[PATCH v2 22/29] commit_packed_refs(): use a staging file separate from the lockfile
- From
Michael Haggerty <mhagger@alum.mit.edu>
- Date
- Jun 23, 2017, 07:01 UTC
- Message-ID
- <d8fa8dec13eb095c0c39ef0de2ee8987d6bf9d77.1498200513.git.mhagger@alum.mit.edu>
- In-Reply-To
- <cover.1498200513.git.mhagger@alum.mit.edu>
We will want to be able to hold the lockfile for `packed-refs` even after we have activated the new values. So use a separate tempfile, `packed-refs.new`, as a place to stage the new contents of the `packed-refs` file. For now this is all done within `commit_packed_refs()`, but that will change shortly.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> --- refs/packed-backend.c | 40 ++++++++++++++++++++++++++++++++-------- 1 file changed, 32 insertions(+), 8 deletions(-)
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 18ce47fcb7..71f92ed6f0 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -68,6 +68,13 @@ struct packed_ref_store { * thus the enclosing `packed_ref_store`) must not be freed. */ struct lock_file lock; + + /* + * Temporary file used when rewriting new contents to the + * "packed-refs" file. Note that this (and thus the enclosing + * `packed_ref_store`) must not be freed. + */ + struct tempfile tempfile; }; struct ref_store *packed_ref_store_create(const char *path, @@ -522,10 +529,16 @@ int lock_packed_refs(struct ref_store *ref_store, int flags) timeout_configured = 1; } + /* + * Note that we close the lockfile immediately because we + * don't write new content to it, but rather to a separate + * tempfile. + */ if (hold_lock_file_for_update_timeout( &refs->lock, refs->path, - flags, timeout_value) < 0) + flags, timeout_value) < 0 || + close_lock_file(&refs->lock)) return -1; /* @@ -567,13 +580,23 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err) get_packed_ref_cache(refs); int ok; int ret = -1; + struct strbuf sb = STRBUF_INIT; FILE *out; struct ref_iterator *iter; if (!is_lock_file_locked(&refs->lock)) die("BUG: commit_packed_refs() called when unlocked"); - out = fdopen_lock_file(&refs->lock, "w"); + strbuf_addf(&sb, "%s.new", refs->path); + if (create_tempfile(&refs->tempfile, sb.buf) < 0) { + strbuf_addf(err, "unable to create file %s: %s", + sb.buf, strerror(errno)); + strbuf_release(&sb); + goto out; + } + strbuf_release(&sb); + + out = fdopen_tempfile(&refs->tempfile, "w"); if (!out) { strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s", strerror(errno)); @@ -582,7 +605,7 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err) if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0) { strbuf_addf(err, "error writing to %s: %s", - get_lock_file_path(&refs->lock), strerror(errno)); + get_tempfile_path(&refs->tempfile), strerror(errno)); goto error; } @@ -594,7 +617,7 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err) if (write_packed_entry(out, iter->refname, iter->oid->hash, peel_error ? NULL : peeled.hash)) { strbuf_addf(err, "error writing to %s: %s", - get_lock_file_path(&refs->lock), + get_tempfile_path(&refs->tempfile), strerror(errno)); ref_iterator_abort(iter); goto error; @@ -602,13 +625,13 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err) } if (ok != ITER_DONE) { - strbuf_addf(err, "unable to write packed-refs file: " + strbuf_addf(err, "unable to rewrite packed-refs file: " "error iterating over old contents"); goto error; } - if (commit_lock_file(&refs->lock)) { - strbuf_addf(err, "error overwriting %s: %s", + if (rename_tempfile(&refs->tempfile, refs->path)) { + strbuf_addf(err, "error replacing %s: %s", refs->path, strerror(errno)); goto out; } @@ -617,9 +640,10 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err) goto out; error: - rollback_lock_file(&refs->lock); + delete_tempfile(&refs->tempfile); out: + rollback_lock_file(&refs->lock); release_packed_ref_cache(packed_ref_cache); return ret; }
-- 2.11.0