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2017-11-15Merge branch 'mh/tidy-ref-update-flags'Libravatar Junio C Hamano4-108/+127
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
2017-11-15Merge branch 'mh/avoid-rewriting-packed-refs'Libravatar Junio C Hamano3-1/+120
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
2017-11-06Merge branch 'bc/object-id'Libravatar Junio C Hamano4-74/+72
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 ...
2017-11-06refs: update some more docs to use "oid" rather than "sha1"Libravatar Michael Haggerty4-22/+21
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06write_packed_entry(): take `object_id` argumentsLibravatar Michael Haggerty1-8/+8
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>
2017-11-06refs: rename constant `REF_ISPRUNING` to `REF_IS_PRUNING`Libravatar Michael Haggerty1-9/+9
Underscores are cheap, and help readability. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-06refs: rename constant `REF_NODEREF` to `REF_NO_DEREF`Libravatar Michael Haggerty2-22/+22
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>
2017-11-06refs: tidy up and adjust visibility of the `ref_update` flagsLibravatar Michael Haggerty2-52/+60
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>
2017-11-06ref_transaction_add_update(): remove a checkLibravatar Michael Haggerty1-1/+6
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>
2017-11-06prune_ref(): call `ref_transaction_add_update()` directlyLibravatar Michael Haggerty1-9/+16
`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>
2017-11-06files_transaction_prepare(): don't leak flags to packed transactionLibravatar Michael Haggerty1-2/+2
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>
2017-10-30files-backend: don't rewrite the `packed-refs` file unnecessarilyLibravatar Michael Haggerty3-1/+120
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>
2017-10-28Merge branch 'bc/object-id' into baseLibravatar Michael Haggerty4-74/+72
2017-10-26Merge branch 'mh/ref-locking-fix'Libravatar Junio C Hamano1-1/+1
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
2017-10-25files_transaction_prepare(): fix handling of ref lock failureLibravatar Michael Haggerty1-1/+1
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>
2017-10-16refs/files-backend: convert static functions to object_idLibravatar brian m. carlson1-28/+28
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>
2017-10-16refs: convert read_raw_ref backends to struct object_idLibravatar brian m. carlson3-13/+14
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>
2017-10-16refs: convert peel_object to struct object_idLibravatar brian m. carlson3-6/+6
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-16refs: convert resolve_ref_unsafe to struct object_idLibravatar brian m. carlson1-4/+4
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>
2017-10-16refs: convert reflog_expire parameter to struct object_idLibravatar brian m. carlson3-8/+5
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>
2017-10-16refs: convert read_ref and read_ref_full to object_idLibravatar brian m. carlson1-5/+5
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>
2017-10-16refs: update ref transactions to use struct object_idLibravatar brian m. carlson2-8/+8
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>
2017-10-16refs: convert delete_ref and refs_delete_ref to struct object_idLibravatar brian m. carlson1-1/+1
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>
2017-10-16refs/files-backend: convert struct ref_to_prune to object_idLibravatar brian m. carlson1-3/+3
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>
2017-10-05Merge branch 'rs/cleanup-strbuf-users'Libravatar Junio C Hamano1-2/+2
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()
2017-10-05Merge branch 'rs/resolve-ref-optional-result'Libravatar Junio C Hamano1-2/+1
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
2017-10-03Merge branch 'mh/mmap-packed-refs'Libravatar Junio C Hamano6-368/+818
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 ...
2017-10-03Merge branch 'jk/read-in-full'Libravatar Junio C Hamano1-1/+1
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
2017-10-03Merge branch 'sd/branch-copy'Libravatar Junio C Hamano3-8/+50
"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
2017-10-02use strbuf_addstr() for adding strings to strbufsLibravatar René Scharfe1-2/+2
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>
2017-10-01refs: pass NULL to refs_resolve_refdup() if hash is not neededLibravatar René Scharfe1-2/+1
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>
2017-09-28Merge branch 'rs/resolve-ref-optional-result'Libravatar Junio C Hamano1-2/+1
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
2017-09-26files-backend: prefer "0" for write_in_full() error checkLibravatar Jeff King1-1/+1
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>
2017-09-25packed-backend.c: rename a bunch of things and update commentsLibravatar Michael Haggerty1-190/+232
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>
2017-09-25mmapped_ref_iterator: inline into `packed_ref_iterator`Libravatar Michael Haggerty1-170/+114
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>
2017-09-25ref_cache: remove support for storing peeled valuesLibravatar Michael Haggerty3-72/+11
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>
2017-09-25packed_ref_store: get rid of the `ref_cache` entirelyLibravatar Michael Haggerty1-27/+2
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>
2017-09-25ref_store: implement `refs_peel_ref()` genericallyLibravatar Michael Haggerty3-77/+0
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>
2017-09-25packed_read_raw_ref(): read the reference from the mmapped bufferLibravatar Michael Haggerty1-5/+9
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>
2017-09-25packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`Libravatar Michael Haggerty1-3/+106
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>
2017-09-25read_packed_refs(): ensure that references are ordered when readLibravatar Michael Haggerty1-11/+212
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>
2017-09-25packed_ref_cache: keep the `packed-refs` file mmapped if possibleLibravatar Michael Haggerty1-42/+143
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>
2017-09-25packed-backend.c: reorder some definitionsLibravatar Michael Haggerty1-24/+24
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>
2017-09-25mmapped_ref_iterator_advance(): no peeled value for broken refsLibravatar Michael Haggerty1-2/+8
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>
2017-09-25mmapped_ref_iterator: add iterator over a packed-refs fileLibravatar Michael Haggerty1-55/+152
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>
2017-09-25packed_ref_cache: remember the file-wide peeling stateLibravatar Michael Haggerty1-5/+12
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>
2017-09-25read_packed_refs(): read references with minimal copyingLibravatar Michael Haggerty1-61/+40
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>
2017-09-25Merge branch 'jk/write-in-full-fix'Libravatar Junio C Hamano1-5/+5
Many codepaths did not diagnose write failures correctly when disks go full, due to their misuse of write_in_full() helper function, which have been corrected. * jk/write-in-full-fix: read_pack_header: handle signed/unsigned comparison in read result config: flip return value of store_write_*() notes-merge: use ssize_t for write_in_full() return value pkt-line: check write_in_full() errors against "< 0" convert less-trivial versions of "write_in_full() != len" avoid "write_in_full(fd, buf, len) != len" pattern get-tar-commit-id: check write_in_full() return against 0 config: avoid "write_in_full(fd, buf, len) < len" pattern
2017-09-24refs: pass NULL to refs_resolve_ref_unsafe() if hash is not neededLibravatar René Scharfe1-2/+1
This allows us to get rid of two write-only variables, one of them being a SHA1 buffer. Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-19Merge branch 'mh/packed-ref-transactions'Libravatar Junio C Hamano4-216/+478
Implement transactional update to the packed-ref representation of references. * mh/packed-ref-transactions: files_transaction_finish(): delete reflogs before references packed-backend: rip out some now-unused code files_ref_store: use a transaction to update packed refs t1404: demonstrate two problems with reference transactions files_initial_transaction_commit(): use a transaction for packed refs prune_refs(): also free the linked list files_pack_refs(): use a reference transaction to write packed refs packed_delete_refs(): implement method packed_ref_store: implement reference transactions struct ref_transaction: add a place for backends to store data packed-backend: don't adjust the reference count on lock/unlock