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The consistency checks for the files reference backend have been updated
to skip lock files earlier, avoiding unnecessary parsing of
intermediate files.
* kn/refs-fsck-skip-lock-files:
refs/files: skip lock files during consistency checks
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Refactor service routines in the ref subsystem backends.
* kn/refs-generic-helpers:
refs: use peeled tag values in reference backends
refs: add peeled object ID to the `ref_update` struct
refs: move object parsing to the generic layer
update-ref: handle rejections while adding updates
update-ref: move `print_rejected_refs()` up
refs: return `ref_transaction_error` from `ref_transaction_update()`
refs: extract out reflog config to generic layer
refs: introduce `ref_store_init_options`
refs: remove unused typedef 'ref_transaction_commit_fn'
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Consistency checks in the files reference backend involve two steps:
1. Iterate over all entries within the 'refs/' directory and call
`files_fsck_ref()` on each.
2. Iterate over all root refs via `for_each_root_ref()` and call
`files_fsck_ref()` on each.
`files_fsck_ref()` then runs all fsck checks defined in
`fsck_refs_fn[]`. Step 2 goes through the refs API and only sees valid
refs, but step 1 iterates the directory directly and may also encounter
intermediate '*.lock' files.
Currently, `files_fsck_refs_name()`, one of the functions in
`fsck_refs_fn[]`, filters out lock files itself. The other function,
`files_fsck_refs_content()`, has no such check and would parse the lock
file. Any new function added to `fsck_refs_fn[]` would have the same
problem.
Move the filter up into `files_fsck_refs_dir()`, where the directory
iteration happens. Since step 2 cannot produce lock files, this is the
only site where the filter is needed, and individual checks no longer
have to re-implement it.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Code clean-up to use the right instance of a repository instance in
calls inside refs subsystem.
* sp/refs-reduce-the-repository:
refs/reftable-backend: drop uses of the_repository
refs: remove the_hash_algo global state
refs: add struct repository parameter in get_files_ref_lock_timeout_ms()
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The reference backends peel tag objects when storing references to them.
This is to provide optimized reads which avoids hitting the odb. The
previous commits ensures that the peeled value is now propagated via the
generic layer. So modify the packed and reftable backend to directly use
this value instead of calling `peel_object()` independently.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Certain reference backends {packed, reftable}, have the ability to also
store the peeled object ID for a reference pointing to a tag object.
This has the added benefit that during retrieval of such references, we
also obtain the peeled object ID without having to use the ODB.
To provide this functionality, each backend independently calls the ODB
to obtain the peeled OID. To move this functionality to the generic
layer, there must be support infrastructure to pass in a peeled OID for
reference updates.
Add a `peeled` field to the `ref_update` structure and modify
`ref_transaction_add_update()` to receive and copy this object ID to the
`ref_update` structure. Finally, modify `ref_transaction_update()` to
peel tag objects and pass the peeled OID to
`ref_transaction_add_update()`.
Update all callers of these functions with the new function parameters.
Callers which only add reflog updates, need to only pass in NULL, since
for reflogs, we don't store peeled OIDs. Reference deletions also only
need to pass in NULL. For others, pass along the peeled OID if
available.
In a following commit, we'll modify the backends to use this peeled OID
instead of parsing it themselves.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Regular reference updates made via reference transactions validate that
the provided object ID exists in the object database, which is done by
calling 'parse_object()'. This check is done independently by the
backends which leads to duplicated logic.
Let's move this to the generic layer, ensuring the backends only have to
care about reference storage and not about validation of the object IDs.
With this also remove the 'REF_TRANSACTION_ERROR_INVALID_NEW_VALUE'
error type as its no longer used.
Since we don't iterate over individual references in
`ref_transaction_prepare()`, we add this check to
`ref_transaction_update()`. This means that the validation is done as
soon as an update is queued, without needing to prepare the
transaction. It can be argued that this is more ideal, since this
validation has no dependency on the reference transaction being
prepared.
It must be noted that the change in behavior means that this error
cannot be ignored even with usage of batched updates, since this happens
when the update is being added to the transaction. But since the caller
gets specific error codes, they can either abort the transaction or
continue adding other updates to the transaction.
Modify 'builtin/receive-pack.c' to now capture the error type so that
the error propagated to the client stays the same. Also remove two of
the tests which validates batch-updates with invalid new_oid.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The reference backends need to know when to create reflog entries, this
is dictated by the 'core.logallrefupdates' config. Instead of relying on
the backends to call `repo_settings_get_log_all_ref_updates()` to obtain
this config value, let's do this in the generic layer and pass down the
value to the backends.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Reference backends are initiated via the `init()` function. When
initiating the function, the backend is also provided flags which denote
the access levels of the initiator. Create a new structure
`ref_store_init_options` to house such options and move the access flags
to this structure.
This allows easier extension of providing further options to the
backends. In the following commit, we'll also provide config around
reflog creation to the backends via the same structure.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The typedef 'ref_transaction_commit_fn' is not used anywhere in our
code, let's remove it.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Further work to adjust the codebase for C23 that changes functions
like strchr() that discarded constness when they return a pointer into
a const string to preserve constness.
* jk/c23-const-preserving-fixes-more:
git-compat-util: fix CONST_OUTPARAM typo and indentation
refs/files-backend: drop const to fix strchr() warning
http: drop const to fix strstr() warning
range-diff: drop const to fix strstr() warnings
pkt-line: make packet_reader.line non-const
skip_prefix(): check const match between in and out params
pseudo-merge: fix disk reads from find_pseudo_merge()
find_last_dir_sep(): convert inline function to macro
run-command: explicitly cast away constness when assigning to void
pager: explicitly cast away strchr() constness
transport-helper: drop const to fix strchr() warnings
http: add const to fix strchr() warnings
convert: add const to fix strchr() warnings
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Update reftable library part with what is used in libgit2 to improve
portability to different target codebases and platforms.
* ps/reftable-portability:
reftable/system: add abstraction to mmap files
reftable/system: add abstraction to retrieve time in milliseconds
reftable/fsck: use REFTABLE_UNUSED instead of UNUSED
reftable/stack: provide fsync(3p) via system header
reftable: introduce "reftable-system.h" header
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reftable_be_init() and reftable_be_create_on_disk() use the_repository even
though a repository instance is already available, either directly or via
struct ref_store.
Replace these uses with the appropriate local repository instance (repo or
ref_store->repo) to avoid relying on global state.
Note that USE_THE_REPOSITORY_VARIABLE cannot be removed yet, as
is_bare_repository() is still there in the file.
Signed-off-by: Shreyansh Paliwal <shreyanshpaliwalcmsmn@gmail.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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get_files_ref_lock_timeout_ms() calls repo_config_get_int() using
the_repository, as no repository instance is available in its scope. Add a
struct repository parameter and use it instead of the_repository.
Update all callers accordingly. In files-backend.c, lock_raw_ref() can
obtain repository instance from the struct ref_transaction via
transaction->ref_store->repo and pass it down. For create_reflock(), which
is used as a callback, introduce a small wrapper struct to pass both struct
lock_file and struct repository through the callback data.
This reduces reliance on the_repository global, though the function
still uses static variables and is not yet fully repository-scoped.
This can be addressed in a follow-up change.
Signed-off-by: Shreyansh Paliwal <shreyanshpaliwalcmsmn@gmail.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Users of the reftable library are expected to provide their own function
callback in cases they want to sync(3p) data to disk via the reftable
write options. But if no such function was provided we end up calling
fsync(3p) directly, which may not even be available on some systems.
While dropping the explicit call to fsync(3p) would work, it would lead
to an unsafe default behaviour where a project may have forgotten to set
up the callback function, and that could lead to potential data loss. So
this is not a great solution.
Instead, drop the callback function and make it mandatory for the
project to define fsync(3p). In the case of Git, we can then easily
inject our custom implementation via the "reftable-system.h" header so
that we continue to use `fsync_component()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In show_one_reflog_ent(), we're fed a writable strbuf buffer, which we
parse into the various reflog components. We write a NUL over email_end
to tie off one of the fields, and thus email_end must be non-const.
But with a C23 implementation of libc, strchr() will now complain when
assigning the result to a non-const pointer from a const one. So we can
fix this by making the source pointer non-const.
But there's a catch. We derive that source pointer by parsing the line
with parse_oid_hex_algop(), which requires a const pointer for its
out-parameter. We can work around that by teaching it to use our
CONST_OUTPARAM() trick, just like skip_prefix().
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The HTTP transport learned to react to "429 Too Many Requests".
* vp/http-rate-limit-retries:
http: add support for HTTP 429 rate limit retries
strbuf_attach: fix call sites to pass correct alloc
strbuf: pass correct alloc to strbuf_attach() in strbuf_reencode()
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strbuf_attach(sb, buf, len, alloc) requires alloc > len (the buffer
must have at least len+1 bytes to hold the NUL). Several call sites
passed alloc == len, relying on strbuf_grow(sb, 0) inside strbuf_attach
to reallocate. Fix these in mailinfo, am, refs/files-backend,
fast-import, and trailer by passing len+1 when the buffer is a
NUL-terminated string (or from strbuf_detach).
Signed-off-by: Vaidas Pilkauskas <vaidas.pilkauskas@shopify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Code refactoring around refs-for-each-* API functions.
* ps/refs-for-each:
refs: replace `refs_for_each_fullref_in()`
refs: replace `refs_for_each_namespaced_ref()`
refs: replace `refs_for_each_glob_ref()`
refs: replace `refs_for_each_glob_ref_in()`
refs: replace `refs_for_each_rawref_in()`
refs: replace `refs_for_each_rawref()`
refs: replace `refs_for_each_ref_in()`
refs: improve verification for-each-ref options
refs: generalize `refs_for_each_fullref_in_prefixes()`
refs: generalize `refs_for_each_namespaced_ref()`
refs: speed up `refs_for_each_glob_ref_in()`
refs: introduce `refs_for_each_ref_ext`
refs: rename `each_ref_fn`
refs: rename `do_for_each_ref_flags`
refs: move `do_for_each_ref_flags` further up
refs: move `refs_head_ref_namespaced()`
refs: remove unused `refs_for_each_include_root_ref()`
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Allow the directory in which reference backends store their data to
be specified.
* kn/ref-location:
refs: add GIT_REFERENCE_BACKEND to specify reference backend
refs: allow reference location in refstorage config
refs: receive and use the reference storage payload
refs: move out stub modification to generic layer
refs: extract out `refs_create_refdir_stubs()`
setup: don't modify repo in `create_reference_database()`
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An upcoming commit will add support for providing an URI via the
'extensions.refStorage' config. The URI will contain the reference
backend and a corresponding payload. The payload can be then used for
providing an alternate locations for the reference backend.
To prepare for this, modify the existing backends to accept such an
argument when initializing via the 'init()' function. Both the files
and reftable backends will parse the information to be filesystem paths
to store references. Given that no callers pass any payload yet this is
essentially a no-op change for now.
To enable this, provide a 'refs_compute_filesystem_location()' function
which will parse the current 'gitdir' and the 'payload' to provide the
final reference directory and common reference directory (if working in
a linked worktree).
The documentation and tests will be added alongside the extension of the
config variable.
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When creating the reftable reference backend on disk, we create stubs to
ensure that the directory can be recognized as a Git repository. This is
done by calling `refs_create_refdir_stubs()`. Move this to the generic
layer as this is needed for all backends excluding from the files
backends. In an upcoming commit where we introduce alternate reference
backend locations, we'll have to also create stubs in the $GIT_DIR
irrespective of the backend being used. This commit builds the base to
add that logic.
Similarly, move the logic for deletion of stubs to the generic layer.
The files backend recursively calls the remove function of the
'packed-backend', here skip calling the generic function since that
would try to delete stubs.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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For Git to recognize a directory as a Git directory, it requires the
directory to contain:
1. 'HEAD' file
2. 'objects/' directory
3. 'refs/' directory
Here, #1 and #3 are part of the reference storage mechanism,
specifically the files backend. Since then, newer backends such as the
reftable backend have moved to using their own path ('reftable/') for
storing references. But to ensure Git still recognizes the directory as
a Git directory, we create stubs.
There are two locations where we create stubs:
- In 'refs/reftable-backend.c' when creating the reftable backend.
- In 'clone.c' before spawning transport helpers.
In a following commit, we'll add another instance. So instead of
repeating the code, let's extract out this code to
`refs_create_refdir_stubs()` and use it.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Replace calls to `refs_for_each_rawref()` with the newly introduced
`refs_for_each_ref_ext()` function.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Similar to the preceding commit, rename `each_ref_fn` to better match
our current best practices around how we name things.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The enum `do_for_each_ref_flags` and its individual values don't match
to our current best practices when it comes to naming things. Rename it
to `refs_for_each_flag`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A handful of code paths that started using batched ref update API
(after Git 2.51 or so) lost detailed error output, which have been
corrected.
* kn/ref-batch-output-error-reporting-fix:
fetch: delay user information post committing of transaction
receive-pack: utilize rejected ref error details
fetch: utilize rejected ref error details
update-ref: utilize rejected error details if available
refs: add rejection detail to the callback function
refs: skip to next ref when current ref is rejected
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In `refs_verify_refnames_available()` we have two nested loops: the
outer loop iterates over all references to check, while the inner loop
checks for filesystem conflicts for a given ref by breaking down its
path.
With batched updates, when we detect a filesystem conflict, we mark the
update as rejected and execute 'continue'. However, this only skips to
the next iteration of the inner loop, not the outer loop as intended.
This causes the same reference to be repeatedly rejected. Fix this by
using a goto statement to skip to the next reference in the outer loop.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In a preceding commit we have extracted generic checks for both direct
and symbolic refs that apply for all backends. Wire up those checks for
the "reftable" backend.
Note that this is done by iterating through all refs manually with the
low-level reftable ref iterator. We explicitly don't want to use the
higher-level iterator that is exposed to users of the reftable backend
as that iterator may swallow for example broken refs.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The ref consistency checks are driven via `cmd_refs_verify()`. That
function loops through all worktrees (including the main worktree) and
then checks the ref store for each of them individually. It follows that
the backend is expected to only verify refs that belong to the specified
worktree.
While the "files" backend handles this correctly, the "reftable" backend
doesn't. In fact, it completely ignores the passed worktree and instead
verifies refs of _all_ worktrees. The consequence is that we'll end up
every ref store N times, where N is the number of worktrees.
Or rather, that would be the case if we actually iterated through the
worktree reftable stacks correctly. But we use `strmap_for_each_entry()`
to iterate through the stacks, but the map is in fact not even properly
populated. So instead of checking stacks N^2 times, we actually only end
up checking the reftable stack of the main worktree.
Fix this bug by only verifying the stack of the passed-in worktree and
constructing the backends via `backend_for_worktree()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Pull out the logic to retrieve a backend for a given worktree. This
function will be used in a subsequent commit.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Adapt the includes to be sorted and to use include paths that are
relative to the "refs/" directory.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In a subsequent commit we'll introduce new generic checks for direct
refs. These checks will be independent of the actual backend.
Introduce a new function `refs_fsck_ref()` that will be used for this
purpose. At the current point in time it's still empty, but it will get
populated in a subsequent commit.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The consistency checks for the "files" backend contain a couple of
verifications for symrefs that verify generic properties of the target
reference. These properties need to hold for every backend, no matter
whether it's using the "files" or "reftable" backend.
Reimplementing these checks for every single backend doesn't really make
sense. Extract it into a generic `refs_fsck_symref()` function that can
be used by other backends, as well. The "reftable" backend will be wired
up in a subsequent commit.
While at it, improve the consistency checks so that we don't complain
about refs pointing to a non-ref target in case the target refname
format does not verify. Otherwise it's very likely that we'll generate
both error messages, which feels somewhat redundant in this case.
Note that the function has a couple of `UNUSED` parameters. These will
become referenced in a subsequent commit.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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While the "files" backend already knows to perform consistency checks
for the "refs/" hierarchy, it doesn't verify any of its root refs. Plug
this omission.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The error handling when verifying symbolic refs is a bit on the wild
side:
- `fsck_report_ref()` can be told to ignore specific errors. If an
error has been ignored and a previous check raised an unignored
error, then assigning `ret = fsck_report_ref()` will cause us to
swallow the previous error.
- When the target reference is not valid we bail out early without
checking for other errors.
Fix both of these issues by consistently or'ing the return value and not
bailing out early.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When checking the consistency of references we create a directory
iterator and then verify each single reference in a loop. The logic to
perform the actual checks is embedded into that loop, which makes it
hard to reuse. But In a subsequent commit we're about to introduce a
second path that wants to verify references.
Prepare for this by extracting the logic to check a single reference
into a standalone function.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The function `files_fsck_refs()` only has a single callsite and forwards
all of its arguments as-is, so it's basically a useless indirection.
Inline the function call.
While at it, also remove the bitwise or that we have for return values.
We don't really want to or them at all, but rather just want to return
an error in case either of the functions has failed.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The parameter `refs_check_dir` determines which directory we want to
check references for. But as we always want to check the complete
refs hierarchy, this parameter is always set to "refs".
Drop the parameter and hardcode it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When performing consistency checks we pass the functions that perform
the verification down the calling stack. This is somewhat unnecessary
though, as the set of functions doesn't ever change.
Simplify the code by moving the array into global scope and remove the
parameter.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When iterating through root refs we first need to determine the
directory in which the refs live. This is done by retrieving the root of
the loose refs via `refs->loose->root->name`, and putting it through
`files_ref_path()` to derive the final path.
This is somewhat redundant though: the root name of the loose files
cache is always going to be the empty string. As such, we always end up
passing that empty string to `files_ref_path()` as the ref hierarchy we
want to start. And this actually makes sense: `files_ref_path()` already
computes the location of the root directory, so of course we need to
pass the empty string for the ref hierarchy itself. So going via the
loose ref cache to figure out that the root of a ref hierarchy is empty
is only causing confusion.
But next to the added confusion, it can also lead to a segfault. The
loose ref cache is populated lazily, so it may not always be set. It
seems to be sheer luck that this is a condition we do not currently hit.
The right thing to do would be to call `get_loose_ref_cache()`, which
knows to populate the cache if required.
Simplify the code and fix the potential segfault by simply removing the
indirection via the loose ref cache completely.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Brown-paper-bag fix to a recently graduated
'kn/maintenance-is-needed' topic.
* gf/maintenance-is-needed-fix:
refs: dereference the value of the required pointer
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Currently, this always prints yes because required is non-null.
This is the wrong behavior. The boolean must be
dereferenced.
Signed-off-by: Greg Funni <gfunni234@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git maintenance" command learned "is-needed" subcommand to tell if
it is necessary to perform various maintenance tasks.
* kn/maintenance-is-needed:
maintenance: add 'is-needed' subcommand
maintenance: add checking logic in `pack_refs_condition()`
refs: add a `optimize_required` field to `struct ref_storage_be`
reftable/stack: add function to check if optimization is required
reftable/stack: return stack segments directly
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Another fix-up to "peeled-tags" topic.
* ps/ref-peeled-tags-fixes:
object: fix performance regression when peeling tags
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Code clean-up.
* kn/refs-optim-cleanup:
t/pack-refs-tests: move the 'test_done' to callees
refs: rename 'pack_refs_opts' to 'refs_optimize_opts'
refs: move to using the '.optimize' functions
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Some ref backend storage can hold not just the object name of an
annotated tag, but the object name of the object the tag points at.
The code to handle this information has been streamlined.
* ps/ref-peeled-tags:
t7004: do not chdir around in the main process
ref-filter: fix stale parsed objects
ref-filter: parse objects on demand
ref-filter: detect broken tags when dereferencing them
refs: don't store peeled object IDs for invalid tags
object: add flag to `peel_object()` to verify object type
refs: drop infrastructure to peel via iterators
refs: drop `current_ref_iter` hack
builtin/show-ref: convert to use `reference_get_peeled_oid()`
ref-filter: propagate peeled object ID
upload-pack: convert to use `reference_get_peeled_oid()`
refs: expose peeled object ID via the iterator
refs: refactor reference status flags
refs: fully reset `struct ref_iterator::ref` on iteration
refs: introduce `.ref` field for the base iterator
refs: introduce wrapper struct for `each_ref_fn`
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To allow users of the refs namespace to check if the reference backend
requires optimization, add a new field `optimize_required` field to
`struct ref_storage_be`. This field is of type `optimize_required_fn`
which is also introduced in this commit.
Modify the debug, files, packed and reftable backend to implement this
field. A following commit will expose this via 'git pack-refs' and 'git
refs optimize'.
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Message fix.
* pk/reflog-migrate-message-fix:
refs: add missing space in messages
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Our Bencher dashboards [1] have recently alerted us about a bunch of
performance regressions when writing references, specifically with the
reftable backend. There is a 3x regression when writing many refs with
preexisting refs in the reftable format, and a 10x regression when
migrating refs between backends in either of the formats.
Bisecting the issue lands us at 6ec4c0b45b (refs: don't store peeled
object IDs for invalid tags, 2025-10-23). The gist of the commit is that
we may end up storing peeled objects in both reftables and packed-refs
for corrupted tags, where the claimed tagged object type is different
than the actual tagged object type. This will then cause us to create
the `struct object *` with a wrong type, as well, and obviously nothing
good comes out of that.
The fix for this issue was to introduce a new flag to `peel_object()`
that causes us to verify the tagged object's type before writing it into
the refdb -- if the tag is corrupt, we skip writing the peeled value.
To verify whether the peeled value is correct we have to look up the
object type via the ODB and compare the actual type with the claimed
type, and that additional object lookup is costly.
This also explains why we see the regression only when writing refs with
the reftable backend, but we see the regression with both backends when
migrating refs:
- The reftable backend knows to store peeled values in the new table
immediately, so it has to try and peel each ref it's about to write
to the transaction. So the performance regression is visible for all
writes.
- The files backend only stores peeled values when writing the
packed-refs file, so it wouldn't hit the performance regression for
normal writes. But on ref migrations we know to write all new values
into the packed-refs file immediately, and that's why we see the
regression for both backends there.
Taking a step back though reveals an oddity in the new verification
logic: we not only verify the _tagged_ object's type, but we also verify
the type of the tag itself. But this isn't really needed, as we wouldn't
hit the bug in such a case anyway, as we only hit the issue with corrupt
tags claiming an invalid type for the tagged object.
The consequence of this is that we now started to look up the target
object of every single reference we're about to write, regardless of
whether it even is a tag or not. And that is of course quite costly.
Fix the issue by only verifying the type of the tagged objects. This
means that we of course still have a performance hit for actual tags.
But this only happens for writes anyway, and I'd claim it's preferable
to not store corrupted data in the refdb than to be fast here. Rename
the flag accordingly to clarify that we only verify the tagged object's
type.
This fix brings performance back to previous levels:
Benchmark 1: baseline
Time (mean ± σ): 46.0 ms ± 0.4 ms [User: 40.0 ms, System: 5.7 ms]
Range (min … max): 45.0 ms … 47.1 ms 54 runs
Benchmark 2: regression
Time (mean ± σ): 140.2 ms ± 1.3 ms [User: 77.5 ms, System: 60.5 ms]
Range (min … max): 138.0 ms … 142.7 ms 20 runs
Benchmark 3: fix
Time (mean ± σ): 46.2 ms ± 0.4 ms [User: 40.2 ms, System: 5.7 ms]
Range (min … max): 45.0 ms … 47.3 ms 55 runs
Summary
update-ref: baseline
1.00 ± 0.01 times faster than fix
3.05 ± 0.04 times faster than regression
[1]: https://bencher.dev/perf/git/plots
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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