Instead of manually creating refs/ hierarchy on disk upon a
creation of a secondary worktree, which is only usable via the
files backend, use the refs API to populate it.
* ps/worktree-refdb-initialization:
builtin/worktree: create refdb via ref backend
worktree: expose interface to look up worktree by name
builtin/worktree: move setup of commondir file earlier
refs/files: skip creation of "refs/{heads,tags}" for worktrees
setup: move creation of "refs/" into the files backend
refs: prepare `refs_init_db()` for initializing worktree refs
Introduce a new extension "refstorage" so that we can mark a
repository that uses a non-default ref backend, like reftable.
* ps/refstorage-extension:
t9500: write "extensions.refstorage" into config
builtin/clone: introduce `--ref-format=` value flag
builtin/init: introduce `--ref-format=` value flag
builtin/rev-parse: introduce `--show-ref-format` flag
t: introduce GIT_TEST_DEFAULT_REF_FORMAT envvar
setup: introduce GIT_DEFAULT_REF_FORMAT envvar
setup: introduce "extensions.refStorage" extension
setup: set repository's formats on init
setup: start tracking ref storage format
refs: refactor logic to look up storage backends
worktree: skip reading HEAD when repairing worktrees
t: introduce DEFAULT_REPO_FORMAT prereq
The files ref backend will create both "refs/heads" and "refs/tags" in
the Git directory. While this logic makes sense for normal repositories,
it does not for worktrees because those refs are "common" refs that
would always be contained in the main repository's ref database.
Introduce a new flag telling the backend that it is expected to create a
per-worktree ref database and skip creation of these dirs in the files
backend when the flag is set. No other backends (currently) need
worktree-specific logic, so this is the only required change to start
creating per-worktree ref databases via `refs_init_db()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The purpose of `refs_init_db()` is to initialize the on-disk files of a
new ref database. The function is quite inflexible right now though, as
callers can neither specify the `struct ref_store` nor can they pass any
flags.
Refactor the interface to accept both of these. This will be required so
that we can start initializing per-worktree ref databases via the ref
backend instead of open-coding the initialization in "worktree.c".
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In order to look up ref storage backends, we're currently using a linked
list of backends, where each backend is expected to set up its `next`
pointer to the next ref storage backend. This is kind of a weird setup
as backends need to be aware of other backends without much of a reason.
Refactor the code so that the array of backends is centrally defined in
"refs.c", where each backend is now identified by an integer constant.
Expose functions to translate from those integer constants to the name
and vice versa, which will be required by subsequent patches.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Enumerating refs in the packed-refs file, while excluding refs that
match certain patterns, has been optimized.
* tb/refs-exclusion-and-packed-refs:
ls-refs.c: avoid enumerating hidden refs where possible
upload-pack.c: avoid enumerating hidden refs where possible
builtin/receive-pack.c: avoid enumerating hidden references
refs.h: implement `hidden_refs_to_excludes()`
refs.h: let `for_each_namespaced_ref()` take excluded patterns
revision.h: store hidden refs in a `strvec`
refs/packed-backend.c: add trace2 counters for jump list
refs/packed-backend.c: implement jump lists to avoid excluded pattern(s)
refs/packed-backend.c: refactor `find_reference_location()`
refs: plumb `exclude_patterns` argument throughout
builtin/for-each-ref.c: add `--exclude` option
ref-filter.c: parameterize match functions over patterns
ref-filter: add `ref_filter_clear()`
ref-filter: clear reachable list pointers after freeing
ref-filter.h: provide `REF_FILTER_INIT`
refs.c: rename `ref_filter`
In subsequent commits, we'll teach `receive-pack` and `upload-pack` to
use the new jump list feature in the packed-refs iterator by ignoring
references which are mentioned via its respective hideRefs lists.
However, the packed-ref jump lists cannot handle un-hiding rules (that
begin with '!'), or namespace comparisons (that begin with '^'). Add a
convenience function to the refs.h API to detect when either of these
conditions are met, and returns an appropriate value to pass as excluded
patterns.
Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A future commit will want to call `for_each_namespaced_ref()` with
a list of excluded patterns.
We could introduce a variant of that function, say,
`for_each_namespaced_ref_exclude()` which takes the extra parameter, and
reimplement the original function in terms of that. But all but one
caller (in `http-backend.c`) will supply the new parameter, so add the
new parameter to `for_each_namespaced_ref()` itself instead of
introducing a new function.
For now, supply NULL for the list of excluded patterns at all callers to
avoid changing behavior, which we will do in a future change.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In subsequent commits, it will be convenient to have a 'const char **'
of hidden refs (matching `transfer.hiderefs`, `uploadpack.hideRefs`,
etc.), instead of a `string_list`.
Convert spots throughout the tree that store the list of hidden refs
from a `string_list` to a `strvec`.
Note that in `parse_hide_refs_config()` there is an ugly const-cast used
to avoid an extra copy of each value before trimming any trailing slash
characters. This could instead be written as:
ref = xstrdup(value);
len = strlen(ref);
while (len && ref[len - 1] == '/')
ref[--len] = '\0';
strvec_push(hide_refs, ref);
free(ref);
but the double-copy (once when calling `xstrdup()`, and another via
`strvec_push()`) is wasteful.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When iterating through the `packed-refs` file in order to answer a query
like:
$ git for-each-ref --exclude=refs/__hidden__
it would be useful to avoid walking over all of the entries in
`refs/__hidden__/*` when possible, since we know that the ref-filter
code is going to throw them away anyways.
In certain circumstances, doing so is possible. The algorithm for doing
so is as follows:
- For each excluded pattern, find the first record that matches it,
and the first record that *doesn't* match it (i.e. the location
you'd next want to consider when excluding that pattern).
- Sort the set of excluded regions from the previous step in ascending
order of the first location within the `packed-refs` file that
matches.
- Clean up the results from the previous step: discard empty regions,
and combine adjacent regions. The set of regions which remains is
referred to as the "jump list", and never contains any references
which should be included in the result set.
Then when iterating through the `packed-refs` file, if `iter->pos` is
ever contained in one of the regions from the previous steps, advance
`iter->pos` past the end of that region, and continue enumeration.
Note that we only perform this optimization when none of the excluded
pattern(s) have special meta-characters in them. For a pattern like
"refs/foo[ac]", the excluded regions ("refs/fooa", "refs/fooc", and
everything underneath them) are not connected. A future implementation
that handles this case may split the character class (pretending as if
two patterns were excluded: "refs/fooa", and "refs/fooc").
There are a few other gotchas worth considering. First, note that the
jump list is sorted, so once we jump past a region, we can avoid
considering it (or any regions preceding it) again. The member
`jump_pos` is used to track the first next-possible region to jump
through.
Second, note that the jump list is best-effort, since we do not handle
loose references, and because of the meta-character issue above. The
jump list may not skip past all references which won't appear in the
results, but will never skip over a reference which does appear in the
result set.
In repositories with a large number of hidden references, the speed-up
can be significant. Tests here are done with a copy of linux.git with a
reference "refs/pull/N" pointing at every commit, as in:
$ git rev-list HEAD | awk '{ print "create refs/pull/" NR " " $0 }' |
git update-ref --stdin
$ git pack-refs --all
, it is significantly faster to have `for-each-ref` jump over the
excluded references, as opposed to filtering them out after the fact:
$ hyperfine \
'git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"' \
'git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"' \
'git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"'
Benchmark 1: git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"
Time (mean ± σ): 798.1 ms ± 3.3 ms [User: 687.6 ms, System: 146.4 ms]
Range (min … max): 794.5 ms … 805.5 ms 10 runs
Benchmark 2: git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"
Time (mean ± σ): 98.9 ms ± 1.4 ms [User: 93.1 ms, System: 5.7 ms]
Range (min … max): 97.0 ms … 104.0 ms 29 runs
Benchmark 3: git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"
Time (mean ± σ): 4.5 ms ± 0.2 ms [User: 0.7 ms, System: 3.8 ms]
Range (min … max): 4.1 ms … 5.8 ms 524 runs
Summary
'git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"' ran
21.87 ± 1.05 times faster than 'git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"'
176.52 ± 8.19 times faster than 'git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"'
(Comparing stock git and this patch isn't quite fair, since an earlier
commit in this series adds a naive implementation of the `--exclude`
option. `git.prev` is built from the previous commit and includes this
naive implementation).
Using the jump list is fairly straightforward (see the changes to
`refs/packed-backend.c::next_record()`), but constructing the list is
not. To ensure that the construction is correct, add a new suite of
tests in t1419 covering various corner cases (overlapping regions,
partially overlapping regions, adjacent regions, etc.).
Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The subsequent patch will want to access an optional `excluded_patterns`
array within `refs/packed-backend.c` that will cull out certain
references matching any of the given patterns on a best-effort basis.
To do so, the refs subsystem needs to be updated to pass this value
across a number of different locations.
Prepare for a future patch by introducing this plumbing now, passing
NULLs at top-level APIs in order to make that patch less noisy and more
easily readable.
Signed-off-by: Taylor Blau <me@ttaylorr.co>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Allow users to be more selective over which refs to pack by adding an
--include option to git-pack-refs.
The existing options allow some measure of selectivity. By default
git-pack-refs packs all tags. --all can be used to include all refs,
and the previous commit added the ability to exclude certain refs with
--exclude.
While these knobs give the user some selection over which refs to pack,
it could be useful to give more control. For instance, a repository may
have a set of branches that are rarely updated and would benefit from
being packed. --include would allow the user to easily include a set of
branches to be packed while leaving everything else unpacked.
Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
At GitLab, we have a system that creates ephemeral internal refs that
don't live long before getting deleted. Having an option to exclude
certain refs from a packed-refs file allows these internal references to
be deleted much more efficiently.
Add an --exclude option to the pack-refs builtin, and use the ref
exclusions API to exclude certain refs from being packed into the final
packed-refs file
Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Split key function and data structure definitions out of cache.h to
new header files and adjust the users.
* en/header-split-cleanup:
csum-file.h: remove unnecessary inclusion of cache.h
write-or-die.h: move declarations for write-or-die.c functions from cache.h
treewide: remove cache.h inclusion due to setup.h changes
setup.h: move declarations for setup.c functions from cache.h
treewide: remove cache.h inclusion due to environment.h changes
environment.h: move declarations for environment.c functions from cache.h
treewide: remove unnecessary includes of cache.h
wrapper.h: move declarations for wrapper.c functions from cache.h
path.h: move function declarations for path.c functions from cache.h
cache.h: remove expand_user_path()
abspath.h: move absolute path functions from cache.h
environment: move comment_line_char from cache.h
treewide: remove unnecessary cache.h inclusion from several sources
treewide: remove unnecessary inclusion of gettext.h
treewide: be explicit about dependence on gettext.h
treewide: remove unnecessary cache.h inclusion from a few headers
Apply the part of "the_repository.pending.cocci" pertaining to
"refs.h".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Ever since a64215b6cd ("object.h: stop depending on cache.h; make
cache.h depend on object.h", 2023-02-24), we have a few headers that
could have replaced their include of cache.h with an include of
object.h. Make that change now.
Some C files had to start including cache.h after this change (or some
smaller header it had brought in), because the C files were depending
on things from cache.h but were only formerly implicitly getting
cache.h through one of these headers being modified in this patch.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The ls_refs() function (for the v2 protocol command of the same name)
takes a repository parameter (like all v2 commands), but ignores it. It
should use it to access the refs.
This isn't a bug in practice, since we only call this function when
serving upload-pack from the main repository. But it's an awkward
gotcha, and it causes -Wunused-parameter to complain.
The main reason we don't use the repository parameter is that the ref
iteration interface we call doesn't have a "refs_" variant that takes a
ref_store. However we can easily add one. In fact, since there is only
one other caller (in ref-filter.c), there is no need to maintain the
non-repository wrapper; that caller can just use the_repository. It's
still a long way from consistently using a repository object, but it's
one small step in the right direction.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We're about to add a new argument to git-rev-list(1) that allows it to
add all references that are visible when taking `transfer.hideRefs` et
al into account. This will require us to potentially parse multiple sets
of hidden refs, which is not easily possible right now as there is only
a single, global instance of the list of parsed hidden refs.
Refactor `parse_hide_refs_config()` and `ref_is_hidden()` so that both
take the list of hidden references as input and adjust callers to keep a
local list, instead. This allows us to easily use multiple hidden-ref
lists. Furthermore, it allows us to properly free this list before we
exit.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
The logic to handle worktree refs (worktrees/NAME/REF and
main-worktree/REF) existed in two places:
* ref_type() in refs.c
* parse_worktree_ref() in worktree.c
Collapse this logic together in one function parse_worktree_ref():
this avoids having to cross-check the result of parse_worktree_ref()
and ref_type().
Introduce enum ref_worktree_type, which is slightly different from
enum ref_type. The latter is a misleading name (one would think that
'ref_type' would have the symref option).
Instead, enum ref_worktree_type only makes explicit how a refname
relates to a worktree. From this point of view, HEAD and
refs/bisect/abc are the same: they specify the current worktree
implicitly.
The files-backend must avoid packing refs/bisect/* and friends into
packed-refs, so expose is_per_worktree_ref() separately.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git interprets different meanings to different refs based on their
names. Some meanings are cosmetic, like how refs in 'refs/remotes/*'
are colored differently from refs in 'refs/heads/*'. Others are more
critical, such as how replace refs are interpreted.
Before making behavior changes based on ref namespaces, collect all
known ref namespaces into a array of ref_namespace_info structs. This
array is indexed by the new ref_namespace enum for quick access.
As of this change, this array is purely documentation. Future changes
will add dependencies on this array.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reading of symbolic and non-symbolic references is currently treated the
same in reference backends: we always call `refs_read_raw_ref()` and
then decide based on the returned flags what type it is. This has one
downside though: symbolic references may be treated different from
normal references in a backend from normal references. The packed-refs
backend for example doesn't even know about symbolic references, and as
a result it is pointless to even ask it for one.
There are cases where we really only care about whether a reference is
symbolic or not, but don't care about whether it exists at all or may be
a non-symbolic reference. But it is not possible to optimize for this
case right now, and as a consequence we will always first check for a
loose reference to exist, and if it doesn't, we'll query the packed-refs
backend for a known-to-not-be-symbolic reference. This is inefficient
and requires us to search all packed references even though we know to
not care for the result at all.
Introduce a new function `refs_read_symbolic_ref()` which allows us to
fix this case. This function will only ever return symbolic references
and can thus optimize for the scenario layed out above. By default, if
the backend doesn't provide an implementation for it, we just use the
old code path and fall back to `read_raw_ref()`. But in case the backend
provides its own, more efficient implementation, we will use that one
instead.
Note that this function is explicitly designed to not distinguish
between missing references and non-symbolic references. If it did, we'd
be forced to always search the packed-refs backend to see whether the
symbolic reference the user asked for really doesn't exist, or if it
exists as a non-symbolic reference.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* ps/fetch-atomic:
fetch: make `--atomic` flag cover pruning of refs
fetch: make `--atomic` flag cover backfilling of tags
refs: add interface to iterate over queued transactional updates
fetch: report errors when backfilling tags fails
fetch: control lifecycle of FETCH_HEAD in a single place
fetch: backfill tags before setting upstream
fetch: increase test coverage of fetches
Because a deletion of ref would need to remove it from both the
loose ref store and the packed ref store, a delete-ref operation
that logically removes one ref may end up invoking ref-transaction
hook twice, which has been corrected.
* ps/avoid-unnecessary-hook-invocation-with-packed-refs:
refs: skip hooks when deleting uncovered packed refs
refs: do not execute reference-transaction hook on packing refs
refs: demonstrate excessive execution of the reference-transaction hook
refs: allow skipping the reference-transaction hook
refs: allow passing flags when beginning transactions
refs: extract packed_refs_delete_refs() to allow control of transaction
There is no way for a caller to see whether a reference update has
already been queued up for a given reference transaction. There are
multiple alternatives to provide this functionality:
- We may add a function that simply tells us whether a specific
reference has already been queued. If implemented naively then
this would potentially be quadratic in runtime behaviour if this
question is asked repeatedly because we have to iterate over all
references every time. The alternative would be to add a hashmap
of all queued reference updates to speed up the lookup, but this
adds overhead to all callers.
- We may add a flag to `ref_transaction_add_update()` that causes it
to skip duplicates, but this has the same runtime concerns as the
first alternative.
- We may add an interface which lets callers collect all updates
which have already been queued such that he can avoid re-adding
them. This is the most flexible approach and puts the burden on
the caller, but also allows us to not impact any of the existing
callsites which don't need this information.
This commit implements the last approach: it allows us to compute the
map of already-queued updates once up front such that we can then skip
all subsequent references which are already part of this map.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Remove the now-unused "failure_errno" parameter from the
refs_resolve_ref_unsafe() signature. In my recent 96f6623ada (Merge
branch 'ab/refs-errno-cleanup', 2021-11-29) series we made all of its
callers explicitly request the errno via an output parameter.
As that series shows all but one caller ended up passing in a
boilerplate "ignore_errno", since they only cared about whether the
return value was NULL or not, i.e. if the ref could be resolved.
There was one small issue with that series fixed with a follow-up in
31e3912369 (Merge branch 'ab/refs-errno-cleanup', 2022-01-14) a small
bug in that series was fixed.
After those two there was one caller left in sequencer.c that used the
"failure_errno', but as of the preceding commit it uses a boilerplate
"ignore_errno" instead.
This leaves the public refs API without any use of "failure_errno" at
all. We could still do with a bit of cleanup and generalization
between refs.c and refs/files-backend.c before the "reftable"
integration lands, but that's all internal to the reference code
itself.
So let's remove this output parameter. Not only isn't it used now, but
it's unlikely that we'll want it again in the future. We'd like to
slowly move the refs API to a more file-backend independent way of
communicating error codes, having it use a "failure_errno" was only
the first step in that direction. If this or any other function needs
to communicate what specifically is wrong with the requested "refname"
it'll be better to have the function set some output enum of
well-defined error states than piggy-backend on "errno".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The reference-transaction hook is executing whenever we prepare, commit
or abort a reference transaction. While this is mostly intentional, in
case of the files backend we're leaking the implementation detail that
the store is in fact a composite store with one loose and one packed
backend to the caller. So while we want to execute the hook for all
logical updates, executing it for such implementation details is
unexpected.
Prepare for a fix by adding a new flag which allows to skip execution of
the hook.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We do not currently have any flags when creating reference transactions,
but we'll add one to disable execution of the reference transaction hook
in some cases.
Allow passing flags to `ref_store_transaction_begin()` to prepare for
this change.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the handling of the "verbose" flag entirely out of
"refs/files-backend.c" and into "builtin/reflog.c". This allows the
backend to stop knowing about the EXPIRE_REFLOGS_VERBOSE flag.
The expire_reflog_ent() function shouldn't need to deal with the
implementation detail of whether or not we're emitting verbose output,
by doing this the --verbose output becomes backend-agnostic, so
reftable will get the same output.
I think the output is rather bad currently, and should e.g. be
implemented with some better future mode of progress.[ch], but that's
a topic for another improvement.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The test helper for refs subsystem learned to write bogus and/or
nonexistent object name to refs to simulate error situations we
want to test Git in.
* hn/allow-bogus-oid-in-ref-tests:
t1430: create valid symrefs using test-helper
t1430: remove refs using test-tool
refs: introduce REF_SKIP_REFNAME_VERIFICATION flag
refs: introduce REF_SKIP_OID_VERIFICATION flag
refs: update comment.
test-ref-store: plug memory leak in cmd_delete_refs
test-ref-store: parse symbolic flag constants
test-ref-store: remove force-create argument for create-reflog
Document the parameters given to the reflog entry iterator callback
functions.
* jc/reflog-iterator-callback-doc:
refs: document callback for reflog-ent iterators
Use this flag with the test-helper in t1430, to avoid direct writes to the ref
database.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This lets the ref-store test helper write non-existent or unparsable objects
into the ref storage.
Use this to make t1006 and t3800 independent of the files storage backend.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs_for_each_reflog_ent() and refs_for_each_reflog_ent_reverse()
functions take a callback function that gets called with the details
of each reflog entry. Its parameters were not documented beyond
their names. Elaborate a bit on each of them.
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There is only one caller, builtin/checkout.c, and it hardcodes
force_create=1.
This argument was introduced in abd0cd3a30 (refs: new public ref function:
safe_create_reflog, 2015-07-21), which promised to immediately use it in a
follow-on commit, but that never happened.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rename the transitory refs_werrres_ref_unsafe() function to
refs_resolve_ref_unsafe(), now that all callers of the old function
have learned to pass in a "failure_errno" parameter.
The coccinelle semantic patch added in the preceding commit works, but
I couldn't figure out how to get spatch(1) to re-flow these argument
lists (and sometimes make lines way too long), so this rename was done
with:
perl -pi -e 's/refs_werrres_ref_unsafe/refs_resolve_ref_unsafe/g' \
$(git grep -l refs_werrres_ref_unsafe -- '*.c')
But after that "make contrib/coccinelle/refs.cocci.patch" comes up
empty, so the result would have been the same. Let's remove that
transitory semantic patch file, we won't need to retain it for any
other in-flight changes, refs_werrres_ref_unsafe() only existed within
this patch series.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In preceding commits all callers of refs_resolve_ref_unsafe() were
migrated to the transitory refs_werrres_ref_unsafe() function.
As a first step in getting rid of it let's remove the old function
from the public API (it went unused in a preceding commit).
We then provide both a coccinelle rule to do the rename, and a macro
to avoid breaking the existing callers.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Remove the refs_read_ref_full() wrapper in favor of migrating various
refs.c API users to the underlying refs_werrres_ref_unsafe() function.
A careful reading of these callers shows that the callers of this
function did not care about "errno", by moving away from the
refs_resolve_ref_unsafe() wrapper we can be sure that nothing relies
on it anymore.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a new refs_werrres_ref_unsafe() function, which is like
refs_resolve_ref_unsafe() except that it explicitly saves away the
"errno" to a passed-in parameter, the refs_resolve_ref_unsafe() then
becomes a wrapper for it.
In subsequent commits we'll migrate code over to it, before finally
making "refs_resolve_ref_unsafe()" with an "errno" parameter the
canonical version, so this this function exists only so that we can
incrementally migrate callers, it will be going away in a subsequent
commit.
As the added comment notes has a rather tortured name to be the same
length as "refs_resolve_ref_unsafe", to avoid churn as we won't need
to re-indent the argument lists, similarly the documentation and
structure of it in refs.h is designed to minimize a diff in a
subsequent commit, where that documentation will be added to the new
refs_resolve_ref_unsafe().
At the end of this migration the "meaningful errno" TODO item left in
76d70dc0c6 (refs.c: make resolve_ref_unsafe set errno to something
meaningful on error, 2014-06-20) will be resolved.
As can be seen from the use of refs_read_raw_ref() we'll also need to
convert some functions that the new refs_werrres_ref_unsafe() itself
calls to take this "failure_errno". That will be done in subsequent
commits.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The ref iteration code used to optionally allow dangling refs to be
shown, which has been tightened up.
* jk/ref-paranoia:
refs: drop "broken" flag from for_each_fullref_in()
ref-filter: drop broken-ref code entirely
ref-filter: stop setting FILTER_REFS_INCLUDE_BROKEN
repack, prune: drop GIT_REF_PARANOIA settings
refs: turn on GIT_REF_PARANOIA by default
refs: omit dangling symrefs when using GIT_REF_PARANOIA
refs: add DO_FOR_EACH_OMIT_DANGLING_SYMREFS flag
refs-internal.h: reorganize DO_FOR_EACH_* flag documentation
refs-internal.h: move DO_FOR_EACH_* flags next to each other
t5312: be more assertive about command failure
t5312: test non-destructive repack
t5312: create bogus ref as necessary
t5312: drop "verbose" helper
t5600: provide detached HEAD for corruption failures
t5516: don't use HEAD ref for invalid ref-deletion tests
t7900: clean up some more broken refs
This function was added in 3dce444f17 (refs: add a backend method
structure, 2016-09-04), but has never been used by anything. The only
caller that might care uses find_ref_storage_backend() directly.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
No callers pass in anything but "0" here. Likewise to our sibling
functions. Note that some of them ferry along the flag, but none of
their callers pass anything but "0" either.
Nor is anybody likely to change that. Callers which really want to see
all of the raw refs use for_each_rawref(). And anybody interested in
iterating a subset of the refs will likely be happy to use the
now-default behavior of showing broken refs, but omitting dangling
symlinks.
So we can get rid of this whole feature.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since the the preceding commit the "oid" parameter to reflog_expire()
is always NULL, but it was not cleaned up to reduce the size of the
diff. Let's do that subsequent API and documentation cleanup now.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
During reflog expiry, the cmd_reflog_expire() function first iterates
over all reflogs in logs/*, and then one-by-one acquires the lock for
each one and expires it. This behavior has been with us since this
command was implemented in 4264dc15e1 ("git reflog expire",
2006-12-19).
Change this to stop calling lock_ref_oid_basic() with the OID we saw
when we looped over the logs, instead have it pass the OID it managed
to lock.
This mostly mitigates a race condition where e.g. "git gc" will fail
in a concurrently updated repository because the branch moved since
"git reflog expire --all" was started. I.e. with:
error: cannot lock ref '<refname>': ref '<refname>' is at <OID-A> but expected <OID-B>
This behavior of passing in an "oid" was needed for an edge-case that
I've untangled in this and preceding commits though, namely that we
needed this OID because we'd:
1. Lookup the reflog name/OID via dwim_log()
2. With that OID, lock the reflog
3. Later in builtin/reflog.c we use the OID we looked as input to
lookup_commit_reference_gently(), assured that it's equal to the
OID we got from dwim_log().
We can be sure that this change is safe to make because between
dwim_log (step #1) and lock_ref_oid_basic (step #2) there was no other
logic relevant to the OID or expiry run in the cmd_reflog_expire()
caller.
We can thus treat that code as a black box, before and after this
change it would get an OID that's been locked, the only difference is
that now we mostly won't be failing to get the lock due to the TOCTOU
race[0]. That failure was purely an implementation detail in how the
"current OID" was looked up, it was divorced from the locking
mechanism.
What do we mean with "mostly"? It mostly mitigates it because we'll
still run into cases where the ref is locked and being updated as we
want to expire it, and other git processes wanting to update the refs
will in turn race with us as we expire the reflog.
That remaining race can in turn be mitigated with the
core.filesRefLockTimeout setting, see 4ff0f01cb7 ("refs: retry
acquiring reference locks for 100ms", 2017-08-21). In practice if that
value is high enough we'll probably never have ref updates or reflog
expiry failing, since the clients involved will retry for far longer
than the time any of those operations could take.
See [1] for an initial report of how this impacted "git gc" and a
large discussion about this change in early 2019. In particular patch
looked good to Michael Haggerty, see his[2]. That message seems to not
have made it to the ML archive, its content is quoted in full in my
[3].
I'm leaving behind now-unused code the refs API etc. that takes the
now-NULL "unused_oid" argument, and other code that can be simplified now
that we never have on OID in that context, that'll be cleaned up in
subsequent commits, but for now let's narrowly focus on fixing the
"git gc" issue. As the modified assert() shows we always pass a NULL
oid to reflog_expire() now.
Unfortunately this sort of probabilistic contention is hard to turn
into a test. I've tested this by running the following three subshells
in concurrent terminals:
(
rm -rf /tmp/git &&
git init /tmp/git &&
while true
do
head -c 10 /dev/urandom | hexdump >/tmp/git/out &&
git -C /tmp/git add out &&
git -C /tmp/git commit -m"out"
done
)
(
rm -rf /tmp/git-clone &&
git clone file:///tmp/git /tmp/git-clone &&
while git -C /tmp/git-clone pull
do
date
done
)
(
while git -C /tmp/git-clone reflog expire --all
do
date
done
)
Before this change the "reflog expire" would fail really quickly with
the "but expected" error noted above.
After this change both the "pull" and "reflog expire" will run for a
while, but eventually fail because I get unlucky with
core.filesRefLockTimeout (the "reflog expire" is in a really tight
loop). As noted above that can in turn be mitigated with higher values
of core.filesRefLockTimeout than the 100ms default.
As noted in the commentary added in the preceding commit there's also
the case of branches being racily deleted, that can be tested by
adding this to the above:
(
while git -C /tmp/git-clone branch topic master &&
git -C /tmp/git-clone branch -D topic
do
date
done
)
With core.filesRefLockTimeout set to 10 seconds (it can probably be a
lot lower) I managed to run all four of these concurrently for about
an hour, and accumulated ~125k commits, auto-gc's and all, and didn't
have a single failure. The loops visibly stall while waiting for the
lock, but that's expected and desired behavior.
0. https://en.wikipedia.org/wiki/Time-of-check_to_time-of-use
1. https://lore.kernel.org/git/87tvg7brlm.fsf@evledraar.gmail.com/
2. http://lore.kernel.org/git/b870a17d-2103-41b8-3cbc-7389d5fff33a@alum.mit.edu
3. https://lore.kernel.org/git/87pnqkco8v.fsf@evledraar.gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The ls-refs protocol operation has been optimized to narrow the
sub-hierarchy of refs/ it walks to produce response.
* tb/ls-refs-optim:
ls-refs.c: traverse prefixes of disjoint "ref-prefix" sets
ls-refs.c: initialize 'prefixes' before using it
refs: expose 'for_each_fullref_in_prefixes'
This function was used in the ref-filter.c code to find the longest
common prefix of among a set of refspecs, and then to iterate all of the
references that descend from that prefix.
A future patch will want to use that same code from ls-refs.c, so
prepare by exposing and moving it to refs.c. Since there is nothing
specific to the ref-filter code here (other than that it was previously
the only caller of this function), this really belongs in the more
generic refs.h header.
The code moved in this patch is identical before and after, with the one
exception of renaming some arguments to be consistent with other
functions exposed in refs.h.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The peel_ref() interface is confusing and error-prone:
- it's typically used by ref iteration callbacks that have both a
refname and oid. But since they pass only the refname, we may load
the ref value from the filesystem again. This is inefficient, but
also means we are open to a race if somebody simultaneously updates
the ref. E.g., this:
int some_ref_cb(const char *refname, const struct object_id *oid, ...)
{
if (!peel_ref(refname, &peeled))
printf("%s peels to %s",
oid_to_hex(oid), oid_to_hex(&peeled);
}
could print nonsense. It is correct to say "refname peels to..."
(you may see the "before" value or the "after" value, either of
which is consistent), but mentioning both oids may be mixing
before/after values.
Worse, whether this is possible depends on whether the optimization
to read from the current iterator value kicks in. So it is actually
not possible with:
for_each_ref(some_ref_cb);
but it _is_ possible with:
head_ref(some_ref_cb);
which does not use the iterator mechanism (though in practice, HEAD
should never peel to anything, so this may not be triggerable).
- it must take a fully-qualified refname for the read_ref_full() code
path to work. Yet we routinely pass it partial refnames from
callbacks to for_each_tag_ref(), etc. This happens to work when
iterating because there we do not call read_ref_full() at all, and
only use the passed refname to check if it is the same as the
iterator. But the requirements for the function parameters are quite
unclear.
Instead of taking a refname, let's instead take an oid. That fixes both
problems. It's a little funny for a "ref" function not to involve refs
at all. The key thing is that it's optimizing under the hood based on
having access to the ref iterator. So let's change the name to make it
clear why you'd want this function versus just peel_object().
There are two other directions I considered but rejected:
- we could pass the peel information into the each_ref_fn callback.
However, we don't know if the caller actually wants it or not. For
packed-refs, providing it is essentially free. But for loose refs,
we actually have to peel the object, which would be wasteful in most
cases. We could likewise pass in a flag to the callback indicating
whether the peeled information is known, but that complicates those
callbacks, as they then have to decide whether to manually peel
themselves. Plus it requires changing the interface of every
callback, whether they care about peeling or not, and there are many
of them.
- we could make a function to return the peeled value of the current
iterated ref (computing it if necessary), and BUG() otherwise. I.e.:
int peel_current_iterated_ref(struct object_id *out);
Each of the current callers is an each_ref_fn callback, so they'd
mostly be happy. But:
- we use those callbacks with functions like head_ref(), which do
not use the iteration code. So we'd need to handle the fallback
case there, anyway.
- it's possible that a caller would want to call into generic code
that sometimes is used during iteration and sometimes not. This
encapsulates the logic to do the fast thing when possible, and
fallback when necessary.
The implementation is mostly obvious, but I want to call out a few
things in the patch:
- the test-tool coverage for peel_ref() is now meaningless, as it all
collapses to a single peel_object() call (arguably they were pretty
uninteresting before; the tricky part of that function is the
fast-path we see during iteration, but these calls didn't trigger
that). I've just dropped it entirely, though note that some other
tests relied on the tags we created; I've moved that creation to the
tests where it matters.
- we no longer need to take a ref_store parameter, since we'd never
look up a ref now. We do still rely on a global "current iterator"
variable which _could_ be kept per-ref-store. But in practice this
is only useful if there are multiple recursive iterations, at which
point the more appropriate solution is probably a stack of
iterators. No caller used the actual ref-store parameter anyway
(they all call the wrapper that passes the_repository).
- the original only kicked in the optimization when the "refname"
pointer matched (i.e., not string comparison). We do likewise with
the "oid" parameter here, but fall back to doing an actual oideq()
call. This in theory lets us kick in the optimization more often,
though in practice no current caller cares. It should never be
wrong, though (peeling is a property of an object, so two refs
pointing to the same object would peel identically).
- the original took care not to touch the peeled out-parameter unless
we found something to put in it. But no caller cares about this, and
anyway, it is enforced by peel_object() itself (and even in the
optimized iterator case, that's where we eventually end up). We can
shorten the code and avoid an extra copy by just passing the
out-parameter through the stack.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Junio C Hamano
Patrick Steinhardt
Taylor Blau
John Cai
Ævar Arnfjörð Bjarmason
Elijah Newren
Jeff King
Han-Wen Nienhuys
Derrick Stolee