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![Matheus Tavares](/assets/img/avatar_default.png)
replace-object functions are very close to being thread-safe: the only current racy section is the lazy initialization at prepare_replace_object(). The following patches will protect some object reading operations to be called threaded, but before that, replace functions must be protected. To do so, add a mutex to struct raw_object_store and acquire it before lazy initializing the replace_map. This won't cause any noticeable performance drop as the mutex will no longer be used after the replace_map is initialized. Later, when the replace functions are called in parallel, thread debuggers might point our use of the added replace_map_initialized flag as a data race. However, as this boolean variable is initialized as false and it's only updated once, there's no real harm. It's perfectly fine if the value is updated right after a thread read it in replace-map.h:lookup_replace_object() (there'll only be a performance penalty for the affected threads at that moment). We could cease the debugger warning protecting the variable reading at the said function. However, this would negatively affect performance for all threads calling it, at any time, so it's not really worthy since the warning doesn't represent a real problem. Instead, to make sure we don't get false positives (at ThreadSanitizer, at least) an entry for the respective function is added to .tsan-suppressions. Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br> Signed-off-by: Junio C Hamano <gitster@pobox.com>
409 lines
12 KiB
C
409 lines
12 KiB
C
#ifndef OBJECT_STORE_H
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#define OBJECT_STORE_H
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#include "cache.h"
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#include "oidmap.h"
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#include "list.h"
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#include "sha1-array.h"
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#include "strbuf.h"
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struct object_directory {
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struct object_directory *next;
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/*
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* Used to store the results of readdir(3) calls when we are OK
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* sacrificing accuracy due to races for speed. That includes
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* object existence with OBJECT_INFO_QUICK, as well as
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* our search for unique abbreviated hashes. Don't use it for tasks
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* requiring greater accuracy!
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*
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* Be sure to call odb_load_loose_cache() before using.
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*/
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char loose_objects_subdir_seen[256];
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struct oid_array loose_objects_cache[256];
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/*
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* Path to the alternative object store. If this is a relative path,
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* it is relative to the current working directory.
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*/
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char *path;
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};
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void prepare_alt_odb(struct repository *r);
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char *compute_alternate_path(const char *path, struct strbuf *err);
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typedef int alt_odb_fn(struct object_directory *, void *);
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int foreach_alt_odb(alt_odb_fn, void*);
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typedef void alternate_ref_fn(const struct object_id *oid, void *);
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void for_each_alternate_ref(alternate_ref_fn, void *);
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/*
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* Add the directory to the on-disk alternates file; the new entry will also
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* take effect in the current process.
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*/
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void add_to_alternates_file(const char *dir);
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/*
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* Add the directory to the in-memory list of alternates (along with any
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* recursive alternates it points to), but do not modify the on-disk alternates
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* file.
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*/
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void add_to_alternates_memory(const char *dir);
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/*
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* Populate and return the loose object cache array corresponding to the
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* given object ID.
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*/
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struct oid_array *odb_loose_cache(struct object_directory *odb,
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const struct object_id *oid);
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/* Empty the loose object cache for the specified object directory. */
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void odb_clear_loose_cache(struct object_directory *odb);
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struct packed_git {
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struct hashmap_entry packmap_ent;
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struct packed_git *next;
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struct list_head mru;
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struct pack_window *windows;
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off_t pack_size;
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const void *index_data;
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size_t index_size;
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uint32_t num_objects;
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uint32_t num_bad_objects;
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unsigned char *bad_object_sha1;
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int index_version;
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time_t mtime;
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int pack_fd;
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int index; /* for builtin/pack-objects.c */
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unsigned pack_local:1,
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pack_keep:1,
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pack_keep_in_core:1,
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freshened:1,
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do_not_close:1,
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pack_promisor:1,
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multi_pack_index:1;
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unsigned char hash[GIT_MAX_RAWSZ];
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struct revindex_entry *revindex;
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/* something like ".git/objects/pack/xxxxx.pack" */
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char pack_name[FLEX_ARRAY]; /* more */
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};
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struct multi_pack_index;
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static inline int pack_map_entry_cmp(const void *unused_cmp_data,
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const struct hashmap_entry *entry,
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const struct hashmap_entry *entry2,
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const void *keydata)
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{
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const char *key = keydata;
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const struct packed_git *pg1, *pg2;
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pg1 = container_of(entry, const struct packed_git, packmap_ent);
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pg2 = container_of(entry2, const struct packed_git, packmap_ent);
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return strcmp(pg1->pack_name, key ? key : pg2->pack_name);
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}
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struct raw_object_store {
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/*
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* Set of all object directories; the main directory is first (and
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* cannot be NULL after initialization). Subsequent directories are
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* alternates.
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*/
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struct object_directory *odb;
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struct object_directory **odb_tail;
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int loaded_alternates;
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/*
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* A list of alternate object directories loaded from the environment;
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* this should not generally need to be accessed directly, but will
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* populate the "odb" list when prepare_alt_odb() is run.
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*/
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char *alternate_db;
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/*
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* Objects that should be substituted by other objects
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* (see git-replace(1)).
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*/
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struct oidmap *replace_map;
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unsigned replace_map_initialized : 1;
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pthread_mutex_t replace_mutex; /* protect object replace functions */
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struct commit_graph *commit_graph;
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unsigned commit_graph_attempted : 1; /* if loading has been attempted */
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/*
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* private data
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*
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* should only be accessed directly by packfile.c and midx.c
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*/
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struct multi_pack_index *multi_pack_index;
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/*
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* private data
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*
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* should only be accessed directly by packfile.c
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*/
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struct packed_git *packed_git;
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/* A most-recently-used ordered version of the packed_git list. */
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struct list_head packed_git_mru;
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/*
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* A map of packfiles to packed_git structs for tracking which
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* packs have been loaded already.
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*/
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struct hashmap pack_map;
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/*
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* A fast, rough count of the number of objects in the repository.
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* These two fields are not meant for direct access. Use
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* approximate_object_count() instead.
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*/
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unsigned long approximate_object_count;
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unsigned approximate_object_count_valid : 1;
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/*
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* Whether packed_git has already been populated with this repository's
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* packs.
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*/
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unsigned packed_git_initialized : 1;
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};
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struct raw_object_store *raw_object_store_new(void);
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void raw_object_store_clear(struct raw_object_store *o);
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/*
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* Put in `buf` the name of the file in the local object database that
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* would be used to store a loose object with the specified oid.
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*/
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const char *loose_object_path(struct repository *r, struct strbuf *buf,
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const struct object_id *oid);
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void *map_loose_object(struct repository *r, const struct object_id *oid,
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unsigned long *size);
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void *read_object_file_extended(struct repository *r,
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const struct object_id *oid,
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enum object_type *type,
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unsigned long *size, int lookup_replace);
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static inline void *repo_read_object_file(struct repository *r,
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const struct object_id *oid,
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enum object_type *type,
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unsigned long *size)
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{
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return read_object_file_extended(r, oid, type, size, 1);
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}
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#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
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#define read_object_file(oid, type, size) repo_read_object_file(the_repository, oid, type, size)
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#endif
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/* Read and unpack an object file into memory, write memory to an object file */
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int oid_object_info(struct repository *r, const struct object_id *, unsigned long *);
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int hash_object_file(const void *buf, unsigned long len,
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const char *type, struct object_id *oid);
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int write_object_file(const void *buf, unsigned long len,
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const char *type, struct object_id *oid);
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int hash_object_file_literally(const void *buf, unsigned long len,
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const char *type, struct object_id *oid,
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unsigned flags);
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int pretend_object_file(void *, unsigned long, enum object_type,
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struct object_id *oid);
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int force_object_loose(const struct object_id *oid, time_t mtime);
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/*
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* Open the loose object at path, check its hash, and return the contents,
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* type, and size. If the object is a blob, then "contents" may return NULL,
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* to allow streaming of large blobs.
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*
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* Returns 0 on success, negative on error (details may be written to stderr).
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*/
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int read_loose_object(const char *path,
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const struct object_id *expected_oid,
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enum object_type *type,
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unsigned long *size,
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void **contents);
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#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
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#define has_sha1_file_with_flags(sha1, flags) repo_has_sha1_file_with_flags(the_repository, sha1, flags)
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#define has_sha1_file(sha1) repo_has_sha1_file(the_repository, sha1)
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#endif
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/* Same as the above, except for struct object_id. */
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int repo_has_object_file(struct repository *r, const struct object_id *oid);
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int repo_has_object_file_with_flags(struct repository *r,
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const struct object_id *oid, int flags);
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#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
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#define has_object_file(oid) repo_has_object_file(the_repository, oid)
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#define has_object_file_with_flags(oid, flags) repo_has_object_file_with_flags(the_repository, oid, flags)
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#endif
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/*
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* Return true iff an alternate object database has a loose object
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* with the specified name. This function does not respect replace
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* references.
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*/
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int has_loose_object_nonlocal(const struct object_id *);
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void assert_oid_type(const struct object_id *oid, enum object_type expect);
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struct object_info {
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/* Request */
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enum object_type *typep;
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unsigned long *sizep;
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off_t *disk_sizep;
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unsigned char *delta_base_sha1;
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struct strbuf *type_name;
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void **contentp;
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/* Response */
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enum {
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OI_CACHED,
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OI_LOOSE,
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OI_PACKED,
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OI_DBCACHED
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} whence;
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union {
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/*
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* struct {
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* ... Nothing to expose in this case
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* } cached;
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* struct {
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* ... Nothing to expose in this case
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* } loose;
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*/
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struct {
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struct packed_git *pack;
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off_t offset;
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unsigned int is_delta;
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} packed;
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} u;
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};
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/*
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* Initializer for a "struct object_info" that wants no items. You may
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* also memset() the memory to all-zeroes.
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*/
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#define OBJECT_INFO_INIT {NULL}
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/* Invoke lookup_replace_object() on the given hash */
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#define OBJECT_INFO_LOOKUP_REPLACE 1
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/* Allow reading from a loose object file of unknown/bogus type */
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#define OBJECT_INFO_ALLOW_UNKNOWN_TYPE 2
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/* Do not check cached storage */
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#define OBJECT_INFO_SKIP_CACHED 4
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/* Do not retry packed storage after checking packed and loose storage */
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#define OBJECT_INFO_QUICK 8
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/* Do not check loose object */
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#define OBJECT_INFO_IGNORE_LOOSE 16
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/*
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* Do not attempt to fetch the object if missing (even if fetch_is_missing is
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* nonzero).
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*/
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#define OBJECT_INFO_SKIP_FETCH_OBJECT 32
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/*
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* This is meant for bulk prefetching of missing blobs in a partial
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* clone. Implies OBJECT_INFO_SKIP_FETCH_OBJECT and OBJECT_INFO_QUICK
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*/
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#define OBJECT_INFO_FOR_PREFETCH (OBJECT_INFO_SKIP_FETCH_OBJECT | OBJECT_INFO_QUICK)
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int oid_object_info_extended(struct repository *r,
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const struct object_id *,
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struct object_info *, unsigned flags);
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/*
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* Iterate over the files in the loose-object parts of the object
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* directory "path", triggering the following callbacks:
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*
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* - loose_object is called for each loose object we find.
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*
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* - loose_cruft is called for any files that do not appear to be
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* loose objects. Note that we only look in the loose object
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* directories "objects/[0-9a-f]{2}/", so we will not report
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* "objects/foobar" as cruft.
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*
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* - loose_subdir is called for each top-level hashed subdirectory
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* of the object directory (e.g., "$OBJDIR/f0"). It is called
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* after the objects in the directory are processed.
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*
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* Any callback that is NULL will be ignored. Callbacks returning non-zero
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* will end the iteration.
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*
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* In the "buf" variant, "path" is a strbuf which will also be used as a
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* scratch buffer, but restored to its original contents before
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* the function returns.
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*/
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typedef int each_loose_object_fn(const struct object_id *oid,
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const char *path,
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void *data);
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typedef int each_loose_cruft_fn(const char *basename,
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const char *path,
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void *data);
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typedef int each_loose_subdir_fn(unsigned int nr,
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const char *path,
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void *data);
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int for_each_file_in_obj_subdir(unsigned int subdir_nr,
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struct strbuf *path,
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each_loose_object_fn obj_cb,
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each_loose_cruft_fn cruft_cb,
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each_loose_subdir_fn subdir_cb,
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void *data);
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int for_each_loose_file_in_objdir(const char *path,
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each_loose_object_fn obj_cb,
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each_loose_cruft_fn cruft_cb,
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each_loose_subdir_fn subdir_cb,
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void *data);
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int for_each_loose_file_in_objdir_buf(struct strbuf *path,
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each_loose_object_fn obj_cb,
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each_loose_cruft_fn cruft_cb,
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each_loose_subdir_fn subdir_cb,
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void *data);
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/* Flags for for_each_*_object() below. */
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enum for_each_object_flags {
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/* Iterate only over local objects, not alternates. */
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FOR_EACH_OBJECT_LOCAL_ONLY = (1<<0),
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/* Only iterate over packs obtained from the promisor remote. */
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FOR_EACH_OBJECT_PROMISOR_ONLY = (1<<1),
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/*
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* Visit objects within a pack in packfile order rather than .idx order
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*/
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FOR_EACH_OBJECT_PACK_ORDER = (1<<2),
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};
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/*
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* Iterate over all accessible loose objects without respect to
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* reachability. By default, this includes both local and alternate objects.
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* The order in which objects are visited is unspecified.
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*
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* Any flags specific to packs are ignored.
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*/
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int for_each_loose_object(each_loose_object_fn, void *,
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enum for_each_object_flags flags);
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/*
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* Iterate over all accessible packed objects without respect to reachability.
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* By default, this includes both local and alternate packs.
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*
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* Note that some objects may appear twice if they are found in multiple packs.
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* Each pack is visited in an unspecified order. By default, objects within a
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* pack are visited in pack-idx order (i.e., sorted by oid).
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*/
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typedef int each_packed_object_fn(const struct object_id *oid,
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struct packed_git *pack,
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uint32_t pos,
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void *data);
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int for_each_object_in_pack(struct packed_git *p,
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each_packed_object_fn, void *data,
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enum for_each_object_flags flags);
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int for_each_packed_object(each_packed_object_fn, void *,
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enum for_each_object_flags flags);
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#endif /* OBJECT_STORE_H */
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