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commit_packed_refs(): use a staging file separate from the lockfile

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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>
This commit is contained in:
Michael Haggerty 2017-06-23 09:01:40 +02:00 committed by Junio C Hamano
parent 3478983b51
commit 42dfa7ecef
1 changed files with 32 additions and 8 deletions
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40
refs/packed-backend.c
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@ -68,6 +68,13 @@ struct packed_ref_store {
* thus the enclosing `packed_ref_store`) must not be freed. * thus the enclosing `packed_ref_store`) must not be freed.
*/ */
struct lock_file lock; 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, 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; 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( if (hold_lock_file_for_update_timeout(
&refs->lock, &refs->lock,
refs->path, refs->path,
flags, timeout_value) < 0) flags, timeout_value) < 0 ||
close_lock_file(&refs->lock))
return -1; return -1;
/* /*
@ -567,13 +580,23 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
get_packed_ref_cache(refs); get_packed_ref_cache(refs);
int ok; int ok;
int ret = -1; int ret = -1;
struct strbuf sb = STRBUF_INIT;
FILE *out; FILE *out;
struct ref_iterator *iter; struct ref_iterator *iter;
if (!is_lock_file_locked(&refs->lock)) if (!is_lock_file_locked(&refs->lock))
die("BUG: commit_packed_refs() called when unlocked"); 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) { if (!out) {
strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s", strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s",
strerror(errno)); 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) { if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0) {
strbuf_addf(err, "error writing to %s: %s", 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; 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, if (write_packed_entry(out, iter->refname, iter->oid->hash,
peel_error ? NULL : peeled.hash)) { peel_error ? NULL : peeled.hash)) {
strbuf_addf(err, "error writing to %s: %s", strbuf_addf(err, "error writing to %s: %s",
get_lock_file_path(&refs->lock), get_tempfile_path(&refs->tempfile),
strerror(errno)); strerror(errno));
ref_iterator_abort(iter); ref_iterator_abort(iter);
goto error; goto error;
@ -602,13 +625,13 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
} }
if (ok != ITER_DONE) { 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"); "error iterating over old contents");
goto error; goto error;
} }
if (commit_lock_file(&refs->lock)) { if (rename_tempfile(&refs->tempfile, refs->path)) {
strbuf_addf(err, "error overwriting %s: %s", strbuf_addf(err, "error replacing %s: %s",
refs->path, strerror(errno)); refs->path, strerror(errno));
goto out; goto out;
} }
@ -617,9 +640,10 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
goto out; goto out;
error: error:
rollback_lock_file(&refs->lock); delete_tempfile(&refs->tempfile);
out: out:
rollback_lock_file(&refs->lock);
release_packed_ref_cache(packed_ref_cache); release_packed_ref_cache(packed_ref_cache);
return ret; return ret;
} }