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[PATCH 02/12] pack_refs(): split creation of packed refs and entry writing

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Jun 11, 2013, 21:48 UTC
Message-ID
<1370987312-6761-3-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1370987312-6761-1-git-send-email-mhagger@alum.mit.edu>
Split pack_refs() into multiple passes:
* Iterate over loose refs.  For each one that can be turned into a
  packed ref, create a corresponding entry in the packed refs cache.
* Write the packed refs to the packed-refs file.

This change isolates the mutation of the packed-refs file to a single place.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 48 ++++++++++++++++++++++++++++++++++--------------
 1 file changed, 34 insertions(+), 14 deletions(-)
diff --git a/refs.c b/refs.c
index dccfe14..bb3640f 100644
--- a/refs.c
+++ b/refs.c
@@ -2019,35 +2019,50 @@ struct ref_to_prune {
 
 struct pack_refs_cb_data {
 	unsigned int flags;
+	struct ref_dir *packed_refs;
 	struct ref_to_prune *ref_to_prune;
-	int fd;
 };
 
-static int pack_one_ref(struct ref_entry *entry, void *cb_data)
+/*
+ * An each_ref_entry_fn that is run over loose references only.  If
+ * the loose reference can be packed, add an entry in the packed ref
+ * cache.  If the reference should be pruned, also add it to
+ * ref_to_prune in the pack_refs_cb_data.
+ */
+static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
 {
 	struct pack_refs_cb_data *cb = cb_data;
 	enum peel_status peel_status;
+	struct ref_entry *packed_entry;
 	int is_tag_ref = !prefixcmp(entry->name, "refs/tags/");
 
-	/* ALWAYS pack refs that were already packed or are tags */
-	if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref &&
-	    !(entry->flag & REF_ISPACKED))
+	/* ALWAYS pack tags */
+	if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
 		return 0;
 
 	/* Do not pack symbolic or broken refs: */
 	if ((entry->flag & REF_ISSYMREF) || !ref_resolves_to_object(entry))
 		return 0;
 
+	/* Add a packed ref cache entry equivalent to the loose entry. */
 	peel_status = peel_entry(entry, 1);
 	if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
 		die("internal error peeling reference %s (%s)",
 		    entry->name, sha1_to_hex(entry->u.value.sha1));
-	write_packed_entry(cb->fd, entry->name, entry->u.value.sha1,
-			   peel_status == PEEL_PEELED ?
-			   entry->u.value.peeled : NULL);
+	packed_entry = find_ref(cb->packed_refs, entry->name);
+	if (packed_entry) {
+		/* Overwrite existing packed entry with info from loose entry */
+		packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
+		hashcpy(packed_entry->u.value.sha1, entry->u.value.sha1);
+	} else {
+		packed_entry = create_ref_entry(entry->name, entry->u.value.sha1,
+						REF_ISPACKED | REF_KNOWS_PEELED, 0);
+		add_ref(cb->packed_refs, packed_entry);
+	}
+	hashcpy(packed_entry->u.value.peeled, entry->u.value.peeled);
 
-	/* If the ref was already packed, there is no need to prune it. */
-	if ((cb->flags & PACK_REFS_PRUNE) && !(entry->flag & REF_ISPACKED)) {
+	/* Schedule the loose reference for pruning if requested. */
+	if ((cb->flags & PACK_REFS_PRUNE)) {
 		int namelen = strlen(entry->name) + 1;
 		struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);
 		hashcpy(n->sha1, entry->u.value.sha1);
@@ -2114,16 +2129,21 @@ static struct lock_file packlock;
 int pack_refs(unsigned int flags)
 {
 	struct pack_refs_cb_data cbdata;
+	int fd;
 
 	memset(&cbdata, 0, sizeof(cbdata));
 	cbdata.flags = flags;
 
-	cbdata.fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"),
-					      LOCK_DIE_ON_ERROR);
+	fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"),
+				       LOCK_DIE_ON_ERROR);
+	cbdata.packed_refs = get_packed_refs(&ref_cache);
 
-	write_or_die(cbdata.fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
+	do_for_each_entry_in_dir(get_loose_refs(&ref_cache), 0,
+				 pack_if_possible_fn, &cbdata);
+
+	write_or_die(fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
+	do_for_each_entry_in_dir(cbdata.packed_refs, 0, write_packed_entry_fn, &fd);
 
-	do_for_each_entry(&ref_cache, "", pack_one_ref, &cbdata);
 	if (commit_lock_file(&packlock) < 0)
 		die_errno("unable to overwrite old ref-pack file");
 	prune_refs(cbdata.ref_to_prune);

-- 
1.8.3
Previous: Michael HaggertyNext: Michael Haggerty
Message 5 of 22 in “Fix some reference-related races”
  1. 00/12 Fix some reference-related racesMichael Haggerty, Jun 11, 2013
  2. 01/12 repack_without_ref(): split list curation and entry writingMichael Haggerty, Jun 11, 2013
  3. Jeff KingJun 12, 2013
  4. Michael HaggertyJun 12, 2013
  5. 02/12 pack_refs(): split creation of packed refs and entry writingMichael Haggerty, Jun 11, 2013
  6. 03/12 refs: wrap the packed refs cache in a level of indirectionMichael Haggerty, Jun 11, 2013
  7. 04/12 refs: implement simple transactions for the packed-refs fileMichael Haggerty, Jun 11, 2013
  8. Jeff KingJun 12, 2013
  9. 05/12 refs: manage lifetime of packed refs cache via reference countingMichael Haggerty, Jun 11, 2013
  10. 06/12 do_for_each_entry(): increment the packed refs cache refcountMichael Haggerty, Jun 11, 2013
  11. 07/12 packed_ref_cache: increment refcount when lockedMichael Haggerty, Jun 11, 2013
  12. 08/12 Extract a struct stat_data from cache_entryMichael Haggerty, Jun 11, 2013
  13. 09/12 add a stat_validity structMichael Haggerty, Jun 11, 2013
  14. 10/12 get_packed_ref_cache: reload packed-refs file when it changesMichael Haggerty, Jun 11, 2013
  15. 11/12 for_each_ref: load all loose refs before packed refsMichael Haggerty, Jun 11, 2013
  16. 12/12 refs: do not invalidate the packed-refs cache unnecessarilyMichael Haggerty, Jun 11, 2013
  17. Jeff KingJun 12, 2013
  18. Jeff KingJun 12, 2013
  19. Ramsay JonesJun 15, 2013
  20. Michael HaggertyJun 16, 2013
  21. Ramsay JonesJun 18, 2013
  22. Michael HaggertyJun 19, 2013

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