Add a in-memory cache

This is a more general API that caches data with a LRU scheme. See
include/cache.h. No comments yet, I'm still working on it. But Jeremy has given
me a hint in one of his checkins that he would like to make use of this now.

The idea is that we get rid of all our silly little caches and merge them all
into one cache that we can then very easily trim, for example even with a
smbcontrol message if someone decides memory is tight. The main user is the
stat cache, this patch also converts the getwd cache. More caches to come.
(This used to be commit 7a911b35713538d82001a3c9f34152e293fe1943)

1 files changed, 23 insertions, 41 deletions

diff --git a/source3/smbd/statcache.c b/source3/smbd/statcache.c
index 8f1e008985..72fed008a2 100644
--- a/source3/smbd/statcache.c
+++ b/source3/smbd/statcache.c
@@ -26,8 +26,6 @@
  Stat cache code used in unix_convert.
 *****************************************************************************/
 
-static TDB_CONTEXT *tdb_stat_cache;
-
 /**
  * Add an entry into the stat cache.
  *
@@ -45,10 +43,8 @@ void stat_cache_add( const char *full_orig_name,
 		bool case_sensitive)
 {
 	size_t translated_path_length;
-	TDB_DATA data_val;
 	char *original_path;
 	size_t original_path_length;
-	size_t sc_size = lp_max_stat_cache_size();
 	char saved_char;
 	TALLOC_CTX *ctx = talloc_tos();
 
@@ -56,12 +52,6 @@ void stat_cache_add( const char *full_orig_name,
 		return;
 	}
 
-	if (sc_size && (tdb_map_size(tdb_stat_cache) > sc_size*1024)) {
-		reset_stat_cache();
-	}
-
-	ZERO_STRUCT(data_val);
-
 	/*
 	 * Don't cache trivial valid directory entries such as . and ..
 	 */
@@ -132,24 +122,20 @@ void stat_cache_add( const char *full_orig_name,
 	saved_char = translated_path[translated_path_length];
 	translated_path[translated_path_length] = '\0';
 
-	data_val.dsize = translated_path_length + 1;
-	data_val.dptr = (uint8 *)translated_path;
-
 	/*
 	 * New entry or replace old entry.
 	 */
 
-	if (tdb_store_bystring(tdb_stat_cache, original_path, data_val,
-				TDB_REPLACE) != 0) {
-		DEBUG(0,("stat_cache_add: Error storing entry %s -> %s\n",
-					original_path, translated_path));
-	} else {
-		DEBUG(5,("stat_cache_add: Added entry (%lx:size%x) %s -> %s\n",
-			(unsigned long)data_val.dptr,
-			(unsigned int)data_val.dsize,
-			original_path,
-			translated_path));
-	}
+	memcache_add(
+		smbd_memcache(), STAT_CACHE,
+		data_blob_const(original_path, original_path_length),
+		data_blob_const(translated_path, translated_path_length + 1));
+
+	DEBUG(5,("stat_cache_add: Added entry (%lx:size %x) %s -> %s\n",
+		 (unsigned long)translated_path,
+		 (unsigned int)translated_path_length,
+		 original_path,
+		 translated_path));
 
 	translated_path[translated_path_length] = saved_char;
 	TALLOC_FREE(original_path);
@@ -186,7 +172,7 @@ bool stat_cache_lookup(connection_struct *conn,
 	unsigned int num_components = 0;
 	char *translated_path;
 	size_t translated_path_length;
-	TDB_DATA data_val;
+	DATA_BLOB data_val;
 	char *name;
 	TALLOC_CTX *ctx = talloc_tos();
 
@@ -236,9 +222,12 @@ bool stat_cache_lookup(connection_struct *conn,
 	while (1) {
 		char *sp;
 
-		data_val = tdb_fetch_bystring(tdb_stat_cache, chk_name);
+		data_val = data_blob_null;
 
-		if (data_val.dptr != NULL && data_val.dsize != 0) {
+		if (memcache_lookup(
+			    smbd_memcache(), STAT_CACHE,
+			    data_blob_const(chk_name, strlen(chk_name)),
+			    &data_val)) {
 			break;
 		}
 
@@ -275,12 +264,11 @@ bool stat_cache_lookup(connection_struct *conn,
 		}
 	}
 
-	translated_path = talloc_strdup(ctx,(char *)data_val.dptr);
+	translated_path = talloc_strdup(ctx,(char *)data_val.data);
 	if (!translated_path) {
 		smb_panic("talloc failed");
 	}
-	translated_path_length = data_val.dsize - 1;
-	SAFE_FREE(data_val.dptr);
+	translated_path_length = data_val.length - 1;
 
 	DEBUG(10,("stat_cache_lookup: lookup succeeded for name [%s] "
 		  "-> [%s]\n", chk_name, translated_path ));
@@ -288,7 +276,8 @@ bool stat_cache_lookup(connection_struct *conn,
 
 	if (SMB_VFS_STAT(conn, translated_path, pst) != 0) {
 		/* Discard this entry - it doesn't exist in the filesystem. */
-		tdb_delete_bystring(tdb_stat_cache, chk_name);
+		memcache_delete(smbd_memcache(), STAT_CACHE,
+				data_blob_const(chk_name, strlen(chk_name)));
 		TALLOC_FREE(chk_name);
 		TALLOC_FREE(translated_path);
 		return False;
@@ -366,7 +355,8 @@ void stat_cache_delete(const char *name)
 	DEBUG(10,("stat_cache_delete: deleting name [%s] -> %s\n",
 			lname, name ));
 
-	tdb_delete_bystring(tdb_stat_cache, lname);
+	memcache_delete(smbd_memcache(), STAT_CACHE,
+			data_blob_const(lname, talloc_get_size(lname)-1));
 	TALLOC_FREE(lname);
 }
 
@@ -395,15 +385,7 @@ bool reset_stat_cache( void )
 	if (!lp_stat_cache())
 		return True;
 
-	if (tdb_stat_cache) {
-		tdb_close(tdb_stat_cache);
-	}
+	memcache_flush(smbd_memcache(), STAT_CACHE);
 
-	/* Create the in-memory tdb using our custom hash function. */
-	tdb_stat_cache = tdb_open_ex("statcache", 1031, TDB_INTERNAL,
-				(O_RDWR|O_CREAT), 0644, NULL, fast_string_hash);
-
-	if (!tdb_stat_cache)
-		return False;
 	return True;
 }