1;
ent->maximal = 1;
ent->idx = i;
ent->commit_mask = bitmap_new();
bitmap_set(ent->commit_mask, i);
add_pending_object(&revs, &c->object, "");
}
if (prepare_revision_walk(&revs))
die("revision walk setup failed");
while ((commit = get_revision(&revs))) {
struct commit_list *p = commit->parents;
struct bb_commit *c_ent;
parse_commit_or_die(commit);
c_ent = bb_data_at(&bb->data, commit);
/*
* If there is no commit_mask, there is no reason to iterate
* over this commit; it is not selected (if it were, it would
* not have a blank commit mask) and all its children have
* existing bitmaps (see the comment starting with "This commit
* has an existing bitmap" below), so it does not contribute
* anything to the final bitmap file or its descendants.
*/
if (!c_ent->commit_mask)
continue;
if (old_bitmap && bitmap_for_commit(old_bitmap, commit)) {
/*
* This commit has an existing bitmap, so we can
* get its bits immediately without an object
* walk. That is, it is reusable as-is and there is no
* need to continue walking beyond it.
*
* Mark it as such and add it to bb->commits separately
* to avoid allocating a position in the commit mask.
*/
commit_list_insert(commit, &reusable);
goto next;
}
if (c_ent->maximal) {
num_maximal++;
ALLOC_GROW(bb->commits, bb->commits_nr + 1, bb->commits_alloc);
bb->commits[bb->commits_nr++] = commit;
}
if (p) {
struct bb_commit *p_ent = bb_data_at(&bb->data, p->item);
int c_not_p, p_not_c;
if (!p_ent->commit_mask) {
p_ent->commit_mask = bitmap_new();
c_not_p = 1;
p_not_c = 0;
} else {
c_not_p = bitmap_is_subset(c_ent->commit_mask, p_ent->commit_mask);
p_not_c = bitmap_is_subset(p_ent->commit_mask, c_ent->commit_mask);
}
if (!c_not_p)
continue;
bitmap_or(p_ent->commit_mask, c_ent->commit_mask);
if (p_not_c)
p_ent->maximal = 1;
else {
p_ent->maximal = 0;
free_commit_list(p_ent->reverse_edges);
p_ent->reverse_edges = NULL;
}
if (c_ent->maximal) {
commit_list_insert(commit, &p_ent->reverse_edges);
} else {
struct commit_list *cc = c_ent->reverse_edges;
for (; cc; cc = cc->next) {
if (!commit_list_contains(cc->item, p_ent->reverse_edges))
commit_list_insert(cc->item, &p_ent->reverse_edges);
}
}
}
next:
bitmap_free(c_ent->commit_mask);
c_ent->commit_mask = NULL;
}
for (r = reusable; r; r = r->next) {
ALLOC_GROW(bb->commits, bb->commits_nr + 1, bb->commits_alloc);
bb->commits[bb->commits_nr++] = r->item;
}
trace2_data_intmax("pack-bitmap-write", the_repository,
"num_selected_commits", writer->selected_nr);
trace2_data_intmax("pack-bitmap-write", the_repository,
"num_maximal_commits", num_maximal);
free_commit_list(reusable);
}
static void bitmap_builder_clear(struct bitmap_builder *bb)
{
clear_bb_data(&bb->data);
free(bb->commits);
bb->commits_nr = bb->commits_alloc = 0;
}
static int fill_bitmap_tree(struct bitmap *bitmap,
struct tree *tree)
{
int found;
uint32_t pos;
struct tree_desc desc;
struct name_entry entry;
/*
* If our bit is already set, then there is nothing to do. Both this
* tree and all of its children will be set.
*/
pos = find_object_pos(&tree->object.oid, &found);
if (!found)
return -1;
if (bitmap_get(bitmap, pos))
return 0;
bitmap_set(bitmap, pos);
if (parse_tree(tree) < 0)
die("unable to load tree object %s",
oid_to_hex(&tree->object.oid));
init_tree_desc(&desc, tree->buffer, tree->size);
while (tree_entry(&desc, &entry)) {
switch (object_type(entry.mode)) {
case OBJ_TREE:
if (fill_bitmap_tree(bitmap,
lookup_tree(the_repository, &entry.oid)) < 0)
return -1;
break;
case OBJ_BLOB:
pos = find_object_pos(&entry.oid, &found);
if (!found)
return -1;
bitmap_set(bitmap, pos);
break;
default:
/* Gitlink, etc; not reachable */
break;
}
}
free_tree_buffer(tree);
return 0;
}
static int fill_bitmap_commit(struct bb_commit *ent,
struct commit *commit,
struct prio_queue *queue,
struct prio_queue *tree_queue,
struct bitmap_index *old_bitmap,
const uint32_t *mapping)
{
int found;
uint32_t pos;
if (!ent->bitmap)
ent->bitmap = bitmap_new();
prio_queue_put(queue, commit);
while (queue->nr) {
struct commit_list *p;
struct commit *c = prio_queue_get(queue);
if (old_bitmap && mapping) {
struct ewah_bitmap *old = bitmap_for_commit(old_bitmap, c);
/*
* If this commit has an old bitmap, then translate that
* bitmap and add its bits to this one. No need to walk
* parents or the tree for this commit.
*/
if (old && !rebuild_bitmap(mapping, old, ent->bitmap))
continue;
}
/*
* Mark ourselves and queue our tree. The commit
* walk ensures we cover all parents.
*/
pos = find_object_pos(&c->object.oid, &found);
if (!found)
return -1;
bitmap_set(ent->bitmap, pos);
prio_queue_put(tree_queue, get_commit_tree(c));
for (p = c->parents; p; p = p->next) {
pos = find_object_pos(&p->item->object.oid, &found);
if (!found)
return -1;
if (!bitmap_get(ent->bitmap, pos)) {
bitmap_set(ent->bitmap, pos);
prio_queue_put(queue, p->item);
}
}
}
while (tree_queue->nr) {
if (fill_bitmap_tree(ent->bitmap,
prio_queue_get(tree_queue)) < 0)
return -1;
}
return 0;
}
static void store_selected(struct bb_commit *ent, struct commit *commit)
{
struct bitmapped_commit *stored = &writer.selected[ent->idx];
khiter_t hash_pos;
int hash_ret;
stored->bitmap = bitmap_to_ewah(ent->bitmap);
hash_pos = kh_put_oid_map(writer.bitmaps, commit->object.oid, &hash_ret);
if (hash_ret == 0)
die("Duplicate entry when writing index: %s",
oid_to_hex(&commit->object.oid));
kh_value(writer.bitmaps, hash_pos) = stored;
}
int bitmap_writer_build(struct packing_data *to_pack)
{
struct bitmap_builder bb;
size_t i;
int nr_stored = 0; /* for progress */
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
struct prio_queue tree_queue = { NULL };
struct bitmap_index *old_bitmap;
uint32_t *mapping;
int closed = 1; /* until proven otherwise */
writer.bitmaps = kh_init_oid_map();
writer.to_pack = to_pack;
if (writer.show_progress)
writer.progress = start_progress("Building bitmaps", writer.selected_nr);
trace2_region_enter("pack-bitmap-write", "building_bitmaps_total",
the_repository);
old_bitmap = prepare_bitmap_git(to_pack->repo);
if (old_bitmap)
mapping = create_bitmap_mapping(old_bitmap, to_pack);
else
mapping = NULL;
bitmap_builder_init(&bb, &writer, old_bitmap);
for (i = bb.commits_nr; i > 0; i--) {
struct commit *commit = bb.commits[i-1];
struct bb_commit *ent = bb_data_at(&bb.data, commit);
struct commit *child;
int reused = 0;
if (fill_bitmap_commit(ent, commit, &queue, &tree_queue,
old_bitmap, mapping) < 0) {
closed = 0;
break;
}
if (ent->selected) {
store_selected(ent, commit);
nr_stored++;
display_progress(writer.progress, nr_stored);
}
while ((child = pop_commit(&ent->reverse_edges))) {
struct bb_commit *child_ent =
bb_data_at(&bb.data, child);
if (child_ent->bitmap)
bitmap_or(child_ent->bitmap, ent->bitmap);
else if (reused)
child_ent->bitmap = bitmap_dup(ent->bitmap);
else {
child_ent->bitmap = ent->bitmap;
reused = 1;
}
}
if (!reused)
bitmap_free(ent->bitmap);
ent->bitmap = NULL;
}
clear_prio_queue(&queue);
clear_prio_queue(&tree_queue);
bitmap_builder_clear(&bb);
free_bitmap_index(old_bitmap);
free(mapping);
trace2_region_leave("pack-bitmap-write", "building_bitmaps_total",
the_repository);
stop_progress(&writer.progress);
if (closed)
compute_xor_offsets();
return closed ? 0 : -1;
}
/**
* Select the commits that will be bitmapped
*/
static inline unsigned int next_commit_index(unsigned int idx)
{
static const unsigned int MIN_COMMITS = 100;
static const unsigned int MAX_COMMITS = 5000;
static const unsigned int MUST_REGION = 100;
static const unsigned int MIN_REGION = 20000;
unsigned int offset, next;
if (idx <= MUST_REGION)
return 0;
if (idx <= MIN_REGION) {
offset = idx - MUST_REGION;
return (offset < MIN_COMMITS) ? offset : MIN_COMMITS;
}
offset = idx - MIN_REGION;
next = (offset < MAX_COMMITS) ? offset : MAX_COMMITS;
return (next > MIN_COMMITS) ? next : MIN_COMMITS;
}
static int date_compare(const void *_a, const void *_b)
{
struct commit *a = *(struct commit **)_a;
struct commit *b = *(struct commit **)_b;
return (long)b->date - (long)a->date;
}
void bitmap_writer_select_commits(struct commit **indexed_commits,
unsigned int indexed_commits_nr,
int max_bitmaps)
{
unsigned int i = 0, j, next;
QSORT(indexed_commits, indexed_commits_nr, date_compare);
if (indexed_commits_nr < 100) {
for (i = 0; i < indexed_commits_nr; ++i)
push_bitmapped_commit(indexed_commits[i]);
return;
}
if (writer.show_progress)
writer.progress = start_progress("Selecting bitmap commits", 0);
for (;;) {
struct commit *chosen = NULL;
next = next_commit_index(i);
if (i + next >= indexed_commits_nr)
break;
if (max_bitmaps > 0 && writer.selected_nr >= max_bitmaps) {
writer.selected_nr = max_bitmaps;
break;
}
if (next == 0) {
chosen = indexed_commits[i];
} else {
chosen = indexed_commits[i + next];
for (j = 0; j <= next; ++j) {
struct commit *cm = indexed_commits[i + j];
if ((cm->object.flags & NEEDS_BITMAP) != 0) {
chosen = cm;
break;
}
if (cm->parents && cm->parents->next)
chosen = cm;
}
}
push_bitmapped_commit(chosen);
i += next + 1;
display_progress(writer.progress, i);
}
stop_progress(&writer.progress);
}
static int hashwrite_ewah_helper(void *f, const void *buf, size_t len)
{
/* hashwrite will die on error */
hashwrite(f, buf, len);
return len;
}
/**
* Write the bitmap index to disk
*/
static inline void dump_bitmap(struct hashfile *f, struct ewah_bitmap *bitmap)
{
if (ewah_serialize_to(bitmap, hashwrite_ewah_helper, f) < 0)
die("Failed to write bitmap index");
}
static const struct object_id *oid_access(size_t pos, const void *table)
{
const struct pack_idx_entry * const *index = table;
return &index[pos]->oid;
}
static void write_selected_commits_v1(struct hashfile *f,
struct pack_idx_entry **index,
uint32_t index_nr)
{
int i;
for (i = 0; i < writer.selected_nr; ++i) {
struct bitmapped_commit *stored = &writer.selected[i];
int commit_pos =
oid_pos(&stored->commit->object.oid, index, index_nr, oid_access);
if (commit_pos < 0)
BUG("trying to write commit not in index");
hashwrite_be32(f, commit_pos);
hashwrite_u8(f, stored->xor_offset);
hashwrite_u8(f, stored->flags);
dump_bitmap(f, stored->write_as);
}
}
static void write_hash_cache(struct hashfile *f,
struct pack_idx_entry **index,
uint32_t index_nr)
{
uint32_t i;
for (i = 0; i < index_nr; ++i) {
struct object_entry *entry = (struct object_entry *)index[i];
hashwrite_be32(f, entry->hash);
}
}
void bitmap_writer_set_checksum(unsigned char *sha1)
{
hashcpy(writer.pack_checksum, sha1);
}
void bitmap_writer_finish(struct pack_idx_entry **index,
uint32_t index_nr,
const char *filename,
uint16_t options)
{
static uint16_t default_version = 1;
static uint16_t flags = BITMAP_OPT_FULL_DAG;
struct strbuf tmp_file = STRBUF_INIT;
struct hashfile *f;
struct bitmap_disk_header header;
int fd = odb_mkstemp(&tmp_file, "pack/tmp_bitmap_XXXXXX");
f = hashfd(fd, tmp_file.buf);
memcpy(header.magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE));
header.version = htons(default_version);
header.options = htons(flags | options);
header.entry_count = htonl(writer.selected_nr);
hashcpy(header.checksum, writer.pack_checksum);
hashwrite(f, &header, sizeof(header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz);
dump_bitmap(f, writer.commits);
dump_bitmap(f, writer.trees);
dump_bitmap(f, writer.blobs);
dump_bitmap(f, writer.tags);
write_selected_commits_v1(f, index, index_nr);
if (options & BITMAP_OPT_HASH_CACHE)
write_hash_cache(f, index, index_nr);
finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK_METADATA,
CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
if (adjust_shared_perm(tmp_file.buf))
die_errno("unable to make temporary bitmap file readable");
if (rename(tmp_file.buf, filename))
die_errno("unable to rename temporary bitmap file to '%s'", filename);
strbuf_release(&tmp_file);
}