Mercurial > dovecot > original-hg > dovecot-1.2

changeset 7138:876c7bca351c HEAD

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Link cache records together directly when writing the new records, instead of delaying them until later and causing lots of small writes. We still do this delayed check and do the writes when it's required, but it shouldn't happen normally.
author Timo Sirainen <tss@iki.fi>
date Thu, 10 Jan 2008 04:23:23 +0200
parents c33c87781ab4
children 7424de4bac23
files src/lib-index/mail-cache-lookup.c src/lib-index/mail-cache-private.h src/lib-index/mail-cache-transaction.c
diffstat 3 files changed, 59 insertions(+), 14 deletions(-) [+]
line wrap: on
line diff
--- a/src/lib-index/mail-cache-lookup.c	Mon Jan 07 12:49:40 2008 +0200
+++ b/src/lib-index/mail-cache-lookup.c	Thu Jan 10 04:23:23 2008 +0200
@@ -48,24 +48,39 @@
 	return 0;
 }
 
+uint32_t mail_cache_lookup_cur_offset(struct mail_index_view *view,
+				      uint32_t seq, uint32_t *reset_id_r)
+{
+	struct mail_cache *cache = mail_index_view_get_index(view)->cache;
+	struct mail_index_map *map;
+	const void *data;
+	uint32_t offset;
+
+	mail_index_lookup_ext_full(view, seq, cache->ext_id,
+				   &map, &data, NULL);
+	if (data == NULL) {
+		/* no cache offsets */
+		return 0;
+	}
+	offset = *((const uint32_t *)data);
+	if (offset == 0)
+		return 0;
+
+	if (!mail_index_ext_get_reset_id(view, map, cache->ext_id, reset_id_r))
+		i_unreached();
+	return offset;
+}
+
 static int
 mail_cache_lookup_offset(struct mail_cache *cache, struct mail_index_view *view,
 			 uint32_t seq, uint32_t *offset_r)
 {
-	struct mail_index_map *map;
-	const void *data;
-	uint32_t reset_id;
+	uint32_t offset, reset_id;
 	int i, ret;
 
-	mail_index_lookup_ext_full(view, seq, cache->ext_id,
-				   &map, &data, NULL);
-	if (data == NULL || *((const uint32_t *)data) == 0) {
-		/* nothing in cache (for this record) */
+	offset = mail_cache_lookup_cur_offset(view, seq, &reset_id);
+	if (offset == 0)
 		return 0;
-	}
-
-	if (!mail_index_ext_get_reset_id(view, map, cache->ext_id, &reset_id))
-		i_unreached();
 
 	/* reset_id must match file_seq or the offset is for a different cache
 	   file. if this happens, try if reopening the cache helps. if not,
@@ -86,7 +101,7 @@
 		}
 	}
 
-	*offset_r = *((const uint32_t *)data);
+	*offset_r = offset;
 	return 1;
 }
 
--- a/src/lib-index/mail-cache-private.h	Mon Jan 07 12:49:40 2008 +0200
+++ b/src/lib-index/mail-cache-private.h	Thu Jan 10 04:23:23 2008 +0200
@@ -230,6 +230,8 @@
 int mail_cache_header_fields_get_next_offset(struct mail_cache *cache,
 					     uint32_t *offset_r);
 
+uint32_t mail_cache_lookup_cur_offset(struct mail_index_view *view,
+				      uint32_t seq, uint32_t *reset_id_r);
 int mail_cache_get_record(struct mail_cache *cache, uint32_t offset,
 			  const struct mail_cache_record **rec_r);
 uint32_t mail_cache_get_first_new_seq(struct mail_index_view *view);
--- a/src/lib-index/mail-cache-transaction.c	Mon Jan 07 12:49:40 2008 +0200
+++ b/src/lib-index/mail-cache-transaction.c	Thu Jan 10 04:23:23 2008 +0200
@@ -673,6 +673,7 @@
 	struct mail_cache_record *rec, new_rec;
 	void *data;
 	size_t size;
+	uint32_t reset_id;
 
 	if (ctx->prev_seq != 0) {
 		/* fix record size */
@@ -681,6 +682,15 @@
 		rec->size = size - ctx->prev_pos;
 		i_assert(rec->size > sizeof(*rec));
 
+		/* set prev_offset if possible */
+		rec->prev_offset =
+			mail_cache_lookup_cur_offset(ctx->view->view,
+						     ctx->prev_seq, &reset_id);
+		if (reset_id != ctx->cache->hdr->file_seq)
+			rec->prev_offset = 0;
+		else
+			ctx->cache->hdr_copy.continued_record_count++;
+
 		array_append(&ctx->cache_data_seq, &ctx->prev_seq, 1);
 		ctx->prev_pos = size;
 	} else if (ctx->cache_data == NULL) {
@@ -1025,18 +1035,36 @@
 int mail_cache_link(struct mail_cache *cache, uint32_t old_offset,
 		    uint32_t new_offset)
 {
+	const struct mail_cache_record *rec;
+
 	i_assert(cache->locked);
 
 	if (MAIL_CACHE_IS_UNUSABLE(cache))
 		return -1;
 
-	if (new_offset + sizeof(struct mail_cache_record) >
-	    cache->hdr_copy.used_file_size) {
+	/* this function is called for each added cache record (or cache
+	   extension record update actually) with new_offset pointing to the
+	   new record and old_offset pointing to the previous record.
+
+	   we want to keep the old and new records linked so both old and new
+	   cached data is found. normally they are already linked correctly.
+	   the problem only comes when multiple processes are adding cache
+	   records at the same time. we'd rather not lose those additions, so
+	   force the linking order to be new_offset -> old_offset if it isn't
+	   already. */
+	if (mail_cache_map(cache, new_offset, sizeof(*rec)) < 0)
+		return -1;
+	if (new_offset + sizeof(*rec) > cache->mmap_length) {
 		mail_cache_set_corrupted(cache,
 			"Cache record offset %u points outside file",
 			new_offset);
 		return -1;
 	}
+	rec = CACHE_RECORD(cache, new_offset);
+	if (rec->prev_offset == old_offset) {
+		/* link is already correct */
+		return 0;
+	}
 
 	if (mail_cache_link_unlocked(cache, old_offset, new_offset) < 0)
 		return -1;