commit_packed_refs(): use a staging file separate from the lockfile
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> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Michael Haggerty committed
Jun 23, 2017 at 09:01 UTC
42dfa7ecef22191b004862fb56074b408c94fc97
1 file changed
+32
-8
refs/packed-backend.c
+32
-8
@@ -68,6 +68,13 @@ struct packed_ref_store {
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* thus the enclosing `packed_ref_store`) must not be freed.
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*/
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struct lock_file lock;
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+
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+ /*
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+ * Temporary file used when rewriting new contents to the
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+ * "packed-refs" file. Note that this (and thus the enclosing
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+ * `packed_ref_store`) must not be freed.
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+ */
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+ struct tempfile tempfile;
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};
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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)
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timeout_configured = 1;
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}
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+ /*
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+ * Note that we close the lockfile immediately because we
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+ * don't write new content to it, but rather to a separate
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+ * tempfile.
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+ */
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if (hold_lock_file_for_update_timeout(
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&refs->lock,
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refs->path,
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- flags, timeout_value) < 0)
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+ flags, timeout_value) < 0 ||
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+ close_lock_file(&refs->lock))
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return -1;
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/*
@@ -567,13 +580,23 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
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get_packed_ref_cache(refs);
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int ok;
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int ret = -1;
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+ struct strbuf sb = STRBUF_INIT;
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FILE *out;
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struct ref_iterator *iter;
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if (!is_lock_file_locked(&refs->lock))
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die("BUG: commit_packed_refs() called when unlocked");
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- out = fdopen_lock_file(&refs->lock, "w");
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+ strbuf_addf(&sb, "%s.new", refs->path);
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+ if (create_tempfile(&refs->tempfile, sb.buf) < 0) {
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+ strbuf_addf(err, "unable to create file %s: %s",
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+ sb.buf, strerror(errno));
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+ strbuf_release(&sb);
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+ goto out;
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+ }
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+ strbuf_release(&sb);
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+
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+ out = fdopen_tempfile(&refs->tempfile, "w");
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if (!out) {
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strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s",
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strerror(errno));
@@ -582,7 +605,7 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
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if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0) {
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strbuf_addf(err, "error writing to %s: %s",
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- get_lock_file_path(&refs->lock), strerror(errno));
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+ get_tempfile_path(&refs->tempfile), strerror(errno));
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goto error;
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}
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@@ -594,7 +617,7 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
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if (write_packed_entry(out, iter->refname, iter->oid->hash,
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peel_error ? NULL : peeled.hash)) {
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strbuf_addf(err, "error writing to %s: %s",
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- get_lock_file_path(&refs->lock),
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+ get_tempfile_path(&refs->tempfile),
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strerror(errno));
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ref_iterator_abort(iter);
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goto error;
@@ -602,13 +625,13 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
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}
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if (ok != ITER_DONE) {
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- strbuf_addf(err, "unable to write packed-refs file: "
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+ strbuf_addf(err, "unable to rewrite packed-refs file: "
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"error iterating over old contents");
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goto error;
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}
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- if (commit_lock_file(&refs->lock)) {
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- strbuf_addf(err, "error overwriting %s: %s",
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+ if (rename_tempfile(&refs->tempfile, refs->path)) {
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+ strbuf_addf(err, "error replacing %s: %s",
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refs->path, strerror(errno));
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goto out;
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}
@@ -617,9 +640,10 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
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goto out;
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error:
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- rollback_lock_file(&refs->lock);
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+ delete_tempfile(&refs->tempfile);
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out:
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+ rollback_lock_file(&refs->lock);
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release_packed_ref_cache(packed_ref_cache);
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return ret;
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}