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stage1 caching system: detect problematic mtimes

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closes #2045
This commit is contained in:
Andrew Kelley
2019-03-11 10:26:08 -04:00
parent fec4555476
commit 3a6f19de48
8 changed files with 189 additions and 70 deletions
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97
src/cache_hash.cpp
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@@ -158,8 +158,10 @@ static void base64_encode(Slice<uint8_t> dest, Slice<uint8_t> source) {
// Ported from std/base64.zig
static Error base64_decode(Slice<uint8_t> dest, Slice<uint8_t> source) {
assert(source.len % 4 == 0);
assert(dest.len == (source.len / 4) * 3);
if (source.len % 4 != 0)
return ErrorInvalidFormat;
if (dest.len != (source.len / 4) * 3)
return ErrorInvalidFormat;
// In Zig this is comptime computed. In C++ it's not worth it to do that.
uint8_t char_to_index[256];
@@ -218,15 +220,41 @@ static Error hash_file(uint8_t *digest, OsFile handle, Buf *contents) {
}
}
// If the wall clock time, rounded to the same precision as the
// mtime, is equal to the mtime, then we cannot rely on this mtime
// yet. We will instead save an mtime value that indicates the hash
// must be unconditionally computed.
static bool is_problematic_timestamp(const OsTimeStamp *fs_clock) {
OsTimeStamp wall_clock = os_timestamp_calendar();
// First make all the least significant zero bits in the fs_clock, also zero bits in the wall clock.
if (fs_clock->nsec == 0) {
wall_clock.nsec = 0;
if (fs_clock->sec == 0) {
wall_clock.sec = 0;
} else {
wall_clock.sec &= (-1ull) << ctzll(fs_clock->sec);
}
} else {
wall_clock.nsec &= (-1ull) << ctzll(fs_clock->nsec);
}
return wall_clock.nsec == fs_clock->nsec && wall_clock.sec == fs_clock->sec;
}
static Error populate_file_hash(CacheHash *ch, CacheHashFile *chf, Buf *contents) {
Error err;
assert(chf->path != nullptr);
OsFile this_file;
if ((err = os_file_open_r(chf->path, &this_file, &chf->mtime)))
if ((err = os_file_open_r(chf->path, &this_file, &chf->attr)))
return err;
if (is_problematic_timestamp(&chf->attr.mtime)) {
chf->attr.mtime.sec = 0;
chf->attr.mtime.nsec = 0;
chf->attr.inode = 0;
}
if ((err = hash_file(chf->bin_digest, this_file, contents))) {
os_file_close(this_file);
return err;
@@ -278,6 +306,7 @@ Error cache_hit(CacheHash *ch, Buf *out_digest) {
size_t input_file_count = ch->files.length;
bool any_file_changed = false;
Error return_code = ErrorNone;
size_t file_i = 0;
SplitIterator line_it = memSplit(buf_to_slice(&line_buf), str("\n"));
for (;; file_i += 1) {
@@ -299,7 +328,7 @@ Error cache_hit(CacheHash *ch, Buf *out_digest) {
blake2b_update(&ch->blake, ch->files.at(file_i).bin_digest, 48);
}
// caller can notice that out_digest is unmodified.
return ErrorNone;
return return_code;
} else if (!opt_line.is_some) {
break;
} else {
@@ -312,57 +341,73 @@ Error cache_hit(CacheHash *ch, Buf *out_digest) {
SplitIterator it = memSplit(opt_line.value, str(" "));
Optional<Slice<uint8_t>> opt_inode = SplitIterator_next(&it);
if (!opt_inode.is_some) {
return_code = ErrorInvalidFormat;
break;
}
chf->attr.inode = strtoull((const char *)opt_inode.value.ptr, nullptr, 10);
Optional<Slice<uint8_t>> opt_mtime_sec = SplitIterator_next(&it);
if (!opt_mtime_sec.is_some) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
chf->mtime.sec = strtoull((const char *)opt_mtime_sec.value.ptr, nullptr, 10);
chf->attr.mtime.sec = strtoull((const char *)opt_mtime_sec.value.ptr, nullptr, 10);
Optional<Slice<uint8_t>> opt_mtime_nsec = SplitIterator_next(&it);
if (!opt_mtime_nsec.is_some) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
chf->mtime.nsec = strtoull((const char *)opt_mtime_nsec.value.ptr, nullptr, 10);
chf->attr.mtime.nsec = strtoull((const char *)opt_mtime_nsec.value.ptr, nullptr, 10);
Optional<Slice<uint8_t>> opt_digest = SplitIterator_next(&it);
if (!opt_digest.is_some) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
if ((err = base64_decode({chf->bin_digest, 48}, opt_digest.value))) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
Slice<uint8_t> file_path = SplitIterator_rest(&it);
if (file_path.len == 0) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
Buf *this_path = buf_create_from_slice(file_path);
if (chf->path != nullptr && !buf_eql_buf(this_path, chf->path)) {
os_file_close(ch->manifest_file);
return ErrorInvalidFormat;
return_code = ErrorInvalidFormat;
break;
}
chf->path = this_path;
// if the mtime matches we can trust the digest
OsFile this_file;
OsTimeStamp actual_mtime;
if ((err = os_file_open_r(chf->path, &this_file, &actual_mtime))) {
OsFileAttr actual_attr;
if ((err = os_file_open_r(chf->path, &this_file, &actual_attr))) {
fprintf(stderr, "Unable to open %s\n: %s", buf_ptr(chf->path), err_str(err));
os_file_close(ch->manifest_file);
return ErrorCacheUnavailable;
}
if (chf->mtime.sec == actual_mtime.sec && chf->mtime.nsec == actual_mtime.nsec) {
if (chf->attr.mtime.sec == actual_attr.mtime.sec &&
chf->attr.mtime.nsec == actual_attr.mtime.nsec &&
chf->attr.inode == actual_attr.inode)
{
os_file_close(this_file);
} else {
// we have to recompute the digest.
// later we'll rewrite the manifest with the new mtime/digest values
ch->manifest_dirty = true;
chf->mtime = actual_mtime;
chf->attr = actual_attr;
if (is_problematic_timestamp(&actual_attr.mtime)) {
chf->attr.mtime.sec = 0;
chf->attr.mtime.nsec = 0;
chf->attr.inode = 0;
}
uint8_t actual_digest[48];
if ((err = hash_file(actual_digest, this_file, nullptr))) {
@@ -381,7 +426,7 @@ Error cache_hit(CacheHash *ch, Buf *out_digest) {
blake2b_update(&ch->blake, chf->bin_digest, 48);
}
}
if (file_i < input_file_count || file_i == 0) {
if (file_i < input_file_count || file_i == 0 || return_code != ErrorNone) {
// manifest file is empty or missing entries, so this is a cache miss
ch->manifest_dirty = true;
for (; file_i < input_file_count; file_i += 1) {
@@ -392,7 +437,7 @@ Error cache_hit(CacheHash *ch, Buf *out_digest) {
return ErrorCacheUnavailable;
}
}
return ErrorNone;
return return_code;
}
// Cache Hit
return cache_final(ch, out_digest);
@@ -499,8 +544,8 @@ static Error write_manifest_file(CacheHash *ch) {
for (size_t i = 0; i < ch->files.length; i += 1) {
CacheHashFile *chf = &ch->files.at(i);
base64_encode({encoded_digest, 64}, {chf->bin_digest, 48});
buf_appendf(&contents, "%" ZIG_PRI_u64 " %" ZIG_PRI_u64 " %s %s\n",
chf->mtime.sec, chf->mtime.nsec, encoded_digest, buf_ptr(chf->path));
buf_appendf(&contents, "%" ZIG_PRI_u64 " %" ZIG_PRI_u64 " %" ZIG_PRI_u64 " %s %s\n",
chf->attr.inode, chf->attr.mtime.sec, chf->attr.mtime.nsec, encoded_digest, buf_ptr(chf->path));
}
if ((err = os_file_overwrite(ch->manifest_file, &contents)))
return err;