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344 Commits

Author SHA1 Message Date
Junio C Hamano 7e44d8055c Merge branch 'mr/packed-ref-store-fix' into maint
Crash fix for a corner case where an error codepath tried to unlock
what it did not acquire lock on.

* mr/packed-ref-store-fix:
  files_initial_transaction_commit(): only unlock if locked
2018-03-22 14:24:10 -07:00
Mathias Rav 81fcb698e0 files_initial_transaction_commit(): only unlock if locked
Running git clone --single-branch --mirror -b TAGNAME previously
triggered the following error message:

	fatal: multiple updates for ref 'refs/tags/TAGNAME' not allowed.

This error condition is handled in files_initial_transaction_commit().

42c7f7ff9 ("commit_packed_refs(): remove call to `packed_refs_unlock()`", 2017-06-23)
introduced incorrect unlocking in the error path of this function,
which changes the error message to

	fatal: BUG: packed_refs_unlock() called when not locked

Move the call to packed_refs_unlock() above the "cleanup:" label
since the unlocking should only be done in the last error path.

Signed-off-by: Mathias Rav <m@git.strova.dk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-01-19 14:16:56 -08:00
Junio C Hamano 02abc6be8e Merge branch 'mh/avoid-rewriting-packed-refs' into maint
Recent update to the refs infrastructure implementation started
rewriting packed-refs file more often than before; this has been
optimized again for most trivial cases.

* mh/avoid-rewriting-packed-refs:
  files-backend: don't rewrite the `packed-refs` file unnecessarily
  t1409: check that `packed-refs` is not rewritten unnecessarily
2017-12-06 09:08:50 -08:00
Junio C Hamano a97222978a Merge branch 'mh/tidy-ref-update-flags'
Code clean-up in refs API implementation.

* mh/tidy-ref-update-flags:
  refs: update some more docs to use "oid" rather than "sha1"
  write_packed_entry(): take `object_id` arguments
  refs: rename constant `REF_ISPRUNING` to `REF_IS_PRUNING`
  refs: rename constant `REF_NODEREF` to `REF_NO_DEREF`
  refs: tidy up and adjust visibility of the `ref_update` flags
  ref_transaction_add_update(): remove a check
  ref_transaction_update(): die on disallowed flags
  prune_ref(): call `ref_transaction_add_update()` directly
  files_transaction_prepare(): don't leak flags to packed transaction
2017-11-15 12:14:29 +09:00
Junio C Hamano ffb0b5762e Merge branch 'mh/avoid-rewriting-packed-refs'
Recent update to the refs infrastructure implementation started
rewriting packed-refs file more often than before; this has been
optimized again for most trivial cases.

* mh/avoid-rewriting-packed-refs:
  files-backend: don't rewrite the `packed-refs` file unnecessarily
  t1409: check that `packed-refs` is not rewritten unnecessarily
2017-11-15 12:14:27 +09:00
Junio C Hamano e7e456f500 Merge branch 'bc/object-id'
Conversion from uchar[20] to struct object_id continues.

* bc/object-id: (25 commits)
  refs/files-backend: convert static functions to object_id
  refs: convert read_raw_ref backends to struct object_id
  refs: convert peel_object to struct object_id
  refs: convert resolve_ref_unsafe to struct object_id
  worktree: convert struct worktree to object_id
  refs: convert resolve_gitlink_ref to struct object_id
  Convert remaining callers of resolve_gitlink_ref to object_id
  sha1_file: convert index_path and index_fd to struct object_id
  refs: convert reflog_expire parameter to struct object_id
  refs: convert read_ref_at to struct object_id
  refs: convert peel_ref to struct object_id
  builtin/pack-objects: convert to struct object_id
  pack-bitmap: convert traverse_bitmap_commit_list to object_id
  refs: convert dwim_log to struct object_id
  builtin/reflog: convert remaining unsigned char uses to object_id
  refs: convert dwim_ref and expand_ref to struct object_id
  refs: convert read_ref and read_ref_full to object_id
  refs: convert resolve_refdup and refs_resolve_refdup to struct object_id
  Convert check_connected to use struct object_id
  refs: update ref transactions to use struct object_id
  ...
2017-11-06 14:24:27 +09:00
Michael Haggerty 78fb457968 refs: update some more docs to use "oid" rather than "sha1"
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:08 +09:00
Michael Haggerty 4170188262 write_packed_entry(): take `object_id` arguments
Change `write_packed_entry()` to take `struct object_id *` rather than
`unsigned char *` arguments.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:08 +09:00
Michael Haggerty acedcde76d refs: rename constant `REF_ISPRUNING` to `REF_IS_PRUNING`
Underscores are cheap, and help readability.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:08 +09:00
Michael Haggerty 91774afcc3 refs: rename constant `REF_NODEREF` to `REF_NO_DEREF`
Even after working with this code for years, I still see this constant
name as "ref node ref". Rename it to make it's meaning clearer.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:08 +09:00
Michael Haggerty 5ac95fee3d refs: tidy up and adjust visibility of the `ref_update` flags
The constants used for `ref_update::flags` were rather disorganized:

* The definitions in `refs.h` were not close to the functions that
  used them.

* Maybe constants were defined in `refs-internal.h`, making them
  visible to the whole refs module, when in fact they only made sense
  for the files backend.

* Their documentation wasn't very consistent and partly still referred
  to sha1s rather than oids.

* The numerical values followed no rational scheme

Fix all of these problems. The main functional improvement is that
some constants' visibility is now limited to `files-backend.c`.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:07 +09:00
Michael Haggerty 62c72d1fd0 ref_transaction_add_update(): remove a check
We want to make `REF_ISPRUNING` internal to the files backend. For
this to be possible, `ref_transaction_add_update()` mustn't know about
it. So move the check that `REF_ISPRUNING` is only used with
`REF_NODEREF` from this function to `files_transaction_prepare()`.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:07 +09:00
Michael Haggerty b00f3cfa92 prune_ref(): call `ref_transaction_add_update()` directly
`prune_ref()` needs to use the `REF_ISPRUNING` flag, but we want to
make that flag private to the files backend. So instead of calling
`ref_transaction_delete()`, which is a public function and therefore
shouldn't allow the `REF_ISPRUNING` flag, change `prune_ref()` to call
`ref_transaction_add_update()`, which is private to the refs
module. (Note that we don't need any of the other services provided by
`ref_transaction_delete()`.)

This allows us to change `ref_transaction_update()` to reject the
`REF_ISPRUNING` flag. Do so by adjusting
`REF_TRANSACTION_UPDATE_ALLOWED_FLAGS`. Also add parentheses to its
definition to avoid potential future mishaps.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:07 +09:00
Michael Haggerty b0ca411051 files_transaction_prepare(): don't leak flags to packed transaction
The files backend uses `ref_update::flags` for several internal flags.
But those flags have no meaning to the packed backend. So when adding
updates for the packed-refs transaction, only use flags that make
sense to the packed backend.

`REF_NODEREF` is part of the public interface, and it's logically what
we want, so include it. In fact it is actually ignored by the packed
backend (which doesn't support symbolic references), but that's its
own business.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06 10:31:07 +09:00
Michael Haggerty 7c6bd25c7d files-backend: don't rewrite the `packed-refs` file unnecessarily
Even when we are deleting references, we needn't overwrite the
`packed-refs` file if the references that we are deleting only exist
as loose references. Implement this optimization as follows:

* Add a function `is_packed_transaction_needed()`, which checks
  whether a given packed-refs transaction actually needs to be carried
  out (i.e., it returns false if the transaction obviously wouldn't
  have any effect). This function must be called while holding the
  `packed-refs` lock to avoid races.

* Change `files_transaction_prepare()` to check whether the
  packed-refs transaction is actually needed. If not, squelch it, but
  continue holding the `packed-refs` lock until the end of the
  transaction to avoid races.

This fixes a mild regression caused by dc39e09942 (files_ref_store:
use a transaction to update packed refs, 2017-09-08). Before that
commit, unnecessary rewrites of `packed-refs` were suppressed by
`repack_without_refs()`. But the transaction-based writing introduced
by that commit didn't perform that optimization.

Note that the pre-dc39e09942 code still had to *read* the whole
`packed-refs` file to determine that the rewrite could be skipped, so
the performance for the cases that the write could be elided was
`O(N)` in the number of packed references both before and after
dc39e09942. But after that commit the constant factor increased.

This commit reimplements the optimization of eliding unnecessary
`packed-refs` rewrites. That, plus the fact that since
cfa2e29c34 (packed_ref_store: get rid of the `ref_cache` entirely,
2017-03-17) we don't necessarily have to read the whole `packed-refs`
file at all, means that deletes of one or a few loose references can
now be done with `O(n lg N)` effort, where `n` is the number of loose
references being deleted and `N` is the total number of packed
references.

This commit fixes two tests in t1409.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-30 09:45:15 +09:00
Michael Haggerty ff08e56cde Merge branch 'bc/object-id' into base 2017-10-28 09:27:15 +02:00
Junio C Hamano 4e40fb302e Merge branch 'mh/ref-locking-fix'
Transactions to update multiple references that involves a deletion
was quite broken in an error codepath and did not abort everything
correctly.

* mh/ref-locking-fix:
  files_transaction_prepare(): fix handling of ref lock failure
  t1404: add a bunch of tests of D/F conflicts
2017-10-26 12:29:23 +09:00
Michael Haggerty da5267f1b6 files_transaction_prepare(): fix handling of ref lock failure
Since dc39e09942 (files_ref_store: use a transaction to update packed
refs, 2017-09-08), failure to lock a reference has been handled
incorrectly by `files_transaction_prepare()`. If
`lock_ref_for_update()` fails in the lock-acquisition loop of that
function, it sets `ret` then breaks out of that loop. Prior to
dc39e09942, that was OK, because the only thing following the loop was
the cleanup code. But dc39e09942 added another blurb of code between
the loop and the cleanup. That blurb sometimes resets `ret` to zero,
making the cleanup code think that the locking was successful.

Specifically, whenever

* One or more reference deletions have been processed successfully in
  the lock-acquisition loop. (Processing the first such reference
  causes a packed-ref transaction to be initialized.)

* Then `lock_ref_for_update()` fails for a subsequent reference. Such
  a failure can happen for a number of reasons, such as the old SHA-1
  not being correct, lock contention, etc. This causes a `break` out
  of the lock-acquisition loop.

* The `packed-refs` lock is acquired successfully and
  `ref_transaction_prepare()` succeeds for the packed-ref transaction.
  This has the effect of resetting `ret` back to 0, and making the
  cleanup code think that lock acquisition was successful.

In that case, any reference updates that were processed prior to
breaking out of the loop would be carried out (loose and packed), but
the reference that couldn't be locked and any subsequent references
would silently be ignored.

This can easily cause data loss if, for example, the user was trying
to push a new name for an existing branch while deleting the old name.
After the push, the branch could be left unreachable, and could even
subsequently be garbage-collected.

This problem was noticed in the context of deleting one reference and
creating another in a single transaction, when the two references D/F
conflict with each other, like

    git update-ref --stdin <<EOF
    delete refs/foo
    create refs/foo/bar HEAD
    EOF

This triggers the above bug because the deletion is processed
successfully for `refs/foo`, then the D/F conflict causes
`lock_ref_for_update()` to fail when `refs/foo/bar` is processed. In
this case the transaction *should* fail, but instead it causes
`refs/foo` to be deleted without creating `refs/foo`. This could
easily result in data loss.

The fix is simple: instead of just breaking out of the loop, jump
directly to the cleanup code. This fixes some tests in t1404 that were
added in the previous commit.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-25 15:08:26 +09:00
brian m. carlson 4f01e5080c refs/files-backend: convert static functions to object_id
Convert several static functions to take pointers to struct object_id.
Change the relevant parameters to write_packed_entry to be const, as we
don't modify them.  Rename lock_ref_sha1_basic to lock_ref_oid_basic to
reflect its new argument.  Update the docstring for verify lock to
account for the new parameter name, and note additionally that the
old_oid may be NULL.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:52 +09:00
brian m. carlson 99afe91a6c refs: convert read_raw_ref backends to struct object_id
Convert the unsigned char * parameter to struct object_id * for
files_read_raw_ref and packed_read_raw_ref.  Update the documentation.
Switch from using get_sha1_hex and a hard-coded 40 to using
parse_oid_hex.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:52 +09:00
brian m. carlson ac2ed0d7d5 refs: convert peel_object to struct object_id
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:52 +09:00
brian m. carlson 49e61479be refs: convert resolve_ref_unsafe to struct object_id
Convert resolve_ref_unsafe to take a pointer to struct object_id by
converting one remaining caller to use struct object_id, removing the
temporary NULL pointer check in expand_ref, converting the declaration
and definition, and applying the following semantic patch:

@@
expression E1, E2, E3, E4;
@@
- resolve_ref_unsafe(E1, E2, E3.hash, E4)
+ resolve_ref_unsafe(E1, E2, &E3, E4)

@@
expression E1, E2, E3, E4;
@@
- resolve_ref_unsafe(E1, E2, E3->hash, E4)
+ resolve_ref_unsafe(E1, E2, E3, E4)

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:51 +09:00
brian m. carlson 0155f710b8 refs: convert reflog_expire parameter to struct object_id
reflog_expire already used struct object_id internally, but it did not
take it as a parameter.  Adjust the parameter (and the callers) to pass
a pointer to struct object_id instead of a pointer to unsigned char.
Remove the temporary inserted earlier as it is no longer required.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:51 +09:00
brian m. carlson 34c290a6fc refs: convert read_ref and read_ref_full to object_id
All but two of the call sites already have parameters using the hash
parameter of struct object_id, so convert them to take a pointer to the
struct directly.  Also convert refs_read_refs_full, the underlying
implementation.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:50 +09:00
brian m. carlson 89f3bbdd3b refs: update ref transactions to use struct object_id
Update the ref transaction code to use struct object_id.  Remove one
NULL pointer check which was previously inserted around a dereference;
since we now pass a pointer to struct object_id directly through, the
code we're calling handles this for us.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:50 +09:00
brian m. carlson 2616a5e508 refs: convert delete_ref and refs_delete_ref to struct object_id
Convert delete_ref and refs_delete_ref to take a pointer to struct
object_id.  Update the documentation accordingly, including referring to
null_oid in lowercase, as it is not a #define constant.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:50 +09:00
brian m. carlson 49e9958869 refs/files-backend: convert struct ref_to_prune to object_id
Change the member of this struct to be a struct object_id.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16 11:05:50 +09:00
Junio C Hamano e46ebc2754 Merge branch 'rs/cleanup-strbuf-users'
Code clean-up.

* rs/cleanup-strbuf-users:
  graph: use strbuf_addchars() to add spaces
  use strbuf_addstr() for adding strings to strbufs
  path: use strbuf_add_real_path()
2017-10-05 13:48:19 +09:00
Junio C Hamano efe9d6ce33 Merge branch 'rs/resolve-ref-optional-result'
Code clean-up.

* rs/resolve-ref-optional-result:
  refs: pass NULL to resolve_refdup() if hash is not needed
  refs: pass NULL to refs_resolve_refdup() if hash is not needed
2017-10-05 13:48:19 +09:00
Junio C Hamano 1a2e1a76ec Merge branch 'mh/mmap-packed-refs'
Operations that do not touch (majority of) packed refs have been
optimized by making accesses to packed-refs file lazy; we no longer
pre-parse everything, and an access to a single ref in the
packed-refs does not touch majority of irrelevant refs, either.

* mh/mmap-packed-refs: (21 commits)
  packed-backend.c: rename a bunch of things and update comments
  mmapped_ref_iterator: inline into `packed_ref_iterator`
  ref_cache: remove support for storing peeled values
  packed_ref_store: get rid of the `ref_cache` entirely
  ref_store: implement `refs_peel_ref()` generically
  packed_read_raw_ref(): read the reference from the mmapped buffer
  packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`
  read_packed_refs(): ensure that references are ordered when read
  packed_ref_cache: keep the `packed-refs` file mmapped if possible
  packed-backend.c: reorder some definitions
  mmapped_ref_iterator_advance(): no peeled value for broken refs
  mmapped_ref_iterator: add iterator over a packed-refs file
  packed_ref_cache: remember the file-wide peeling state
  read_packed_refs(): read references with minimal copying
  read_packed_refs(): make parsing of the header line more robust
  read_packed_refs(): only check for a header at the top of the file
  read_packed_refs(): use mmap to read the `packed-refs` file
  die_unterminated_line(), die_invalid_line(): new functions
  packed_ref_cache: add a backlink to the associated `packed_ref_store`
  prefix_ref_iterator: break when we leave the prefix
  ...
2017-10-03 15:42:50 +09:00
Junio C Hamano cb1083ca23 Merge branch 'jk/read-in-full'
Code clean-up to prevent future mistakes by copying and pasting
code that checks the result of read_in_full() function.

* jk/read-in-full:
  worktree: check the result of read_in_full()
  worktree: use xsize_t to access file size
  distinguish error versus short read from read_in_full()
  avoid looking at errno for short read_in_full() returns
  prefer "!=" when checking read_in_full() result
  notes-merge: drop dead zero-write code
  files-backend: prefer "0" for write_in_full() error check
2017-10-03 15:42:49 +09:00
Junio C Hamano 3b48045c6c Merge branch 'sd/branch-copy'
"git branch" learned "-c/-C" to create a new branch by copying an
existing one.

* sd/branch-copy:
  branch: fix "copy" to never touch HEAD
  branch: add a --copy (-c) option to go with --move (-m)
  branch: add test for -m renaming multiple config sections
  config: create a function to format section headers
2017-10-03 15:42:48 +09:00
René Scharfe 72d4a9a721 use strbuf_addstr() for adding strings to strbufs
Use strbuf_addstr() instead of strbuf_addf() for adding strings.  That's
simpler and makes the intent clearer.

Patch generated by Coccinelle and contrib/coccinelle/strbuf.cocci;
adjusted indentation in refs/packed-backend.c manually.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-02 13:13:46 +09:00
René Scharfe 872ccb2c69 refs: pass NULL to refs_resolve_refdup() if hash is not needed
This gets us rid of a write-only variable.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-01 17:26:58 +09:00
Junio C Hamano 73ecdc606e Merge branch 'rs/resolve-ref-optional-result'
Code clean-up.

* rs/resolve-ref-optional-result:
  refs: pass NULL to resolve_ref_unsafe() if hash is not needed
  refs: pass NULL to refs_resolve_ref_unsafe() if hash is not needed
  refs: make sha1 output parameter of refs_resolve_ref_unsafe() optional
2017-09-28 14:47:56 +09:00
Jeff King 88780c37b3 files-backend: prefer "0" for write_in_full() error check
Commit 06f46f237a (avoid "write_in_full(fd, buf, len) !=
len" pattern, 2017-09-13) converted this callsite from:

  write_in_full(...) != 1

to

  write_in_full(...) < 0

But during the conflict resolution in c50424a6f0 (Merge
branch 'jk/write-in-full-fix', 2017-09-25), this morphed
into

  write_in_full(...) < 1

This behaves as we want, but we prefer to avoid modeling the
"less than length" error-check which can be subtly buggy, as
shown in efacf609c8 (config: avoid "write_in_full(fd, buf,
len) < len" pattern, 2017-09-13).

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-26 12:54:43 +09:00
Michael Haggerty cff28ca94c packed-backend.c: rename a bunch of things and update comments
We've made huge changes to this file, and some of the old names and
comments are no longer very fitting. So rename a bunch of things:

* `struct packed_ref_cache` → `struct snapshot`
* `acquire_packed_ref_cache()` → `acquire_snapshot()`
* `release_packed_ref_buffer()` → `clear_snapshot_buffer()`
* `release_packed_ref_cache()` → `release_snapshot()`
* `clear_packed_ref_cache()` → `clear_snapshot()`
* `struct packed_ref_entry` → `struct snapshot_record`
* `cmp_packed_ref_entries()` → `cmp_packed_ref_records()`
* `cmp_entry_to_refname()` → `cmp_record_to_refname()`
* `sort_packed_refs()` → `sort_snapshot()`
* `read_packed_refs()` → `create_snapshot()`
* `validate_packed_ref_cache()` → `validate_snapshot()`
* `get_packed_ref_cache()` → `get_snapshot()`
* Renamed local variables and struct members accordingly.

Also update a bunch of comments to reflect the renaming and the
accumulated changes that the code has undergone.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:46 +09:00
Michael Haggerty 523ee2d785 mmapped_ref_iterator: inline into `packed_ref_iterator`
Since `packed_ref_iterator` is now delegating to
`mmapped_ref_iterator` rather than `cache_ref_iterator` to do the
heavy lifting, there is no need to keep the two iterators separate. So
"inline" `mmapped_ref_iterator` into `packed_ref_iterator`. This
removes a bunch of boilerplate.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:46 +09:00
Michael Haggerty a6e19bcdad ref_cache: remove support for storing peeled values
Now that the `packed-refs` backend doesn't use `ref_cache`, there is
nobody left who might want to store peeled values of references in
`ref_cache`. So remove that feature.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:46 +09:00
Michael Haggerty 9dd389f3d8 packed_ref_store: get rid of the `ref_cache` entirely
Now that everything has been changed to read what it needs directly
out of the `packed-refs` file, `packed_ref_store` doesn't need to
maintain a `ref_cache` at all. So get rid of it.

First of all, this will save a lot of memory and lots of little
allocations. Instead of needing to store complicated parsed data
structures in memory, we just mmap the file (potentially sharing
memory with other processes) and parse only what we need.

Moreover, since the mmapped access to the file reads only the parts of
the file that it needs, this might save reading all of the data from
disk at all (at least if the file starts out sorted).

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:46 +09:00
Michael Haggerty ba1c052fa6 ref_store: implement `refs_peel_ref()` generically
We're about to stop storing packed refs in a `ref_cache`. That means
that the only way we have left to optimize `peel_ref()` is by checking
whether the reference being peeled is the one currently being iterated
over (in `current_ref_iter`), and if so, using `ref_iterator_peel()`.
But this can be done generically; it doesn't have to be implemented
per-backend.

So implement `refs_peel_ref()` in `refs.c` and remove the `peel_ref()`
method from the refs API.

This removes the last callers of a couple of functions, so delete
them. More cleanup to come...

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:46 +09:00
Michael Haggerty f3987ab36d packed_read_raw_ref(): read the reference from the mmapped buffer
Instead of reading the reference from the `ref_cache`, read it
directly from the mmapped buffer.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:45 +09:00
Michael Haggerty d1cf15516f packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`
Now that we have an efficient way to iterate, in order, over the
mmapped contents of the `packed-refs` file, we can use that directly
to implement reference iteration for the `packed_ref_store`, rather
than iterating over the `ref_cache`. This is the next step towards
getting rid of the `ref_cache` entirely.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:45 +09:00
Michael Haggerty 02b920f3f7 read_packed_refs(): ensure that references are ordered when read
It doesn't actually matter now, because the references are only
iterated over to fill the associated `ref_cache`, which itself puts
them in the correct order. But we want to get rid of the `ref_cache`,
so we want to be able to iterate directly over the `packed-refs`
buffer, and then the iteration will need to be ordered correctly.

In fact, we already write the `packed-refs` file sorted, but it is
possible that other Git clients don't get it right. So let's not
assume that a `packed-refs` file is sorted unless it is explicitly
declared to be so via a `sorted` trait in its header line.

If it is *not* declared to be sorted, then scan quickly through the
file to check. If it is found to be out of order, then sort the
records into a new memory-only copy. This checking and sorting is done
quickly, without parsing the full file contents. However, it needs a
little bit of care to avoid reading past the end of the buffer even if
the `packed-refs` file is corrupt.

Since *we* always write the file correctly sorted, include that trait
when we write or rewrite a `packed-refs` file. This means that the
scan described in the previous paragraph should only have to be done
for `packed-refs` files that were written by older versions of the Git
command-line client, or by other clients that haven't yet learned to
write the `sorted` trait.

If `packed-refs` was already sorted, then (if the system allows it) we
can use the mmapped file contents directly. But if the system doesn't
allow a file that is currently mmapped to be replaced using
`rename()`, then it would be bad for us to keep the file mmapped for
any longer than necessary. So, on such systems, always make a copy of
the file contents, either as part of the sorting process, or
afterwards.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-25 18:02:45 +09:00
Michael Haggerty 5b633610ec packed_ref_cache: keep the `packed-refs` file mmapped if possible
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>
2017-09-25 18:02:45 +09:00
Michael Haggerty 14b3c344ea packed-backend.c: reorder some definitions
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>
2017-09-25 18:02:45 +09:00
Michael Haggerty 81b9b5aea7 mmapped_ref_iterator_advance(): no peeled value for broken refs
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>
2017-09-25 18:02:45 +09:00
Michael Haggerty 9cfb3dc0d1 mmapped_ref_iterator: add iterator over a packed-refs file
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>
2017-09-25 18:02:45 +09:00
Michael Haggerty daa45408c1 packed_ref_cache: remember the file-wide peeling state
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>
2017-09-25 18:02:45 +09:00
Michael Haggerty 6a9bc4034a read_packed_refs(): read references with minimal copying
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>
2017-09-25 18:02:45 +09:00