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If a filesystem-level corruption occurs in a .bitmap file, Git can react poorly. This could take the form of a run-time error due to failing to parse an EWAH bitmap or be more subtle such as returning the wrong set of objects to a fetch or clone. A natural first response to either of these kinds of errors is to run 'git fsck' to see if any files are corrupt. This currently ignores all .bitmap files. Add checks to 'git fsck' for all .bitmap files that are currently associated with a multi-pack-index or pack file. Verify their checksums using the hashfile API. We iterate through all multi-pack-indexes and pack-files to be sure to check all .bitmap files, not just the one that would be read by the process. For example, a multi-pack-index bitmap overrules a pack-bitmap. However, if the multi-pack-index is removed, the pack-bitmap may be selected instead. Be thorough to include every file that could become active in such a way. This includes checking files in alternates. There is potential that we could extend this effort to check the structure of the reachability bitmaps themselves, but it is very expensive to do so. At minimum, it's as expensive as generating the bitmaps in the first place, and that's assuming that we don't use the trivial algorithm of verifying each bitmap individually. The trivial algorithm will result in quadratic behavior (number of objects times number of bitmapped commits) while the bitmap building operation constructs a lattice of commits to build bitmaps incrementally and then generate the final bitmaps from a subset of those commits. If we were to extend 'git fsck' to check .bitmap file contents more closely like this, then we would likely want to hide it behind an option that signals the user is more willing to do expensive operations such as this. For testing, set up a repository with a pack-bitmap _and_ a multi-pack-index bitmap. This requires some file movement to avoid deleting the pack-bitmap during the repack that creates the multi-pack-index bitmap. We can then verify that 'git fsck' is checking all files, not just the "active" bitmap. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
117 lines
3.7 KiB
C
117 lines
3.7 KiB
C
#ifndef PACK_BITMAP_H
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#define PACK_BITMAP_H
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#include "ewah/ewok.h"
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#include "khash.h"
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#include "pack.h"
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#include "pack-objects.h"
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#include "string-list.h"
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struct commit;
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struct repository;
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struct rev_info;
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static const char BITMAP_IDX_SIGNATURE[] = {'B', 'I', 'T', 'M'};
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struct bitmap_disk_header {
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char magic[ARRAY_SIZE(BITMAP_IDX_SIGNATURE)];
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uint16_t version;
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uint16_t options;
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uint32_t entry_count;
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unsigned char checksum[GIT_MAX_RAWSZ];
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};
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#define NEEDS_BITMAP (1u<<22)
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/*
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* The width in bytes of a single triplet in the lookup table
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* extension:
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* (commit_pos, offset, xor_row)
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*
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* whose fields ar 32-, 64-, 32- bits wide, respectively.
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*/
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#define BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH (16)
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enum pack_bitmap_opts {
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BITMAP_OPT_FULL_DAG = 0x1,
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BITMAP_OPT_HASH_CACHE = 0x4,
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BITMAP_OPT_LOOKUP_TABLE = 0x10,
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};
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enum pack_bitmap_flags {
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BITMAP_FLAG_REUSE = 0x1
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};
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typedef int (*show_reachable_fn)(
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const struct object_id *oid,
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enum object_type type,
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int flags,
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uint32_t hash,
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struct packed_git *found_pack,
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off_t found_offset);
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struct bitmap_index;
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struct bitmap_index *prepare_bitmap_git(struct repository *r);
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struct bitmap_index *prepare_midx_bitmap_git(struct multi_pack_index *midx);
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void count_bitmap_commit_list(struct bitmap_index *, uint32_t *commits,
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uint32_t *trees, uint32_t *blobs, uint32_t *tags);
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void traverse_bitmap_commit_list(struct bitmap_index *,
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struct rev_info *revs,
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show_reachable_fn show_reachable);
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void test_bitmap_walk(struct rev_info *revs);
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int test_bitmap_commits(struct repository *r);
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int test_bitmap_hashes(struct repository *r);
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struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs,
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int filter_provided_objects);
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uint32_t midx_preferred_pack(struct bitmap_index *bitmap_git);
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int reuse_partial_packfile_from_bitmap(struct bitmap_index *,
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struct packed_git **packfile,
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uint32_t *entries,
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struct bitmap **reuse_out);
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int rebuild_existing_bitmaps(struct bitmap_index *, struct packing_data *mapping,
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kh_oid_map_t *reused_bitmaps, int show_progress);
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void free_bitmap_index(struct bitmap_index *);
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int bitmap_walk_contains(struct bitmap_index *,
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struct bitmap *bitmap, const struct object_id *oid);
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/*
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* After a traversal has been performed by prepare_bitmap_walk(), this can be
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* queried to see if a particular object was reachable from any of the
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* objects flagged as UNINTERESTING.
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*/
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int bitmap_has_oid_in_uninteresting(struct bitmap_index *, const struct object_id *oid);
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off_t get_disk_usage_from_bitmap(struct bitmap_index *, struct rev_info *);
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void bitmap_writer_show_progress(int show);
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void bitmap_writer_set_checksum(const unsigned char *sha1);
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void bitmap_writer_build_type_index(struct packing_data *to_pack,
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struct pack_idx_entry **index,
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uint32_t index_nr);
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uint32_t *create_bitmap_mapping(struct bitmap_index *bitmap_git,
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struct packing_data *mapping);
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int rebuild_bitmap(const uint32_t *reposition,
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struct ewah_bitmap *source,
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struct bitmap *dest);
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struct ewah_bitmap *bitmap_for_commit(struct bitmap_index *bitmap_git,
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struct commit *commit);
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void bitmap_writer_select_commits(struct commit **indexed_commits,
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unsigned int indexed_commits_nr, int max_bitmaps);
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int bitmap_writer_build(struct packing_data *to_pack);
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void bitmap_writer_finish(struct pack_idx_entry **index,
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uint32_t index_nr,
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const char *filename,
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uint16_t options);
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char *midx_bitmap_filename(struct multi_pack_index *midx);
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char *pack_bitmap_filename(struct packed_git *p);
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int bitmap_is_midx(struct bitmap_index *bitmap_git);
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const struct string_list *bitmap_preferred_tips(struct repository *r);
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int bitmap_is_preferred_refname(struct repository *r, const char *refname);
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int verify_bitmap_files(struct repository *r);
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#endif
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