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[PATCH v3 12/12] refs: do not invalidate the packed-refs cache unnecessarily

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Jun 20, 2013, 08:37 UTC
Message-ID
<1371717474-28942-13-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1371717474-28942-1-git-send-email-mhagger@alum.mit.edu>

Now that we keep track of the packed-refs file metadata, we can detect when the packed-refs file has been modified since we last read it, and we do so automatically every time that get_packed_ref_cache() is called. So there is no need to invalidate the cache automatically when lock_packed_refs() is called; usually the old copy will still be valid.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/refs.c b/refs.c
index 787cc1c..038e5c7 100644
--- a/refs.c
+++ b/refs.c
@@ -2136,11 +2136,14 @@ int lock_packed_refs(int flags)
 {
 	struct packed_ref_cache *packed_ref_cache;
 
-	/* Discard the old cache because it might be invalid: */
-	clear_packed_ref_cache(&ref_cache);
 	if (hold_lock_file_for_update(&packlock, git_path("packed-refs"), flags) < 0)
 		return -1;
-	/* Read the current packed-refs while holding the lock: */
+	/*
+	 * Get the current packed-refs while holding the lock.  If the
+	 * packed-refs file has been modified since we last read it,
+	 * this will automatically invalidate the cache and re-read
+	 * the packed-refs file.
+	 */
 	packed_ref_cache = get_packed_ref_cache(&ref_cache);
 	packed_ref_cache->lock = &packlock;
 	/* Increment the reference count to prevent it from being freed: */
-- 
1.8.3.1
Previous: Michael Haggerty
Message 13 of 13 in “Fix some reference-related races”
  1. 00/12 Fix some reference-related racesMichael Haggerty, Jun 20, 2013
  2. 01/12 repack_without_ref(): split list curation and entry writingMichael Haggerty, Jun 20, 2013
  3. 02/12 pack_refs(): split creation of packed refs and entry writingMichael Haggerty, Jun 20, 2013
  4. 03/12 refs: wrap the packed refs cache in a level of indirectionMichael Haggerty, Jun 20, 2013
  5. 04/12 refs: implement simple transactions for the packed-refs fileMichael Haggerty, Jun 20, 2013
  6. 05/12 refs: manage lifetime of packed refs cache via reference countingMichael Haggerty, Jun 20, 2013
  7. 06/12 do_for_each_entry(): increment the packed refs cache refcountMichael Haggerty, Jun 20, 2013
  8. 07/12 packed_ref_cache: increment refcount when lockedMichael Haggerty, Jun 20, 2013
  9. 08/12 Extract a struct stat_data from cache_entryMichael Haggerty, Jun 20, 2013
  10. 09/12 add a stat_validity structMichael Haggerty, Jun 20, 2013
  11. 10/12 get_packed_ref_cache: reload packed-refs file when it changesMichael Haggerty, Jun 20, 2013
  12. 11/12 for_each_ref: load all loose refs before packed refsMichael Haggerty, Jun 20, 2013
  13. 12/12 refs: do not invalidate the packed-refs cache unnecessarilyMichael Haggerty, Jun 20, 2013

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