Keep a copy of the `packed-refs` file contents in memory for as long
as a `packed_ref_cache` object is in use:
* If the system allows it, keep the `packed-refs` file mmapped.
* If not (either because the system doesn't support `mmap()` at all,
or because a file that is currently mmapped cannot be replaced via
`rename()`), then make a copy of the file's contents in
heap-allocated space, and keep that around instead.
We base the choice of behavior on a new build-time switch,
`MMAP_PREVENTS_DELETE`. By default, this switch is set for Windows
variants.
After this commit, `MMAP_NONE` and `MMAP_TEMPORARY` are still handled
identically. But the next commit will introduce a difference.
This whole change is still pointless, because we only read the
`packed-refs` file contents immediately after instantiating the
`packed_ref_cache`. But that will soon change.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
No code has been changed. This will make subsequent patches more
self-contained.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a reference is broken, suppress its peeled value.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a new `mmapped_ref_iterator`, which can iterate over the
references in an mmapped `packed-refs` file directly. Use this
iterator from `read_packed_refs()` to fill the packed refs cache.
Note that we are not yet willing to promise that the new iterator
generates its output in order. That doesn't matter for now, because
the packed refs cache doesn't care what order it is filled.
This change adds a lot of boilerplate without providing any obvious
benefits. The benefits will come soon, when we get rid of the
`ref_cache` for packed references altogether.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rather than store the peeling state (i.e., the one defined by traits
in the `packed-refs` file header line) in a local variable in
`read_packed_refs()`, store it permanently in `packed_ref_cache`. This
will be needed when we stop reading all packed refs at once.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Instead of copying data from the `packed-refs` file one line at time
and then processing it, process the data in place as much as possible.
Also, instead of processing one line per iteration of the main loop,
process a reference line plus its corresponding peeled line (if
present) together.
Note that this change slightly tightens up the parsing of the
`packed-refs` file. Previously, the parser would have accepted
multiple "peeled" lines for a single reference (ignoring all but the
last one). Now it would reject that.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The old code parsed the traits in the `packed-refs` header by looking
for the string " trait " (i.e., the name of the trait with a space on
either side) in the header line. This is fragile, because if any other
implementation of Git forgets to write the trailing space, the last
trait would silently be ignored (and the error might never be
noticed).
So instead, use `string_list_split_in_place()` to split the traits
into tokens then use `unsorted_string_list_has_string()` to look for
the tokens we are interested in. This means that we can read the
traits correctly even if the header line is missing a trailing
space (or indeed, if it is missing the space after the colon, or if it
has multiple spaces somewhere).
However, older Git clients (and perhaps other Git implementations)
still require the surrounding spaces, so we still have to output the
header with a trailing space.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This tightens up the parsing a bit; previously, stray header-looking
lines would have been processed.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It's still done in a pretty stupid way, involving more data copying
than necessary. That will improve in future commits.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Extract some helper functions for reporting errors. While we're at it,
prevent them from spewing unlimited output to the terminal. These
functions will soon have more callers.
These functions accept the problematic line as a `(ptr, len)` pair
rather than a NUL-terminated string, and `die_invalid_line()` checks
for an EOL itself, because these calling conventions will be
convenient for future callers. (Efficiency is not a concern here
because these functions are only ever called if the `packed-refs` file
is corrupt.)
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
References are iterated over in order by refname, but reflogs are not.
Some consumers of reference iteration care about the difference. Teach
each `ref_iterator` to keep track of whether its output is ordered.
`overlay_ref_iterator` is one of the picky consumers. Add a sanity
check in `overlay_ref_iterator_begin()` to verify that its inputs are
ordered.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now the outside world interacts with the packed ref store only via the
generic refs API plus a few lock-related functions. This allows us to
delete some functions that are no longer used, thereby completing the
encapsulation of the packed ref store.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Implement `packed_delete_refs()` using a reference transaction. This
means that `files_delete_refs()` can use `refs_delete_refs()` instead
of `repack_without_refs()` to delete any packed references, decreasing
the coupling between the classes.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Implement the methods needed to support reference transactions for
the packed-refs backend. The new methods are not yet used.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The old code incremented the packed ref cache reference count when
acquiring the packed-refs lock, and decremented the count when
releasing the lock. This is unnecessary because:
* Another process cannot change the packed-refs file because it is
locked.
* When we ourselves change the packed-refs file, we do so by first
modifying the packed ref-cache, and then writing the data from the
ref-cache to disk. So the packed ref-cache remains fresh because any
changes that we plan to make to the file are made in the cache first
anyway.
So there is no reason for the cache to become stale.
Moreover, the extra reference count causes a problem if we
intentionally clear the packed refs cache, as we sometimes need to do
if we change the cache in anticipation of writing a change to disk,
but then the write to disk fails. In that case, `packed_refs_unlock()`
would have no easy way to find the cache whose reference count it
needs to decrement.
This whole issue will soon become moot due to upcoming changes that
avoid changing the in-memory cache as part of updating the packed-refs
on disk, but this change makes that transition easier.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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
...
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
