r22775: For the cluster code I've developed a wrapper around tdb to put different

database backends in place dynamically.

The main abstractions are db_context and db_record, it should be mainly
self-describing, see include/dbwrap.h.  You open the db just as you would open
a tdb, this time with db_open(). If you want to fetch a record, just do the
db->fetch() call, if you want to do operations on it, you need to get it with
fetch_locked().

I added dbwrap_file.c (not heavily tested lately) as an example for what can
be done with that abstraction, uses a file per key. So if anybody is willing
to shape that up, we might have a chance on reiserfs again.... :-)

This abstraction works fine for brlock.tdb, locking.tdb, connections.tdb and
sessionid.tdb. It should work fine for the others as well, I just did not yet
get around to convert them.

If nobody loudly screams NO, then I will import the code that uses this soon.

Volker

source/lib/dbwrap_file.c

@@ -0,0 +1,413 @@
+/* 
+   Unix SMB/CIFS implementation.
+   Database interface using a file per record
+   Copyright (C) Volker Lendecke 2005
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+ * Be aware that this is just sample code that has not seen too much testing
+ */
+
+#include "includes.h"
+
+struct db_file_ctx {
+	const char *dirname;
+
+	/* We only support one locked record at a time -- everything else
+	 * would lead to a potential deadlock anyway! */
+	struct db_record *locked_record;
+};
+
+struct db_locked_file {
+	int fd;
+	uint8 hash;
+	const char *name;
+	const char *path;
+	struct db_file_ctx *parent;
+};
+
+/* Copy from statcache.c... */
+
+static uint32 fsh(const uint8 *p, int len)
+{
+        uint32 n = 0;
+	int i;
+        for (i=0; i<len; i++) {
+                n = ((n << 5) + n) ^ (uint32)(p[i]);
+        }
+        return n;
+}
+
+static int db_locked_file_destr(struct db_locked_file *data)
+{
+	if (data->parent != NULL) {
+		data->parent->locked_record = NULL;
+	}
+
+	if (close(data->fd) != 0) {
+		DEBUG(3, ("close failed: %s\n", strerror(errno)));
+		return -1;
+	}
+
+	return 0;
+}
+
+static NTSTATUS db_file_store(struct db_record *rec, TDB_DATA data, int flag);
+static NTSTATUS db_file_delete(struct db_record *rec);
+
+static struct db_record *db_file_fetch_locked(struct db_context *db,
+					      TALLOC_CTX *mem_ctx,
+					      TDB_DATA key)
+{
+	struct db_file_ctx *ctx = talloc_get_type_abort(db->private_data,
+							struct db_file_ctx);
+	struct db_record *result;
+	struct db_locked_file *file;
+	struct flock fl;
+	SMB_STRUCT_STAT statbuf;
+	ssize_t nread;
+	int ret;
+
+	SMB_ASSERT(ctx->locked_record == NULL);
+
+ again:
+	if (!(result = TALLOC_P(mem_ctx, struct db_record))) {
+		DEBUG(0, ("talloc failed\n"));
+		return NULL;
+	}
+
+	if (!(file = TALLOC_P(result, struct db_locked_file))) {
+		DEBUG(0, ("talloc failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	result->private_data = file;
+	result->store = db_file_store;
+	result->delete_rec = db_file_delete;
+
+	result->key.dsize = key.dsize;
+	result->key.dptr = (uint8 *)talloc_memdup(result, key.dptr, key.dsize);
+	if (result->key.dptr == NULL) {
+		DEBUG(0, ("talloc failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	/* Cut to 8 bits */
+	file->hash = fsh(key.dptr, key.dsize);
+	file->name = hex_encode(file, (unsigned char *)key.dptr, key.dsize);
+	if (file->name == NULL) {
+		DEBUG(0, ("hex_encode failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	file->path = talloc_asprintf(file, "%s/%2.2X/%s", ctx->dirname,
+				     file->hash, file->name);
+	if (file->path == NULL) {
+		DEBUG(0, ("talloc_asprintf failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	become_root();
+	file->fd = open(file->path, O_RDWR|O_CREAT, 0644);
+	unbecome_root();
+
+	if (file->fd < 0) {
+		DEBUG(3, ("Could not open/create %s: %s\n",
+			  file->path, strerror(errno)));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	talloc_set_destructor(file, db_locked_file_destr);
+
+	fl.l_type = F_WRLCK;
+	fl.l_whence = SEEK_SET;
+	fl.l_start = 0;
+	fl.l_len = 1;
+	fl.l_pid = 0;
+
+	do {
+		ret = fcntl(file->fd, F_SETLKW, &fl);
+	} while ((ret == -1) && (errno == EINTR));
+
+	if (ret == -1) {
+		DEBUG(3, ("Could not get lock on %s: %s\n",
+			  file->path, strerror(errno)));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	if (sys_fstat(file->fd, &statbuf) != 0) {
+		DEBUG(3, ("Could not fstat %s: %s\n",
+			  file->path, strerror(errno)));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	if (statbuf.st_nlink == 0) {
+		/* Someone has deleted it under the lock, retry */
+		TALLOC_FREE(result);
+		goto again;
+	}
+
+	result->value.dsize = 0;
+	result->value.dptr = NULL;
+
+	if (statbuf.st_size != 0) {
+		result->value.dsize = statbuf.st_size;
+		result->value.dptr = TALLOC_ARRAY(result, uint8,
+						  statbuf.st_size);
+		if (result->value.dptr == NULL) {
+			DEBUG(1, ("talloc failed\n"));
+			TALLOC_FREE(result);
+			return NULL;
+		}
+
+		nread = read_data(file->fd, (char *)result->value.dptr,
+				  result->value.dsize);
+		if (nread != result->value.dsize) {
+			DEBUG(3, ("read_data failed: %s\n", strerror(errno)));
+			TALLOC_FREE(result);
+			return NULL;
+		}
+	}
+
+	ctx->locked_record = result;
+	file->parent = (struct db_file_ctx *)talloc_reference(file, ctx);
+
+	return result;
+}
+
+static NTSTATUS db_file_store_root(int fd, TDB_DATA data)
+{
+	if (sys_lseek(fd, 0, SEEK_SET) != 0) {
+		DEBUG(0, ("sys_lseek failed: %s\n", strerror(errno)));
+		return map_nt_error_from_unix(errno);
+	}
+
+	if (write_data(fd, (char *)data.dptr, data.dsize) != data.dsize) {
+		DEBUG(3, ("write_data failed: %s\n", strerror(errno)));
+		return map_nt_error_from_unix(errno);
+	}
+
+	if (sys_ftruncate(fd, data.dsize) != 0) {
+		DEBUG(3, ("sys_ftruncate failed: %s\n", strerror(errno)));
+		return map_nt_error_from_unix(errno);
+	}
+
+	return NT_STATUS_OK;
+}
+
+static NTSTATUS db_file_store(struct db_record *rec, TDB_DATA data, int flag)
+{
+	struct db_locked_file *file =
+		talloc_get_type_abort(rec->private_data,
+				      struct db_locked_file);
+	NTSTATUS status;
+
+	become_root();
+	status = db_file_store_root(file->fd, data);
+	unbecome_root();
+
+	return status;
+}
+
+static NTSTATUS db_file_delete(struct db_record *rec)
+{
+	struct db_locked_file *file =
+		talloc_get_type_abort(rec->private_data,
+				      struct db_locked_file);
+	int res;
+
+	become_root();
+	res = unlink(file->path);
+	unbecome_root();
+
+	if (res == -1) {
+		DEBUG(3, ("unlink(%s) failed: %s\n", file->path,
+			  strerror(errno)));
+		return map_nt_error_from_unix(errno);
+	}
+
+	return NT_STATUS_OK;
+}
+
+static int db_file_traverse(struct db_context *db,
+			    int (*fn)(struct db_record *rec,
+				      void *private_data),
+			    void *private_data)
+{
+	struct db_file_ctx *ctx = talloc_get_type_abort(db->private_data,
+							struct db_file_ctx);
+	TALLOC_CTX *mem_ctx = talloc_init("traversal %s\n", ctx->dirname);
+	
+	int i;
+	int count = 0;
+
+	for (i=0; i<256; i++) {
+		const char *dirname = talloc_asprintf(mem_ctx, "%s/%2.2X",
+						      ctx->dirname, i);
+		DIR *dir;
+		struct dirent *dirent;
+
+		if (dirname == NULL) {
+			DEBUG(0, ("talloc failed\n"));
+			TALLOC_FREE(mem_ctx);
+			return -1;
+		}
+
+		dir = opendir(dirname);
+		if (dir == NULL) {
+			DEBUG(3, ("Could not open dir %s: %s\n", dirname,
+				  strerror(errno)));
+			TALLOC_FREE(mem_ctx);
+			return -1;
+		}
+
+		while ((dirent = readdir(dir)) != NULL) {
+			DATA_BLOB keyblob;
+			TDB_DATA key;
+			struct db_record *rec;
+
+			if ((dirent->d_name[0] == '.') &&
+			    ((dirent->d_name[1] == '\0') ||
+			     ((dirent->d_name[1] == '.') &&
+			      (dirent->d_name[2] == '\0')))) {
+				continue;
+			}
+
+			keyblob = strhex_to_data_blob(mem_ctx, dirent->d_name);
+			if (keyblob.data == NULL) {
+				DEBUG(5, ("strhex_to_data_blob failed\n"));
+				continue;
+			}
+
+			key.dptr = keyblob.data;
+			key.dsize = keyblob.length;
+
+			if ((ctx->locked_record != NULL) &&
+			    (key.dsize == ctx->locked_record->key.dsize) &&
+			    (memcmp(key.dptr, ctx->locked_record->key.dptr,
+				    key.dsize) == 0)) {
+				count += 1;
+				if (fn(ctx->locked_record,
+				       private_data) != 0) {
+					TALLOC_FREE(mem_ctx);
+					closedir(dir);
+					return count;
+				}
+			}
+
+			rec = db_file_fetch_locked(db, mem_ctx, key);
+			if (rec == NULL) {
+				/* Someone might have deleted it */
+				continue;
+			}
+
+			if (rec->value.dptr == NULL) {
+				TALLOC_FREE(rec);
+				continue;
+			}
+
+			count += 1;
+
+			if (fn(rec, private_data) != 0) {
+				TALLOC_FREE(mem_ctx);
+				closedir(dir);
+				return count;
+			}
+			TALLOC_FREE(rec);
+		}
+
+		closedir(dir);
+	}
+
+	TALLOC_FREE(mem_ctx);
+	return count;
+}
+
+struct db_context *db_open_file(TALLOC_CTX *mem_ctx,
+				struct messaging_context *msg_ctx,
+				const char *name,
+				int hash_size, int tdb_flags,
+				int open_flags, mode_t mode)
+{
+	struct db_context *result = NULL;
+	struct db_file_ctx *ctx;
+
+	if (!(result = TALLOC_ZERO_P(mem_ctx, struct db_context))) {
+		DEBUG(0, ("talloc failed\n"));
+		return NULL;
+	}
+
+	if (!(ctx = TALLOC_P(result, struct db_file_ctx))) {
+		DEBUG(0, ("talloc failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	result->private_data = ctx;
+	result->fetch_locked = db_file_fetch_locked;
+	result->traverse = db_file_traverse;
+
+	ctx->locked_record = NULL;
+	if (!(ctx->dirname = talloc_strdup(ctx, name))) {
+		DEBUG(0, ("talloc failed\n"));
+		TALLOC_FREE(result);
+		return NULL;
+	}
+
+	if (open_flags & O_CREAT) {
+		int ret, i;
+
+		mode |= (mode & S_IRUSR) ? S_IXUSR : 0;
+		mode |= (mode & S_IRGRP) ? S_IXGRP : 0;
+		mode |= (mode & S_IROTH) ? S_IXOTH : 0;
+
+		ret = mkdir(name, mode);
+		if ((ret != 0) && (errno != EEXIST)) {
+			DEBUG(5, ("mkdir(%s,%o) failed: %s\n", name, mode,
+				  strerror(errno)));
+			TALLOC_FREE(result);
+			return NULL;
+		}
+
+		for (i=0; i<256; i++) {
+			char *path;
+			path = talloc_asprintf(result, "%s/%2.2X", name, i);
+			if (path == NULL) {
+				DEBUG(0, ("asprintf failed\n"));
+				TALLOC_FREE(result);
+				return NULL;
+			}
+			ret = mkdir(path, mode);
+			if ((ret != 0) && (errno != EEXIST)) {
+				DEBUG(5, ("mkdir(%s,%o) failed: %s\n", path,
+					  mode, strerror(errno)));
+				TALLOC_FREE(result);
+				return NULL;
+			}
+			TALLOC_FREE(path);
+		}
+	}
+
+	return result;
+}