get_packed_ref_cache(): assume "packed-refs" won't change while locked
If we've got the "packed-refs" file locked, then it can't change; there's no need to keep calling `stat_validity_check()` on it. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Michael Haggerty committed
May 22, 2017 at 16:17 UTC
28ed9830b1dc65df37bdb3c9b8ef743f1f266262
1 file changed
+11
-5
refs/files-backend.c
+11
-5
@@ -342,13 +342,18 @@ static void files_ref_path(struct files_ref_store *refs,
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/*
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* Get the packed_ref_cache for the specified files_ref_store,
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- * creating it if necessary.
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+ * creating and populating it if it hasn't been read before or if the
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+ * file has been changed (according to its `validity` field) since it
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+ * was last read. On the other hand, if we hold the lock, then assume
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+ * that the file hasn't been changed out from under us, so skip the
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+ * extra `stat()` call in `stat_validity_check()`.
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*/
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static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
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{
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const char *packed_refs_file = files_packed_refs_path(refs);
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if (refs->packed &&
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+ !is_lock_file_locked(&refs->packed_refs_lock) &&
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!stat_validity_check(&refs->packed->validity, packed_refs_file))
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clear_packed_ref_cache(refs);
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@@ -1288,10 +1293,11 @@ static int lock_packed_refs(struct files_ref_store *refs, int flags)
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flags, timeout_value) < 0)
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return -1;
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/*
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- * Get the current packed-refs while holding the lock. If the
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- * packed-refs file has been modified since we last read it,
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- * this will automatically invalidate the cache and re-read
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- * the packed-refs file.
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+ * Get the current packed-refs while holding the lock. It is
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+ * important that we call `get_packed_ref_cache()` before
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+ * setting `packed_ref_cache->lock`, because otherwise the
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+ * former will see that the file is locked and assume that the
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+ * cache can't be stale.
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*/
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packed_ref_cache = get_packed_ref_cache(refs);
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/* Increment the reference count to prevent it from being freed: */