diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt index 9a3ad71e9e..3ab3810c86 100644 --- a/Documentation/config/core.txt +++ b/Documentation/config/core.txt @@ -595,6 +595,14 @@ core.fsyncMethod:: * `writeout-only` issues pagecache writeback requests, but depending on the filesystem and storage hardware, data added to the repository may not be durable in the event of a system crash. This is the default mode on macOS. +* `batch` enables a mode that uses writeout-only flushes to stage multiple + updates in the disk writeback cache and then does a single full fsync of + a dummy file to trigger the disk cache flush at the end of the operation. ++ +Currently `batch` mode only applies to loose-object files. Other repository +data is made durable as if `fsync` was specified. This mode is expected to +be as safe as `fsync` on macOS for repos stored on HFS+ or APFS filesystems +and on Windows for repos stored on NTFS or ReFS filesystems. core.fsyncObjectFiles:: This boolean will enable 'fsync()' when writing object files. diff --git a/bulk-checkin.c b/bulk-checkin.c index ad855267d2..df451bdf42 100644 --- a/bulk-checkin.c +++ b/bulk-checkin.c @@ -3,15 +3,20 @@ */ #include "cache.h" #include "bulk-checkin.h" +#include "lockfile.h" #include "repository.h" #include "csum-file.h" #include "pack.h" #include "strbuf.h" +#include "string-list.h" +#include "tmp-objdir.h" #include "packfile.h" #include "object-store.h" static int odb_transaction_nesting; +static struct tmp_objdir *bulk_fsync_objdir; + static struct bulk_checkin_packfile { char *pack_tmp_name; struct hashfile *f; @@ -80,6 +85,40 @@ clear_exit: reprepare_packed_git(the_repository); } +/* + * Cleanup after batch-mode fsync_object_files. + */ +static void flush_batch_fsync(void) +{ + struct strbuf temp_path = STRBUF_INIT; + struct tempfile *temp; + + if (!bulk_fsync_objdir) + return; + + /* + * Issue a full hardware flush against a temporary file to ensure + * that all objects are durable before any renames occur. The code in + * fsync_loose_object_bulk_checkin has already issued a writeout + * request, but it has not flushed any writeback cache in the storage + * hardware or any filesystem logs. This fsync call acts as a barrier + * to ensure that the data in each new object file is durable before + * the final name is visible. + */ + strbuf_addf(&temp_path, "%s/bulk_fsync_XXXXXX", get_object_directory()); + temp = xmks_tempfile(temp_path.buf); + fsync_or_die(get_tempfile_fd(temp), get_tempfile_path(temp)); + delete_tempfile(&temp); + strbuf_release(&temp_path); + + /* + * Make the object files visible in the primary ODB after their data is + * fully durable. + */ + tmp_objdir_migrate(bulk_fsync_objdir); + bulk_fsync_objdir = NULL; +} + static int already_written(struct bulk_checkin_packfile *state, struct object_id *oid) { int i; @@ -274,6 +313,37 @@ static int deflate_to_pack(struct bulk_checkin_packfile *state, return 0; } +void prepare_loose_object_bulk_checkin(void) +{ + /* + * We lazily create the temporary object directory + * the first time an object might be added, since + * callers may not know whether any objects will be + * added at the time they call begin_odb_transaction. + */ + if (!odb_transaction_nesting || bulk_fsync_objdir) + return; + + bulk_fsync_objdir = tmp_objdir_create("bulk-fsync"); + if (bulk_fsync_objdir) + tmp_objdir_replace_primary_odb(bulk_fsync_objdir, 0); +} + +void fsync_loose_object_bulk_checkin(int fd, const char *filename) +{ + /* + * If we have an active ODB transaction, we issue a call that + * cleans the filesystem page cache but avoids a hardware flush + * command. Later on we will issue a single hardware flush + * before renaming the objects to their final names as part of + * flush_batch_fsync. + */ + if (!bulk_fsync_objdir || + git_fsync(fd, FSYNC_WRITEOUT_ONLY) < 0) { + fsync_or_die(fd, filename); + } +} + int index_bulk_checkin(struct object_id *oid, int fd, size_t size, enum object_type type, const char *path, unsigned flags) @@ -292,6 +362,7 @@ void begin_odb_transaction(void) void flush_odb_transaction(void) { + flush_batch_fsync(); flush_bulk_checkin_packfile(&bulk_checkin_packfile); } diff --git a/bulk-checkin.h b/bulk-checkin.h index ee0832989a..8281b9cb15 100644 --- a/bulk-checkin.h +++ b/bulk-checkin.h @@ -6,6 +6,9 @@ #include "cache.h" +void prepare_loose_object_bulk_checkin(void); +void fsync_loose_object_bulk_checkin(int fd, const char *filename); + int index_bulk_checkin(struct object_id *oid, int fd, size_t size, enum object_type type, const char *path, unsigned flags); diff --git a/cache.h b/cache.h index 3ba96dbd77..ca0085717d 100644 --- a/cache.h +++ b/cache.h @@ -1037,7 +1037,8 @@ extern int use_fsync; enum fsync_method { FSYNC_METHOD_FSYNC, - FSYNC_METHOD_WRITEOUT_ONLY + FSYNC_METHOD_WRITEOUT_ONLY, + FSYNC_METHOD_BATCH, }; extern enum fsync_method fsync_method; @@ -1750,6 +1751,11 @@ void fsync_or_die(int fd, const char *); int fsync_component(enum fsync_component component, int fd); void fsync_component_or_die(enum fsync_component component, int fd, const char *msg); +static inline int batch_fsync_enabled(enum fsync_component component) +{ + return (fsync_components & component) && (fsync_method == FSYNC_METHOD_BATCH); +} + ssize_t read_in_full(int fd, void *buf, size_t count); ssize_t write_in_full(int fd, const void *buf, size_t count); ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset); diff --git a/config.c b/config.c index 2cde153fe6..6d4caac476 100644 --- a/config.c +++ b/config.c @@ -1687,6 +1687,8 @@ static int git_default_core_config(const char *var, const char *value, void *cb) fsync_method = FSYNC_METHOD_FSYNC; else if (!strcmp(value, "writeout-only")) fsync_method = FSYNC_METHOD_WRITEOUT_ONLY; + else if (!strcmp(value, "batch")) + fsync_method = FSYNC_METHOD_BATCH; else warning(_("ignoring unknown core.fsyncMethod value '%s'"), value); diff --git a/object-file.c b/object-file.c index e3f0bf27ff..a696f5ec69 100644 --- a/object-file.c +++ b/object-file.c @@ -1852,7 +1852,9 @@ static void close_loose_object(int fd) if (the_repository->objects->odb->will_destroy) goto out; - if (fsync_object_files > 0) + if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT)) + fsync_loose_object_bulk_checkin(fd, "loose object file"); + else if (fsync_object_files > 0) fsync_or_die(fd, "loose object file"); else fsync_component_or_die(FSYNC_COMPONENT_LOOSE_OBJECT, fd, @@ -1920,6 +1922,9 @@ static int write_loose_object(const struct object_id *oid, char *hdr, static struct strbuf tmp_file = STRBUF_INIT; static struct strbuf filename = STRBUF_INIT; + if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT)) + prepare_loose_object_bulk_checkin(); + loose_object_path(the_repository, &filename, oid); fd = create_tmpfile(&tmp_file, filename.buf);