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2017-08-26Merge branch 'mh/ref-lock-entry'Libravatar Junio C Hamano2-2/+12
The code to acquire a lock on a reference (e.g. while accepting a push from a client) used to immediately fail when the reference is already locked---now it waits for a very short while and retries, which can make it succeed if the lock holder was holding it during a read-only operation. * mh/ref-lock-entry: refs: retry acquiring reference locks for 100ms
2017-08-23refs: retry acquiring reference locks for 100msLibravatar Michael Haggerty2-2/+12
The philosophy of reference locking has been, "if another process is changing a reference, then whatever I'm trying to do to it will probably fail anyway because my old-SHA-1 value is probably no longer current". But this argument falls down if the other process has locked the reference to do something that doesn't actually change the value of the reference, such as `pack-refs` or `reflog expire`. There actually *is* a decent chance that a planned reference update will still be able to go through after the other process has released the lock. So when trying to lock an individual reference (e.g., when creating "refs/heads/master.lock"), if it is already locked, then retry the lock acquisition for approximately 100 ms before giving up. This should eliminate some unnecessary lock conflicts without wasting a lot of time. Add a configuration setting, `core.filesRefLockTimeout`, to allow this setting to be tweaked. Note: the function `get_files_ref_lock_timeout_ms()` cannot be private to the files backend because it is also used by `write_pseudoref()` and `delete_pseudoref()`, which are defined in `refs.c` so that they can be used by other reference backends. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-08-22Merge branch 'mh/packed-ref-store'Libravatar Junio C Hamano4-564/+995
The "ref-store" code reorganization continues. * mh/packed-ref-store: (32 commits) files-backend: cheapen refname_available check when locking refs packed_ref_store: handle a packed-refs file that is a symlink read_packed_refs(): die if `packed-refs` contains bogus data t3210: add some tests of bogus packed-refs file contents repack_without_refs(): don't lock or unlock the packed refs commit_packed_refs(): remove call to `packed_refs_unlock()` clear_packed_ref_cache(): don't protest if the lock is held packed_refs_unlock(), packed_refs_is_locked(): new functions packed_refs_lock(): report errors via a `struct strbuf *err` packed_refs_lock(): function renamed from lock_packed_refs() commit_packed_refs(): use a staging file separate from the lockfile commit_packed_refs(): report errors rather than dying packed_ref_store: make class into a subclass of `ref_store` packed-backend: new module for handling packed references packed_read_raw_ref(): new function, replacing `resolve_packed_ref()` packed_ref_store: support iteration packed_peel_ref(): new function, extracted from `files_peel_ref()` repack_without_refs(): take a `packed_ref_store *` parameter get_packed_ref(): take a `packed_ref_store *` parameter rollback_packed_refs(): take a `packed_ref_store *` parameter ...
2017-08-17files-backend: cheapen refname_available check when locking refsLibravatar Michael Haggerty1-4/+4
When locking references in preparation for updating them, we need to check that none of the newly added references D/F conflict with existing references (e.g., we don't allow `refs/foo` to be added if `refs/foo/bar` already exists, or vice versa). Prior to 524a9fdb51 (refs_verify_refname_available(): use function in more places, 2017-04-16), conflicts with existing loose references were checked by looking directly in the filesystem, and then conflicts with existing packed references were checked by running `verify_refname_available_dir()` against the packed-refs cache. But that commit changed the final check to call `refs_verify_refname_available()` against the *whole* files ref-store, including both loose and packed references, with the following comment: > This means that those callsites now check for conflicts with all > references rather than just packed refs, but the performance cost > shouldn't be significant (and will be regained later). That comment turned out to be too sanguine. User s@kazlauskas.me reported that fetches involving a very large number of references in neighboring directories were slowed down by that change. The problem is that when fetching, each reference is updated individually, within its own reference transaction. This is done because some reference updates might succeed even though others fail. But every time a reference update transaction is finished, `clear_loose_ref_cache()` is called. So when it is time to update the next reference, part of the loose ref cache has to be repopulated for the `refs_verify_refname_available()` call. If the references are all in neighboring directories, then the cost of repopulating the reference cache increases with the number of references, resulting in O(N²) effort. The comment above also claims that the performance cost "will be regained later". The idea was that once the packed-refs were finished being split out into a separate ref-store, we could limit the `refs_verify_refname_available()` call to the packed references again. That is what we do now. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-07-27packed_ref_store: handle a packed-refs file that is a symlinkLibravatar Michael Haggerty1-6/+18
One of the tricks that `contrib/workdir/git-new-workdir` plays is to making `packed-refs` in the new workdir a symlink to the `packed-refs` file in the original repository. Before 42dfa7ecef ("commit_packed_refs(): use a staging file separate from the lockfile", 2017-06-23), a lockfile was used as the staging file, and because the `LOCK_NO_DEREF` was not used, the pointed-to file was locked and modified. But after that commit, the staging file was created using a tempfile, with the end result that rewriting the `packed-refs` file in the workdir overwrote the symlink rather than the original `packed-refs` file. Change `commit_packed_refs()` to use `get_locked_file_path()` to find the path of the file that it should overwrite. Since that path was properly resolved when the lockfile was created, this restores the pre-42dfa7ecef behavior. Also add a test case to document this use case and prevent a regression like this from recurring. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-07-03read_packed_refs(): die if `packed-refs` contains bogus dataLibravatar Michael Haggerty1-3/+7
The old code ignored any lines that it didn't understand, including unterminated lines. This is dangerous. Instead, `die()` if the `packed-refs` file contains any unterminated lines or lines that we don't know how to handle. This fixes the tests added in the last commit. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-07-03repack_without_refs(): don't lock or unlock the packed refsLibravatar Michael Haggerty2-40/+39
Change `repack_without_refs()` to expect the packed-refs lock to be held already, and not to release the lock before returning. Change the callers to deal with lock management. This change makes it possible for callers to hold the packed-refs lock for a longer span of time, a possibility that will eventually make it possible to fix some longstanding races. The only semantic change here is that `repack_without_refs()` used to forget to release the lock in the `if (!removed)` exit path. That omission is now fixed. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-26Merge branch 'mh/packed-ref-store-prep'Libravatar Junio C Hamano1-9/+23
Bugfix for a topic that is (only) in 'master'. * mh/packed-ref-store-prep: for_each_bisect_ref(): don't trim refnames lock_packed_refs(): fix cache validity check
2017-06-24Merge branch 'ab/free-and-null'Libravatar Junio C Hamano2-4/+2
A common pattern to free a piece of memory and assign NULL to the pointer that used to point at it has been replaced with a new FREE_AND_NULL() macro. * ab/free-and-null: *.[ch] refactoring: make use of the FREE_AND_NULL() macro coccinelle: make use of the "expression" FREE_AND_NULL() rule coccinelle: add a rule to make "expression" code use FREE_AND_NULL() coccinelle: make use of the "type" FREE_AND_NULL() rule coccinelle: add a rule to make "type" code use FREE_AND_NULL() git-compat-util: add a FREE_AND_NULL() wrapper around free(ptr); ptr = NULL
2017-06-24Merge branch 'bw/config-h'Libravatar Junio C Hamano1-0/+1
Fix configuration codepath to pay proper attention to commondir that is used in multi-worktree situation, and isolate config API into its own header file. * bw/config-h: config: don't implicitly use gitdir or commondir config: respect commondir setup: teach discover_git_directory to respect the commondir config: don't include config.h by default config: remove git_config_iter config: create config.h
2017-06-23commit_packed_refs(): remove call to `packed_refs_unlock()`Libravatar Michael Haggerty2-10/+10
Instead, change the callers of `commit_packed_refs()` to call `packed_refs_unlock()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23clear_packed_ref_cache(): don't protest if the lock is heldLibravatar Michael Haggerty1-2/+0
The existing callers already check that the lock isn't held just before calling `clear_packed_ref_cache()`, and in the near future we want to be able to call this function when the lock is held. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_refs_unlock(), packed_refs_is_locked(): new functionsLibravatar Michael Haggerty2-6/+28
Add two new public functions, `packed_refs_unlock()` and `packed_refs_is_locked()`, with which callers can manage and query the `packed-refs` lock externally. Call `packed_refs_unlock()` from `commit_packed_refs()` and `rollback_packed_refs()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_refs_lock(): report errors via a `struct strbuf *err`Libravatar Michael Haggerty3-13/+16
That way the callers don't have to come up with error messages themselves. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_refs_lock(): function renamed from lock_packed_refs()Libravatar Michael Haggerty3-8/+8
Rename `lock_packed_refs()` to `packed_refs_lock()` for consistency with how other methods are named. Also, it's about to get some companions. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23commit_packed_refs(): use a staging file separate from the lockfileLibravatar Michael Haggerty1-8/+32
We will want to be able to hold the lockfile for `packed-refs` even after we have activated the new values. So use a separate tempfile, `packed-refs.new`, as a place to stage the new contents of the `packed-refs` file. For now this is all done within `commit_packed_refs()`, but that will change shortly. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23commit_packed_refs(): report errors rather than dyingLibravatar Michael Haggerty3-36/+61
Report errors via a `struct strbuf *err` rather than by calling `die()`. To enable this goal, change `write_packed_entry()` to report errors via a return value and `errno` rather than dying. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_ref_store: make class into a subclass of `ref_store`Libravatar Michael Haggerty4-45/+227
Add the infrastructure to make `packed_ref_store` implement `ref_store`, at least formally (few of the methods are actually implemented yet). Change the functions in its interface to take `ref_store *` arguments. Change `files_ref_store` to store a pointer to `ref_store *` and to call functions via the virtual `ref_store` interface where possible. This also means that a few `packed_ref_store` functions can become static. This is a work in progress. Some more `ref_store` methods will soon be implemented (e.g., those having to do with reference transactions). But some of them will never be implemented (e.g., those having to do with symrefs or reflogs). Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed-backend: new module for handling packed referencesLibravatar Michael Haggerty4-639/+666
Now that the interface between `files_ref_store` and `packed_ref_store` is relatively narrow, move the latter into a new module, "refs/packed-backend.h" and "refs/packed-backend.c". It still doesn't quite implement the `ref_store` interface, but it will soon. This commit moves code around and adjusts its visibility, but doesn't change anything. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_read_raw_ref(): new function, replacing `resolve_packed_ref()`Libravatar Michael Haggerty1-19/+17
Add a new function, `packed_read_raw_ref()`, which is nearly a `read_raw_ref_fn`. Use it in place of `resolve_packed_ref()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_ref_store: support iterationLibravatar Michael Haggerty1-9/+110
Add the infrastructure to iterate over a `packed_ref_store`. It's a lot of boilerplate, but it's all part of a campaign to make `packed_ref_store` implement `ref_store`. In the future, this iterator will work much differently. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_peel_ref(): new function, extracted from `files_peel_ref()`Libravatar Michael Haggerty1-11/+15
This will later become a method of `packed_ref_store`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23repack_without_refs(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-10/+10
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23get_packed_ref(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-5/+7
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23rollback_packed_refs(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-8/+7
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23commit_packed_refs(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-9/+9
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23lock_packed_refs(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-9/+22
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23add_packed_ref(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-5/+5
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23get_packed_refs(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-5/+5
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23get_packed_ref_cache(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-14/+12
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23validate_packed_ref_cache(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-7/+6
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23clear_packed_ref_cache(): take a `packed_ref_store *` parameterLibravatar Michael Haggerty1-8/+8
It only cares about the packed-refs part of the reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_ref_store: move `packed_refs_lock` member hereLibravatar Michael Haggerty1-15/+16
Move the `packed_refs_lock` member from `files_ref_store` to `packed_ref_store`, and rename it to `lock` since it's now more obvious what it is locking. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_ref_store: move `packed_refs_path` hereLibravatar Michael Haggerty1-13/+12
Move `packed_refs_path` from `files_ref_store` to `packed_ref_store`, and rename it to `path` since its meaning is clear from its new context. Inline `files_packed_refs_path()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23packed_ref_store: new structLibravatar Michael Haggerty1-9/+33
Start extracting the packed-refs-related data structures into a new class, `packed_ref_store`. It doesn't yet implement `ref_store`, but it will. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-23add_packed_ref(): teach function to overwrite existing refsLibravatar Michael Haggerty1-22/+18
Teach `add_packed_ref()` to overwrite an existing entry if one already exists for the specified `refname`. This means that we can call it from `files_pack_refs()`, thereby reducing the amount that the latter function needs to know about the internals of packed-reference handling. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-16*.[ch] refactoring: make use of the FREE_AND_NULL() macroLibravatar Ævar Arnfjörð Bjarmason1-2/+1
Replace occurrences of `free(ptr); ptr = NULL` which weren't caught by the coccinelle rule. These fall into two categories: - free/NULL assignments one after the other which coccinelle all put on one line, which is functionally equivalent code, but very ugly. - manually spotted occurrences where the NULL assignment isn't right after the free() call. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-16coccinelle: make use of the "type" FREE_AND_NULL() ruleLibravatar Ævar Arnfjörð Bjarmason1-2/+1
Apply the result of the just-added coccinelle rule. This manually excludes a few occurrences, mostly things that resulted in many FREE_AND_NULL() on one line, that'll be manually fixed in a subsequent change. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-15config: don't include config.h by defaultLibravatar Brandon Williams1-0/+1
Stop including config.h by default in cache.h. Instead only include config.h in those files which require use of the config system. Signed-off-by: Brandon Williams <bmwill@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-12lock_packed_refs(): fix cache validity checkLibravatar Michael Haggerty1-9/+23
Commit 28ed9830b1 (get_packed_ref_cache(): assume "packed-refs" won't change while locked, 2017-05-22) assumes that the "packed-refs" file cannot change while we hold the lock. That assumption is justified *if* the lock has been held the whole time since the "packed-refs" file was last read. But in `lock_packed_refs()`, we ourselves lock the "packed-refs" file and then call `get_packed_ref_cache()` to ensure that the cache agrees with the file. The intent is to guard against the possibility that another process changed the "packed-refs" file the moment before we locked it. This check was defeated because `get_packed_ref_cache()` saw that the file was locked, and therefore didn't do the `stat_validity_check()` that we want. The mistake was compounded with a misleading comment in `lock_packed_refs()` claiming that it was doing the right thing. That comment came from an earlier draft of the mh/packed-ref-store-prep patch series when the commits were in a different order. So instead: * Extract a function `validate_packed_ref_cache()` that does the validity check independent of whether the lock is held. * Change `get_packed_ref_cache()` to call the new function, but only if the lock *isn't* held. * Change `lock_packed_refs()` to call the new function in any case before calling `get_packed_ref_cache()`. * Fix the comment in `lock_packed_refs()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-24cache_ref_iterator_begin(): avoid priming unneeded directoriesLibravatar Michael Haggerty1-10/+85
When iterating over references, reference priming is used to make sure that loose references are read into the ref-cache before packed references, to avoid races. It used to be that the prefix passed to reference iterators almost always ended in `/`, for example `refs/heads/`. In that case, the priming code would read all loose references under `find_containing_dir("refs/heads/")`, which is "refs/heads/". That's just what we want. But now that `ref-filter` knows how to pass refname prefixes to `for_each_fullref_in()`, the prefix might come from user input; for example, git for-each-ref refs/heads Since the argument doesn't include a trailing slash, the reference iteration code would prime all of the loose references under `find_containing_dir("refs/heads")`, which is "refs/". Thus we would unnecessarily read tags, remote-tracking references, etc., when the user is only interested in branches. It is a bit awkward to get around this problem. We can't just append a slash to the argument, because we don't know ab initio whether an argument like `refs/tags/release` corresponds to a single tag or to a directory containing tags. Moreover, until now a `prefix_ref_iterator` was used to make the final decision about which references fall within the prefix (the `cache_ref_iterator` only did a rough cut). This is also inefficient, because the `prefix_ref_iterator` can't know, for example, that while you are in a subdirectory that is completely within the prefix, you don't have to do the prefix check. So: * Move the responsibility for doing the prefix check directly to `cache_ref_iterator`. This means that `cache_ref_iterator_begin()` never has to wrap its return value in a `prefix_ref_iterator`. * Teach `cache_ref_iterator_begin()` (and `prime_ref_dir()`) to be stricter about what they iterate over and what directories they prime. * Teach `cache_ref_iterator` to keep track of whether the current `cache_ref_iterator_level` is fully within the prefix. If so, skip the prefix checks entirely. The main benefit of these optimizations is for loose references, since packed references are always read all at once. Note that after this change, `prefix_ref_iterator` is only ever used for its trimming feature and not for its "prefix" feature. But I'm not ripping out the latter yet, because it might be useful for another patch series that I'm working on. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23create_ref_entry(): remove `check_name` optionLibravatar Michael Haggerty3-11/+10
Only one caller was using it, so move the check to that caller. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23refs_ref_iterator_begin(): handle `GIT_REF_PARANOIA`Libravatar Michael Haggerty1-7/+4
Instead of handling `GIT_REF_PARANOIA` in `files_ref_iterator_begin()`, handle it in `refs_ref_iterator_begin()`, where it will cover all reference stores. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23read_packed_refs(): report unexpected fopen() failuresLibravatar Michael Haggerty1-2/+12
The old code ignored any errors encountered when trying to fopen the "packed-refs" file, treating all such failures as if the file didn't exist. But it could be that there is some other error opening the file (e.g., permissions problems), and we don't want to silently ignore such problems. So report any failures that are not due to ENOENT. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23read_packed_refs(): do more of the work of reading packed refsLibravatar Michael Haggerty2-17/+26
Teach `read_packed_refs()` to also * Allocate and initialize the new `packed_ref_cache` * Open and close the `packed-refs` file * Update the `validity` field of the new object This decreases the coupling between `packed_refs_cache` and `files_ref_store` by a little bit. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23get_packed_ref_cache(): assume "packed-refs" won't change while lockedLibravatar Michael Haggerty1-5/+11
If we've got the "packed-refs" file locked, then it can't change; there's no need to keep calling `stat_validity_check()` on it. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23should_pack_ref(): new function, extracted from `files_pack_refs()`Libravatar Michael Haggerty1-14/+28
Extract a function for deciding whether a reference should be packed. It is a self-contained bit of logic, so splitting it out improves readability. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_update_reject_duplicates(): expose function to whole refs moduleLibravatar Michael Haggerty2-17/+8
It will soon have some other users. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_transaction_prepare(): new optional step for reference updatesLibravatar Michael Haggerty2-23/+85
In the future, compound reference stores will sometimes need to modify references in two different reference stores at the same time, meaning that a single logical reference transaction might have to be implemented as two internal sub-transactions. They won't want to call `ref_transaction_commit()` for the two sub-transactions one after the other, because that wouldn't be atomic (the first commit could succeed and the second one fail). Instead, they will want to prepare both sub-transactions (i.e., obtain any necessary locks and do any pre-checks), and only if both prepare steps succeed, then commit both sub-transactions. Start preparing for that day by adding a new, optional `ref_transaction_prepare()` step to the reference transaction sequence, which obtains the locks and does any prechecks, reporting any errors that occur. Also add a `ref_transaction_abort()` function that can be used to abort a sub-transaction even if it has already been prepared. That is on the side of the public-facing API. On the side of the `ref_store` VTABLE, get rid of `transaction_commit` and instead add methods `transaction_prepare`, `transaction_finish`, and `transaction_abort`. A `ref_transaction_commit()` now basically calls methods `transaction_prepare` then `transaction_finish`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_transaction_commit(): check for valid `transaction->state`Libravatar Michael Haggerty1-3/+0
Move the check that `transaction->state` is valid from `files_transaction_commit()` to `ref_transaction_commit()`, where other future reference backends can benefit from it as well. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>