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Merge branch 'jt/v2-fetch-nego-fix'
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The upload-pack protocol v2 gave up too early before finding a
common ancestor, resulting in a wasteful fetch from a fork of a
project.  This has been corrected to match the behaviour of v0
protocol.

* jt/v2-fetch-nego-fix:
  fetch-pack: in protocol v2, reset in_vain upon ACK
  fetch-pack: in protocol v2, in_vain only after ACK
  fetch-pack: return enum from process_acks()
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@gitster
gitster committed May 1, 2020
2 parents 2c42fb7 + 2f0a093 commit 0b07eec
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Showing 2 changed files with 86 additions and 12 deletions.
50 changes: 38 additions & 12 deletions fetch-pack.c
View file
Expand Up @@ -1143,6 +1143,7 @@ static void add_common(struct strbuf *req_buf, struct oidset *common)
}

static int add_haves(struct fetch_negotiator *negotiator,
int seen_ack,
struct strbuf *req_buf,
int *haves_to_send, int *in_vain)
{
Expand All @@ -1157,7 +1158,7 @@ static int add_haves(struct fetch_negotiator *negotiator,
}

*in_vain += haves_added;
if (!haves_added || *in_vain >= MAX_IN_VAIN) {
if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
/* Send Done */
packet_buf_write(req_buf, "done\n");
ret = 1;
Expand All @@ -1173,7 +1174,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
struct fetch_pack_args *args,
const struct ref *wants, struct oidset *common,
int *haves_to_send, int *in_vain,
int sideband_all)
int sideband_all, int seen_ack)
{
int ret = 0;
struct strbuf req_buf = STRBUF_INIT;
Expand Down Expand Up @@ -1230,7 +1231,8 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
add_common(&req_buf, common);

/* Add initial haves */
ret = add_haves(negotiator, &req_buf, haves_to_send, in_vain);
ret = add_haves(negotiator, seen_ack, &req_buf,
haves_to_send, in_vain);
}

/* Send request */
Expand Down Expand Up @@ -1268,9 +1270,29 @@ static int process_section_header(struct packet_reader *reader,
return ret;
}

static int process_acks(struct fetch_negotiator *negotiator,
struct packet_reader *reader,
struct oidset *common)
enum common_found {
/*
* No commit was found to be possessed by both the client and the
* server, and "ready" was not received.
*/
NO_COMMON_FOUND,

/*
* At least one commit was found to be possessed by both the client and
* the server, and "ready" was not received.
*/
COMMON_FOUND,

/*
* "ready" was received, indicating that the server is ready to send
* the packfile without any further negotiation.
*/
READY
};

static enum common_found process_acks(struct fetch_negotiator *negotiator,
struct packet_reader *reader,
struct oidset *common)
{
/* received */
int received_ready = 0;
Expand All @@ -1285,6 +1307,7 @@ static int process_acks(struct fetch_negotiator *negotiator,

if (skip_prefix(reader->line, "ACK ", &arg)) {
struct object_id oid;
received_ack = 1;
if (!get_oid_hex(arg, &oid)) {
struct commit *commit;
oidset_insert(common, &oid);
Expand Down Expand Up @@ -1319,8 +1342,8 @@ static int process_acks(struct fetch_negotiator *negotiator,
if (!received_ready && reader->status != PACKET_READ_FLUSH)
die(_("expected no other sections to be sent after no 'ready'"));

/* return 0 if no common, 1 if there are common, or 2 if ready */
return received_ready ? 2 : (received_ack ? 1 : 0);
return received_ready ? READY :
(received_ack ? COMMON_FOUND : NO_COMMON_FOUND);
}

static void receive_shallow_info(struct fetch_pack_args *args,
Expand Down Expand Up @@ -1444,6 +1467,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
int haves_to_send = INITIAL_FLUSH;
struct fetch_negotiator negotiator_alloc;
struct fetch_negotiator *negotiator;
int seen_ack = 0;

if (args->no_dependents) {
negotiator = NULL;
Expand Down Expand Up @@ -1500,21 +1524,23 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
if (send_fetch_request(negotiator, fd[1], args, ref,
&common,
&haves_to_send, &in_vain,
reader.use_sideband))
reader.use_sideband,
seen_ack))
state = FETCH_GET_PACK;
else
state = FETCH_PROCESS_ACKS;
break;
case FETCH_PROCESS_ACKS:
/* Process ACKs/NAKs */
switch (process_acks(negotiator, &reader, &common)) {
case 2:
case READY:
state = FETCH_GET_PACK;
break;
case 1:
case COMMON_FOUND:
in_vain = 0;
seen_ack = 1;
/* fallthrough */
default:
case NO_COMMON_FOUND:
state = FETCH_SEND_REQUEST;
break;
}
Expand Down
48 changes: 48 additions & 0 deletions t/t5500-fetch-pack.sh
View file
Expand Up @@ -385,6 +385,54 @@ test_expect_success 'clone shallow with packed refs' '
test_cmp count8.expected count8.actual
'

test_expect_success 'in_vain not triggered before first ACK' '
rm -rf myserver myclient trace &&
git init myserver &&
test_commit -C myserver foo &&
git clone "file://$(pwd)/myserver" myclient &&
# MAX_IN_VAIN is 256. Because of batching, the client will send 496
# (16+32+64+128+256) commits, not 256, before giving up. So create 496
# irrelevant commits.
test_commit_bulk -C myclient 496 &&
# The new commit that the client wants to fetch.
test_commit -C myserver bar &&
GIT_TRACE_PACKET="$(pwd)/trace" git -C myclient fetch --progress origin &&
test_i18ngrep "Total 3 " trace
'

test_expect_success 'in_vain resetted upon ACK' '
rm -rf myserver myclient trace &&
git init myserver &&
# Linked list of commits on master. The first is common; the rest are
# not.
test_commit -C myserver first_master_commit &&
git clone "file://$(pwd)/myserver" myclient &&
test_commit_bulk -C myclient 255 &&
# Another linked list of commits on anotherbranch with no connection to
# master. The first is common; the rest are not.
git -C myserver checkout --orphan anotherbranch &&
test_commit -C myserver first_anotherbranch_commit &&
git -C myclient fetch origin anotherbranch:refs/heads/anotherbranch &&
git -C myclient checkout anotherbranch &&
test_commit_bulk -C myclient 255 &&
# The new commit that the client wants to fetch.
git -C myserver checkout master &&
test_commit -C myserver to_fetch &&
# The client will send (as "have"s) all 256 commits in anotherbranch
# first. The 256th commit is common between the client and the server,
# and should reset in_vain. This allows negotiation to continue until
# the client reports that first_anotherbranch_commit is common.
GIT_TRACE_PACKET="$(pwd)/trace" git -C myclient fetch --progress origin master &&
test_i18ngrep "Total 3 " trace
'

test_expect_success 'fetch in shallow repo unreachable shallow objects' '
(
git clone --bare --branch B --single-branch "file://$(pwd)/." no-reflog &&
Expand Down

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