kernel/git - git - PowerEL Git System

Commit Graph

Author	SHA1	Message	Date
Philip Oakley	a43abad1e3	repack.c: LLP64 compatibility, upcast unity for left shift Visual Studio reports C4334 "was 64-bit shift intended" warning because of size mismatch. Promote unity to the matching type to fit with the `&` operator. Signed-off-by: Philip Oakley <philipoakley@iee.email> Signed-off-by: Junio C Hamano <gitster@pobox.com>	3 years ago
Taylor Blau	e6432e0f1f	builtin/repack.c: avoid leaking child arguments `git repack` invokes a handful of child processes: one to write the actual pack, and optionally ones to repack promisor objects and update the MIDX. Most of these are freed automatically by calling `start_command()` (which invokes it on error) and `finish_command()` which calls it automatically. But repack_promisor_objects() can initialize a child_process, populate its array of arguments, and then return from the function before even calling start_command(). Make sure that the prepared list of arguments is freed by calling child_process_clear() ourselves to avoid leaking memory along this path. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	3 years ago
Taylor Blau	324efc90d1	builtin/repack.c: pass `--refs-snapshot` when writing bitmaps To prevent the race described in an earlier patch, generate and pass a reference snapshot to the multi-pack bitmap code, if we are writing one from `git repack`. This patch is mostly limited to creating a temporary file, and then calling for_each_ref(). Except we try to minimize duplicates, since doing so can drastically reduce the size in network-of-forks style repositories. In the kernel's fork network (the repository containing all objects from the kernel and all its forks), deduplicating the references drops the snapshot size from 934 MB to just 12 MB. But since we're handling duplicates in this way, we have to make sure that we preferred references (those listed in pack.preferBitmapTips) before non-preferred ones (to avoid recording an object which is pointed at by a preferred tip as non-preferred). We accomplish this by doing separate passes over the references: first visiting each prefix in pack.preferBitmapTips, and then over the rest of the references. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	6d08b9d4ca	builtin/repack.c: make largest pack preferred When repacking into a geometric series and writing a multi-pack bitmap, it is beneficial to have the largest resulting pack be the preferred object source in the bitmap's MIDX, since selecting the large packs can lead to fewer broken delta chains and better compression. Teach 'git repack' to identify this pack and pass it to the MIDX write machinery in order to mark it as preferred. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	1d89d88d37	builtin/repack.c: support writing a MIDX while repacking Teach `git repack` a new `--write-midx` option for callers that wish to persist a multi-pack index in their repository while repacking. There are two existing alternatives to this new flag, but they don't cover our particular use-case. These alternatives are: - Call 'git multi-pack-index write' after running 'git repack', or - Set 'GIT_TEST_MULTI_PACK_INDEX=1' in your environment when running 'git repack'. The former works, but introduces a gap in bitmap coverage between repacking and writing a new MIDX (since the repack may have deleted a pack included in the existing MIDX, invalidating it altogether). Setting the 'GIT_TEST_' environment variable is obviously unsupported. In fact, even if it were supported officially, it still wouldn't work, because it generates the MIDX after redundant packs have been dropped, leading to the same issue as above. Introduce a new option which eliminates this race by teaching `git repack` to generate the MIDX at the critical point: after the new packs have been written and moved into place, but before the redundant packs have been removed. This option is compatible with `git repack`'s '--bitmap' option (it changes the interpretation to be: "write a bitmap corresponding to the MIDX after one has been generated"). There is a little bit of additional noise in the patch below to avoid repeating ourselves when selecting which packs to delete. Instead of a single loop as before (where we iterate over 'existing_packs', decide if a pack is worth deleting, and if so, delete it), we have two loops (the first where we decide which ones are worth deleting, and the second where we actually do the deleting). This makes it so we have a single check we can make consistently when (1) telling the MIDX which packs we want to exclude, and (2) actually unlinking the redundant packs. There is also a tiny change to short-circuit the body of write_midx_included_packs() when no packs remain in the case of an empty repository. The MIDX code does not handle this, so avoid trying to generate a MIDX covering zero packs in the first place. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	5f18e31f46	builtin/repack.c: extract showing progress to a variable We only ask whether stderr is a tty before calling 'prune_packed_objects()', but the subsequent patch will add another use. Extract this check into a variable so that both can use it without having to call 'isatty()' twice. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	a169166d2b	builtin/repack.c: rename variables that deal with non-kept packs The new variable `existing_kept_packs` (and corresponding parameter `fname_kept_list`) added by the previous patch make it seem like `existing_packs` and `fname_list` are each subsets of the other two respectively. In reality, each pair is disjoint: one stores the packs without .keep files, and the other stores the packs with .keep files. Rename each to more clearly reflect this. Suggested-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	90f838bc36	builtin/repack.c: keep track of existing packs unconditionally In order to be able to write a multi-pack index during repacking, `git repack` must keep track of which packs it wants to write into the MIDX. This set is the union of existing packs which will not be deleted, new pack(s) generated as a result of the repack, and .keep packs. Prior to this patch, `git repack` populated the list of existing packs only when repacking all-into-one (i.e., with `-A` or `-a`), but we will soon need to know this list when repacking when writing a MIDX without a-i-o. Populate the list of existing packs unconditionally, and guard removing packs from that list only when repacking a-i-o. Additionally, keep track of filenames of kept packs separately, since this, too, will be used in an upcoming patch. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	08944d1c22	midx: preliminary support for `--refs-snapshot` To figure out which commits we can write a bitmap for, the multi-pack index/bitmap code does a reachability traversal, marking any commit which can be found in the MIDX as eligible to receive a bitmap. This approach will cause a problem when multi-pack bitmaps are able to be generated from `git repack`, since the reference tips can change during the repack. Even though we ignore commits that don't exist in the MIDX (when doing a scan of the ref tips), it's possible that a commit in the MIDX reaches something that isn't. This can happen when a multi-pack index contains some pack which refers to loose objects (e.g., if a pack was pushed after starting the repack but before generating the MIDX which depends on an object which is stored as loose in the repository, and by definition isn't included in the multi-pack index). By taking a snapshot of the references before we start repacking, we can close that race window. In the above scenario (where we have a packed object pointing at a loose one), we'll either (a) take a snapshot of the references before seeing the packed one, or (b) take it after, at which point we can guarantee that the loose object will be packed and included in the MIDX. This patch does just that. It writes a temporary "reference snapshot", which is a list of OIDs that are at the ref tips before writing a multi-pack bitmap. References that are "preferred" (i.e,. are a suffix of at least one value of the 'pack.preferBitmapTips' configuration) are marked with a special '+'. The format is simple: one line per commit at each tip, with an optional '+' at the beginning (for preferred references, as described above). When provided, the reference snapshot is used to drive bitmap selection instead of the MIDX code doing its own traversal. When it isn't provided, the usual traversal takes place instead. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Jeff King	5d1f5b8cd4	repack, prune: drop GIT_REF_PARANOIA settings Now that GIT_REF_PARANOIA is the default, we don't need to selectively enable it for destructive operations. In fact, it's harmful to do so, because it overrides any GIT_REF_PARANOIA=0 setting that the user may have provided (because they're trying to work around some corruption). With these uses gone, we can further clean up the ref_paranoia global, and make it a static variable inside the refs code. Signed-off-by: Jeff King <peff@peff.net> Reviewed-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	4e58cedd94	builtin/repack.c: move `.idx` files into place last In a similar spirit as the previous patch, fix the identical problem from `git repack` (which invokes `pack-objects` with a temporary location for output, and then moves the files into their final locations itself). Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	ff1e653c8e	midx: respect 'GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP' Introduce a new 'GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP' environment variable to also write a multi-pack bitmap when 'GIT_TEST_MULTI_PACK_INDEX' is set. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Rafael Silva	a643157d5a	repack: avoid loosening promisor objects in partial clones When `git repack -A -d` is run in a partial clone, `pack-objects` is invoked twice: once to repack all promisor objects, and once to repack all non-promisor objects. The latter `pack-objects` invocation is with --exclude-promisor-objects and --unpack-unreachable, which loosens all objects unused during this invocation. Unfortunately, this includes promisor objects. Because the -d argument to `git repack` subsequently deletes all loose objects also in packs, these just-loosened promisor objects will be immediately deleted. However, this extra disk churn is unnecessary in the first place. For example, in a newly-cloned partial repo that filters all blob objects (e.g. `--filter=blob:none`), `repack` ends up unpacking all trees and commits into the filesystem because every object, in this particular case, is a promisor object. Depending on the repo size, this increases the disk usage considerably: In my copy of the linux.git, the object directory peaked 26GB of more disk usage. In order to avoid this extra disk churn, pass the names of the promisor packfiles as --keep-pack arguments to the second invocation of `pack-objects`. This informs `pack-objects` that the promisor objects are already in a safe packfile and, therefore, do not need to be loosened. For testing, we need to validate whether any object was loosened. However, the "evidence" (loosened objects) is deleted during the process which prevents us from inspecting the object directory. Instead, let's teach `pack-objects` to count loosened objects and emit via trace2 thus allowing inspecting the debug events after the process is finished. This new event is used on the added regression test. Lastly, add a new perf test to evaluate the performance impact made by this changes (tested on git.git): Test HEAD^ HEAD ---------------------------------------------------------- 5600.3: gc 134.38(41.93+90.95) 7.80(6.72+1.35) -94.2% For a bigger repository, such as linux.git, the improvement is even bigger: Test HEAD^ HEAD ------------------------------------------------------------------- 5600.3: gc 6833.00(918.07+3162.74) 268.79(227.02+39.18) -96.1% These improvements are particular big because every object in the newly-cloned partial repository is a promisor object. Reported-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Jeff King <peff@peff.net> Helped-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Rafael Silva <rafaeloliveira.cs@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	9218c6a40c	midx: allow marking a pack as preferred When multiple packs in the multi-pack index contain the same object, the MIDX machinery must make a choice about which pack it associates with that object. Prior to this patch, the lowest-ordered[1] pack was always selected. Pack selection for duplicate objects is relatively unimportant today, but it will become important for multi-pack bitmaps. This is because we can only invoke the pack-reuse mechanism when all of the bits for reused objects come from the reuse pack (in order to ensure that all reused deltas can find their base objects in the same pack). To encourage the pack selection process to prefer one pack over another (the pack to be preferred is the one a caller would like to later use as a reuse pack), introduce the concept of a "preferred pack". When provided, the MIDX code will always prefer an object found in a preferred pack over any other. No format changes are required to store the preferred pack, since it will be able to be inferred with a corresponding MIDX bitmap, by looking up the pack associated with the object in the first bit position (this ordering is described in detail in a subsequent commit). [1]: the ordering is specified by MIDX internals; for our purposes we can consider the "lowest ordered" pack to be "the one with the most-recent mtime. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Junio C Hamano	ccae01cab8	builtin/repack.c: reword comment around pack-objects flags The comment in this block is meant to indicate that passing '--all', '--reflog', and so on aren't necessary when repacking with the '--geometric' option. But, it has two problems: first, it is factually incorrect ('--all' is not incompatible with '--stdin-packs' as the comment suggests); second, it is quite focused on the geometric case for a block that is guarding against it. Reword this comment to address both issues. Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	2a15964128	builtin/repack.c: be more conservative with unsigned overflows There are a number of places in the geometric repack code where we multiply the number of objects in a pack by another unsigned value. We trust that the number of objects in a pack is always representable by a uint32_t, but we don't necessarily trust that that number can be multiplied without overflow. Sprinkle some unsigned_add_overflows() and unsigned_mult_overflows() in split_pack_geometry() to check that we never overflow any unsigned types when adding or multiplying them. Arguably these checks are a little too conservative, and certainly they do not help the readability of this function. But they are serving a useful purpose, so I think they are worthwhile overall. Suggested-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	13d746a303	builtin/repack.c: assign pack split later To determine the where to place the split when repacking with the '--geometric' option, split_pack_geometry() assigns the "split" variable and then decrements it in a loop. It would be equivalent (and more readable) to assign the split to the loop position after exiting the loop, so do that instead. Suggested-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	f25e33c156	builtin/repack.c: do not repack single packs with --geometric In `0fabafd0b9` (builtin/repack.c: add '--geometric' option, 2021-02-22), the 'git repack --geometric' code aborts early when there is zero or one pack. When there are no packs, this code does the right thing by placing the split at "0". But when there is exactly one pack, the split is placed at "1", which means that "git repack --geometric" (with any factor) repacks all of the objects in a single pack. This is wasteful, and the remaining code in split_pack_geometry() does the right thing (not repacking the objects in a single pack) even when only one pack is present. Loosen the guard to only stop when there aren't any packs, and let the rest of the code do the right thing. Add a test to ensure that this is the case. Noticed-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	0fabafd0b9	builtin/repack.c: add '--geometric' option Often it is useful to both: - have relatively few packfiles in a repository, and - avoid having so few packfiles in a repository that we repack its entire contents regularly This patch implements a '--geometric=<n>' option in 'git repack'. This allows the caller to specify that they would like each pack to be at least a factor times as large as the previous largest pack (by object count). Concretely, say that a repository has 'n' packfiles, labeled P1, P2, ..., up to Pn. Each packfile has an object count equal to 'objects(Pn)'. With a geometric factor of 'r', it should be that: objects(Pi) > r*objects(P(i-1)) for all i in [1, n], where the packs are sorted by objects(P1) <= objects(P2) <= ... <= objects(Pn). Since finding a true optimal repacking is NP-hard, we approximate it along two directions: 1. We assume that there is a cutoff of packs _before starting the repack_ where everything to the right of that cut-off already forms a geometric progression (or no cutoff exists and everything must be repacked). 2. We assume that everything smaller than the cutoff count must be repacked. This forms our base assumption, but it can also cause even the "heavy" packs to get repacked, for e.g., if we have 6 packs containing the following number of objects: 1, 1, 1, 2, 4, 32 then we would place the cutoff between '1, 1' and '1, 2, 4, 32', rolling up the first two packs into a pack with 2 objects. That breaks our progression and leaves us: 2, 1, 2, 4, 32 ^ (where the '^' indicates the position of our split). To restore a progression, we move the split forward (towards larger packs) joining each pack into our new pack until a geometric progression is restored. Here, that looks like: 2, 1, 2, 4, 32 ~> 3, 2, 4, 32 ~> 5, 4, 32 ~> ... ~> 9, 32 ^ ^ ^ ^ This has the advantage of not repacking the heavy-side of packs too often while also only creating one new pack at a time. Another wrinkle is that we assume that loose, indexed, and reflog'd objects are insignificant, and lump them into any new pack that we create. This can lead to non-idempotent results. Suggested-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	2f4ba2a867	packfile: prepare for the existence of '.rev' files Specify the format of the on-disk reverse index 'pack-.rev' file, as well as prepare the code for the existence of such files. The reverse index maps from pack relative positions (i.e., an index into the array of object which is sorted by their offsets within the packfile) to their position within the 'pack-.idx' file. Today, this is done by building up a list of (off_t, uint32_t) tuples for each object (the off_t corresponding to that object's offset, and the uint32_t corresponding to its position in the index). To convert between pack and index position quickly, this array of tuples is radix sorted based on its offset. This has two major drawbacks: First, the in-memory cost scales linearly with the number of objects in a pack. Each 'struct revindex_entry' is sizeof(off_t) + sizeof(uint32_t) + padding bytes for a total of 16. To observe this, force Git to load the reverse index by, for e.g., running 'git cat-file --batch-check="%(objectsize:disk)"'. When asking for a single object in a fresh clone of the kernel, Git needs to allocate 120+ MB of memory in order to hold the reverse index in memory. Second, the cost to sort also scales with the size of the pack. Luckily, this is a linear function since 'load_pack_revindex()' uses a radix sort, but this cost still must be paid once per pack per process. As an example, it takes ~60x longer to print the _size_ of an object as it does to print that entire object's _contents_: Benchmark #1: git.compile cat-file --batch <obj Time (mean ± σ): 3.4 ms ± 0.1 ms [User: 3.3 ms, System: 2.1 ms] Range (min … max): 3.2 ms … 3.7 ms 726 runs Benchmark #2: git.compile cat-file --batch-check="%(objectsize:disk)" <obj Time (mean ± σ): 210.3 ms ± 8.9 ms [User: 188.2 ms, System: 23.2 ms] Range (min … max): 193.7 ms … 224.4 ms 13 runs Instead, avoid computing and sorting the revindex once per process by writing it to a file when the pack itself is generated. The format is relatively straightforward. It contains an array of uint32_t's, the length of which is equal to the number of objects in the pack. The ith entry in this table contains the index position of the ith object in the pack, where "ith object in the pack" is determined by pack offset. One thing that the on-disk format does _not_ contain is the full (up to) eight-byte offset corresponding to each object. This is something that the in-memory revindex contains (it stores an off_t in 'struct revindex_entry' along with the same uint32_t that the on-disk format has). Omit it in the on-disk format, since knowing the index position for some object is sufficient to get a constant-time lookup in the pack-.idx file to ask for an object's offset within the pack. This trades off between the on-disk size of the 'pack-.rev' file for runtime to chase down the offset for some object. Even though the lookup is constant time, the constant is heavier, since it can potentially involve two pointer walks in v2 indexes (one to access the 4-byte offset table, and potentially a second to access the double wide offset table). Consider trying to map an object's pack offset to a relative position within that pack. In a cold-cache scenario, more page faults occur while switching between binary searching through the reverse index and searching through the .idx file for an object's offset. Sure enough, with a cold cache (writing '3' into '/proc/sys/vm/drop_caches' after 'sync'ing), printing out the entire object's contents is still marginally faster than printing its size: Benchmark #1: git.compile cat-file --batch-check="%(objectsize:disk)" <obj >/dev/null Time (mean ± σ): 22.6 ms ± 0.5 ms [User: 2.4 ms, System: 7.9 ms] Range (min … max): 21.4 ms … 23.5 ms 41 runs Benchmark #2: git.compile cat-file --batch <obj >/dev/null Time (mean ± σ): 17.2 ms ± 0.7 ms [User: 2.8 ms, System: 5.5 ms] Range (min … max): 15.6 ms … 18.2 ms 45 runs (Numbers taken in the kernel after cheating and using the next patch to generate a reverse index). There are a couple of approaches to improve cold cache performance not pursued here: - We could include the object offsets in the reverse index format. Predictably, this does result in fewer page faults, but it triples the size of the file, while simultaneously duplicating a ton of data already available in the .idx file. (This was the original way I implemented the format, and it did show `--batch-check='%(objectsize:disk)'` winning out against `--batch`.) On the other hand, this increase in size also results in a large block-cache footprint, which could potentially hurt other workloads. - We could store the mapping from pack to index position in more cache-friendly way, like constructing a binary search tree from the table and writing the values in breadth-first order. This would result in much better locality, but the price you pay is trading O(1) lookup in 'pack_pos_to_index()' for an O(log n) one (since you can no longer directly index the table). So, neither of these approaches are taken here. (Thankfully, the format is versioned, so we are free to pursue these in the future.) But, cold cache performance likely isn't interesting outside of one-off cases like asking for the size of an object directly. In real-world usage, Git is often performing many operations in the revindex (i.e., asking about many objects rather than a single one). The trade-off is worth it, since we will avoid the vast majority of the cost of generating the revindex that the extra pointer chase will look like noise in the following patch's benchmarks. This patch describes the format and prepares callers (like in pack-revindex.c) to be able to read *.rev files once they exist. An implementation of the writer will appear in the next patch, and callers will gradually begin to start using the writer in the patches that follow after that. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Christian Couder	33add2ad7d	fetch-pack: refactor writing promisor file Let's replace the 2 different pieces of code that write a promisor file in 'builtin/repack.c' and 'fetch-pack.c' with a new function called 'write_promisor_file()' in 'pack-write.c' and 'pack.h'. This might also help us in the future, if we want to put back the ref names and associated hashes that were in the promisor files we are repacking in 'builtin/repack.c' as suggested by a NEEDSWORK comment just above the code we are refactoring. Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	2fcb03b52d	builtin/repack.c: don't move existing packs out of the way When 'git repack' creates a pack with the same name as any existing pack, it moves the existing one to 'old-pack-xxx.{pack,idx,...}' and then renames the new one into place. Eventually, it would be nice to have 'git repack' allow for writing a multi-pack index at the critical time (after the new packs have been written / moved into place, but before the old ones have been deleted). Guessing that this option might be called '--write-midx', this makes the following situation (where repacks are issued back-to-back without any new objects) impossible: $ git repack -adb $ git repack -adb --write-midx In the second repack, the existing packs are overwritten verbatim with the same rename-to-old sequence. At that point, the current MIDX is invalidated, since it refers to now-missing packs. So that code wants to be run after the MIDX is re-written. But (prior to this patch) the new MIDX can't be written until the new packs are moved into place. So, we have a circular dependency. This is all hypothetical, since no code currently exists to write a MIDX safely during a 'git repack' (the 'GIT_TEST_MULTI_PACK_INDEX' does so unsafely). Putting hypothetical aside, though: why do we need to rename existing packs to be prefixed with 'old-' anyway? This behavior dates all the way back to `2ad47d6` (git-repack: Be careful when updating the same pack as an existing one., 2006-06-25). `2ad47d6` is mainly concerned about a case where a newly written pack would have a different structure than its index. This used to be possible when the pack name was a hash of the set of objects. Under this naming scheme, two packs that store the same set of objects could differ in delta selection, object positioning, or both. If this happened, then any such packs would be unreadable in the instant between copying the new pack and new index (i.e., either the index or pack will be stale depending on the order that they were copied). But since `1190a1a` (pack-objects: name pack files after trailer hash, 2013-12-05), this is no longer possible, since pack files are named not after their logical contents (i.e., the set of objects), but by the actual checksum of their contents. So, this old- behavior can safely go, which allows us to avoid our circular dependency above. In addition to avoiding the circular dependency, this patch also makes 'git repack' a lot simpler, since we don't have to deal with failures encountered when renaming existing packs to be prefixed with 'old-'. This patch is mostly limited to removing code paths that deal with the 'old' prefixing, with the exception of files that include the pack's name in their own filename, like .idx, .bitmap, and related files. The exception is that we want to continue to trust what pack-objects wrote. That is, it is not the case that we pretend as if pack-objects didn't write files identical to ones that already exist, but rather that we respect what pack-objects wrote as the source of truth. That cuts two ways: - If pack-objects produced an identical pack to one that already exists with a bitmap, but did not produce a bitmap, we remove the bitmap that already exists. (This behavior is codified in t7700.14). - If pack-objects produced an identical pack to one that already exists, we trust the just-written version of the coresponding .idx, .promisor, and other files over the ones that already exist. This ensures that we use the most up-to-date versions of this files, which is safe even in the face of format changes in, say, the .idx file (which would not be reflected in the .idx file's name). Helped-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	704c4a5c07	builtin/repack.c: keep track of what pack-objects wrote In the subsequent commit, it will become useful to keep track of which metadata files were written by pack-objects. We already do this to an extent with the 'exts' array, which only is used in the context of existing packs. Co-authored-by: Jeff King <peff@peff.net> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Jeff King	63f4d5cf57	repack: make "exts" array available outside cmd_repack() We'll use it in a helper function soon. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	4 years ago
Taylor Blau	59552fb3e2	midx: traverse the local MIDX first When a repository has an alternate object directory configured, callers can traverse through each alternate's MIDX by walking the '->next' pointer. But, when 'prepare_multi_pack_index_one()' loads multiple MIDXs, it places the new ones at the front of this pointer chain, not at the end. This can be confusing for callers such as 'git repack -ad', causing test failures like in t7700.6 with 'GIT_TEST_MULTI_PACK_INDEX=1'. The occurs when dropping a pack known to the local MIDX with alternates configured that have their own MIDX. Since the alternate's MIDX is returned via 'get_multi_pack_index()', 'midx_contains_pack()' returns true (which is correct, since it traverses through the '->next' pointer to find the MIDX in the chain that does contain the requested object). But, we call 'clear_midx_file()' on 'the_repository', which drops the MIDX at the path of the first MIDX in the chain, which (in the case of t7700.6 is the one in the alternate). This patch addresses that by: - placing the local MIDX first in the chain when calling 'prepare_multi_pack_index_one()', and - introducing a new 'get_local_multi_pack_index()', which explicitly returns the repository-local MIDX, if any. Don't impose an additional order on the MIDX's '->next' pointer beyond that the first item in the chain must be local if one exists so that we avoid a quadratic insertion. Likewise, use 'get_local_multi_pack_index()' in 'remove_redundant_pack()' to fix the formerly broken t7700.6 when run with 'GIT_TEST_MULTI_PACK_INDEX=1'. Finally, note that the MIDX ordering invariant is only preserved by the insertion order in 'prepare_packed_git()', which traverses through the ODB's '->next' pointer, meaning we visit the local object store first. This fragility makes this an undesirable long-term solution if more callers are added, but it is acceptable for now since this is the only caller. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Taylor Blau	e08f7bb093	builtin/repack.c: invalidate MIDX only when necessary In `525e18c04b` (midx: clear midx on repack, 2018-07-12), 'git repack' learned to remove a multi-pack-index file if it added or removed a pack from the object store. This mechanism is a little over-eager, since it is only necessary to drop a MIDX if 'git repack' removes a pack that the MIDX references. Adding a pack outside of the MIDX does not require invalidating the MIDX, and likewise for removing a pack the MIDX does not know about. Teach 'git repack' to check for this by loading the MIDX, and checking whether the to-be-removed pack is known to the MIDX. This requires a slightly odd alternation to a test in t5319, which is explained with a comment. A new test is added to show that the MIDX is left alone when both packs known to it are marked as .keep, but two packs unknown to it are removed and combined into one new pack. Helped-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Jeff King	f6d8942b1f	strvec: fix indentation in renamed calls Code which split an argv_array call across multiple lines, like: argv_array_pushl(&args, "one argument", "another argument", "and more", NULL); was recently mechanically renamed to use strvec, which results in mis-matched indentation like: strvec_pushl(&args, "one argument", "another argument", "and more", NULL); Let's fix these up to align the arguments with the opening paren. I did this manually by sifting through the results of: git jump grep 'strvec_.*,$' and liberally applying my editor's auto-format. Most of the changes are of the form shown above, though I also normalized a few that had originally used a single-tab indentation (rather than our usual style of aligning with the open paren). I also rewrapped a couple of obvious cases (e.g., where previously too-long lines became short enough to fit on one), but I wasn't aggressive about it. In cases broken to three or more lines, the grouping of arguments is sometimes meaningful, and it wasn't worth my time or reviewer time to ponder each case individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Jeff King	22f9b7f3f5	strvec: convert builtin/ callers away from argv_array name We eventually want to drop the argv_array name and just use strvec consistently. There's no particular reason we have to do it all at once, or care about interactions between converted and unconverted bits. Because of our preprocessor compat layer, the names are interchangeable to the compiler (so even a definition and declaration using different names is OK). This patch converts all of the files in builtin/ to keep the diff to a manageable size. The conversion was done purely mechanically with: git ls-files '.c' '.h' \| xargs perl -i -pe ' s/ARGV_ARRAY/STRVEC/g; s/argv_array/strvec/g; ' and then selectively staging files with "git add builtin/". We'll deal with any indentation/style fallouts separately. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Jeff King	dbbcd44fb4	strvec: rename files from argv-array to strvec This requires updating #include lines across the code-base, but that's all fairly mechanical, and was done with: git ls-files '.c' '.h' \| xargs perl -i -pe 's/argv-array.h/strvec.h/' Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Taylor Blau	120ad2b0f1	shallow: extract a header file for shallow-related functions There are many functions in commit.h that are more related to shallow repositories than they are to any sort of generic commit machinery. Likely this began when there were only a few shallow-related functions, and commit.h seemed a reasonable enough place to put them. But, now there are a good number of shallow-related functions, and placing them all in 'commit.h' doesn't make sense. This patch extracts a 'shallow.h', which takes all of the declarations from 'commit.h' for functions which already exist in 'shallow.c'. We will bring the remaining shallow-related functions defined in 'commit.c' in a subsequent patch. For now, move only the ones that already are implemented in 'shallow.c', and update the necessary includes. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Denton Liu	9460fd48b5	Lib-ify prune-packed In builtin.h, there exists the distinctly lib-ish function prune_packed_objects(). This function can currently only be called by built-in commands but, unlike all of the other functions in the header, it does not make sense to impose this restriction as the functionality can be logically reused in libgit. Extract this function into prune-packed.c so that related definitions can exist clearly in their own header file. While we're at it, clean up #includes that are unused. This patch is best viewed with --color-moved. Signed-off-by: Denton Liu <liu.denton@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
William Baker	efbc3aee08	midx: add MIDX_PROGRESS flag Add the MIDX_PROGRESS flag and update the write\|verify\|expire\|repack functions in midx.h to accept a flags parameter. The MIDX_PROGRESS flag indicates whether the caller of the function would like progress information to be displayed. This patch only changes the method prototypes and does not change the functionality. The functionality change will be handled by a later patch. Signed-off-by: William Baker <William.Baker@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Jonathan Tan	5374a290aa	fetch-pack: write fetched refs to .promisor The specification of promisor packfiles (in partial-clone.txt) states that the .promisor files that accompany packfiles do not matter (just like .keep files), so whenever a packfile is fetched from the promisor remote, Git has been writing empty .promisor files. But these files could contain more useful information. So instead of writing empty files, write the refs fetched to these files. This makes it easier to debug issues with partial clones, as we can identify what refs (and their associated hashes) were fetched at the time the packfile was downloaded, and if necessary, compare those hashes against what the promisor remote reports now. This is implemented by teaching fetch-pack to write its own non-empty .promisor file whenever it knows the name of the pack's lockfile. This covers the case wherein the user runs "git fetch" with an internal protocol or HTTP protocol v2 (fetch_refs_via_pack() in transport.c sets lock_pack) and with HTTP protocol v0/v1 (fetch_git() in remote-curl.c passes "--lock-pack" to "fetch-pack"). Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Acked-by: Josh Steadmon <steadmon@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
brian m. carlson	dd336a5511	builtin/repack: write object IDs of the proper length Use the_hash_algo when calling xwrite with a hex object ID so that the proper amount of data is written. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Jeff King	7ff024e7b3	repack: simplify handling of auto-bitmaps and .keep files Commit `7328482253` (repack: disable bitmaps-by-default if .keep files exist, 2019-06-29) taught repack to prefer disabling bitmaps to duplicating objects (unless bitmaps were asked for explicitly). But there's an easier way to do this: if we keep passing the --honor-pack-keep flag to pack-objects when auto-enabling bitmaps, then pack-objects already makes the same decision (it will disable bitmaps rather than duplicate). Better still, pack-objects can actually decide to do so based not just on the presence of a .keep file, but on whether that .keep file actually impacts the new pack we're making (so if we're racing with a push or fetch, for example, their temporary .keep file will not block us from generating bitmaps if they haven't yet updated their refs). And because repack uses the --write-bitmap-index-quiet flag, we don't have to worry about pack-objects generating confusing warnings when it does see a .keep file. We can confirm this by tweaking the .keep test to check repack's stderr. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Jeff King	25575015ca	repack: silence warnings when auto-enabled bitmaps cannot be built Depending on various config options, a full repack may not be able to build a reachability bitmap index (e.g., if pack.packSizeLimit forces us to write multiple packs). In these cases pack-objects may write a warning to stderr. Since `36eba0323d` (repack: enable bitmaps by default on bare repos, 2019-03-14), we may generate these warnings even when the user did not explicitly ask for bitmaps. This has two downsides: - it can be confusing, if they don't know what bitmaps are - a daemonized auto-gc will write this to its log file, and the presence of the warning may suppress further auto-gc (until gc.logExpiry has elapsed) Let's have repack communicate to pack-objects that the choice to turn on bitmaps was not made explicitly by the user, which in turn allows pack-objects to suppress these warnings. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Eric Wong	7328482253	repack: disable bitmaps-by-default if .keep files exist Bitmaps aren't useful with multiple packs, and users with .keep files ended up with redundant packs when bitmaps got enabled by default in bare repos. So detect when .keep files exist and stop enabling bitmaps by default in that case. Wasteful (but otherwise harmless) race conditions with .keep files documented by Jeff King still apply and there's a chance we'd still end up with redundant data on the FS: https://public-inbox.org/git/20190623224244.GB1100@sigill.intra.peff.net/ v2: avoid subshell in test case, be multi-index aware Fixes: `36eba0323d` ("repack: enable bitmaps by default on bare repos") Signed-off-by: Eric Wong <e@80x24.org> Helped-by: Jeff King <peff@peff.net> Reported-by: Janos Farkas <chexum@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Christian Couder	b14ed5adaf	Use promisor_remote_get_direct() and has_promisor_remote() Instead of using the repository_format_partial_clone global and fetch_objects() directly, let's use has_promisor_remote() and promisor_remote_get_direct(). This way all the configured promisor remotes will be taken into account, not only the one specified by extensions.partialClone. Also when cloning or fetching using a partial clone filter, remote.origin.promisor will be set to "true" instead of setting extensions.partialClone to "origin". This makes it possible to use many promisor remote just by fetching from them. Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Derrick Stolee	2d511cfc0b	packfile: rename close_all_packs to close_object_store The close_all_packs() method is now responsible for more than just pack-files. It also closes the commit-graph and the multi-pack-index. Rename the function to be more descriptive of its larger role. The name also fits because the input parameter is a raw_object_store. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Derrick Stolee	8434e85d5f	repack: refactor pack deletion for future use The repack builtin deletes redundant pack-files and their associated .idx, .promisor, .bitmap, and .keep files. We will want to re-use this logic in the future for other types of repack, so pull the logic into 'unlink_pack_path()' in packfile.c. The 'ignore_keep' parameter is enabled for the use in repack, but will be important for a future caller. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Eric Wong	36eba0323d	repack: enable bitmaps by default on bare repos A typical use case for bare repos is for serving clones and fetches to clients. Enable bitmaps by default on bare repos to make it easier for admins to host git repos in a performant way. Signed-off-by: Eric Wong <e@80x24.org> Helped-by: Jeff King <peff@peff.net> Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Johannes Schindelin	5bdece0d70	gc/repack: release packs when needed On Windows, files cannot be removed nor renamed if there are still handles held by a process. To remedy that, we introduced the close_all_packs() function. Earlier, we made sure that the packs are released just before `git gc` is spawned, in case that gc wants to remove no-longer needed packs. But this developer forgot that gc itself also needs to let go of packs, e.g. when consolidating all packs via the --aggressive option. Likewise, `git repack -d` wants to delete obsolete packs and therefore needs to close all pack handles, too. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Nguyễn Thái Ngọc Duy	c83d950e59	repack: mark more strings for translation Two strings are slightly updated to be consistent with the rest: die() starts with lowercase. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Johannes Schindelin	5dcfbf564c	repack -ad: prune the list of shallow commits `git repack` can drop unreachable commits without further warning, making the corresponding entries in `.git/shallow` invalid, which causes serious problems when deepening the branches. One scenario where unreachable commits are dropped by `git repack` is when a `git fetch --prune` (or even a `git fetch` when a ref was force-pushed in the meantime) can make a commit unreachable that was reachable before. Therefore it is not safe to assume that a `git repack -adlf` will keep unreachable commits alone (under the assumption that they had not been packed in the first place, which is an assumption at least some of Git's code seems to make). This is particularly important to keep in mind when looking at the `.git/shallow` file: if any commits listed in that file become unreachable, it is not a problem, but if they go missing, it is a problem. One symptom of this problem is that a deepening fetch may now fail with fatal: error in object: unshallow <commit-hash> To avoid this problem, let's prune the shallow list in `git repack` when the `-d` option is passed, unless `-A` is passed, too (which would force the now-unreachable objects to be turned into loose objects instead of being deleted). Additionally, we also need to take `--keep-reachable` and `--unpack-unreachable=<date>` into account. Note: an alternative solution discussed during the review of this patch was to teach `git fetch` to simply ignore entries in .git/shallow if the corresponding commits do not exist locally. A quick test, however, revealed that the .git/shallow file is written during a shallow clone, in which case the commits do not exist, either, but the "shallow" line does need to be sent. Therefore, this approach would be a lot more finicky than the approach presented by the this patch. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Derrick Stolee	0465a50506	multi-pack-index: define GIT_TEST_MULTI_PACK_INDEX The multi-pack-index feature is tested in isolation by t5319-multi-pack-index.sh, but there are many more interesting scenarios in the test suite surrounding pack-file data shapes and interactions. Since the multi-pack-index is an optional data structure, it does not make sense to include it by default in those tests. Instead, add a new GIT_TEST_MULTI_PACK_INDEX environment variable that enables core.multiPackIndex and writes a multi-pack-index after each 'git repack' command. This adds extra test coverage when needed. There are a few spots in the test suite that need to react to this change: * t5319-multi-pack-index.sh: there is a test that checks that 'git repack' deletes the multi-pack-index. Disable the environment variable to ensure this still happens. * t5310-pack-bitmaps.sh: One test moves a pack-file from the object directory to an alternate. This breaks the multi-pack-index, so delete the multi-pack-index at this point, if it exists. * t9300-fast-import.sh: One test verifies the number of files in the .git/objects/pack directory is exactly 8. Exclude the multi-pack-index from this count so it is still 8 in all cases. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
Derrick Stolee	1dcd9f2043	midx: close multi-pack-index on repack When repacking, we may remove pack-files. This invalidates the multi-pack-index (if it exists). Previously, we removed the multi-pack-index file before removing any pack-file. In some cases, the repack command may load the multi-pack-index into memory. This may lead to later in-memory references to the non-existent pack- files. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
brian m. carlson	2f0c9e9a9b	builtin/repack: replace hard-coded constants Note that while the error messages here are not translated, the end user should never see them. We invoke git pack-objects shortly before both invocations, so we can be fairly certain that the data we're receiving is in fact valid. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
Jeff King	16d75fa48d	repack: add delta-islands support Implement simple support for --delta-islands option and repack.useDeltaIslands config variable in git repack. This allows users to setup delta islands in their config and get the benefit of less disk usage while cloning and fetching is still quite fast and not much more CPU intensive. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
Jonathan Tan	5d19e8138d	repack: repack promisor objects if -a or -A is set Currently, repack does not touch promisor packfiles at all, potentially causing the performance of repositories that have many such packfiles to drop. Therefore, repack all promisor objects if invoked with -a or -A. This is done by an additional invocation of pack-objects on all promisor objects individually given, which takes care of deduplication and allows the resulting packfiles to respect flags such as --max-pack-size. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
Jonathan Tan	2b958e790b	repack: refactor setup of pack-objects cmd A subsequent patch will teach repack to run pack-objects with some same and some different arguments if repacking of promisor objects is required. Refactor the setup of the pack-objects cmd so that setting up the arguments common to both is done in a function. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago

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124 Commits (0d7131763e7762dc34c407f32e3c63123001a292)