added a syncops VFS module for filesystems which do not guarantee meta-data operations are immediately committed to disk in stable form. Essential for clustered Samba setups

(This used to be commit 8b19cb17b9ae9e1cd4a96df6e7dedb75aff7ee96)

1 files changed, 210 insertions, 0 deletions

diff --git a/source3/modules/vfs_syncops.c b/source3/modules/vfs_syncops.c
new file mode 100644
index 0000000000..3aa89b40a6
--- /dev/null
+++ b/source3/modules/vfs_syncops.c
@@ -0,0 +1,210 @@
+/* 
+ * ensure meta data operations are performed synchronously
+ *
+ * Copyright (C) Andrew Tridgell     2007
+ *
+ * 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.
+ */
+
+#include "includes.h"
+
+/*
+
+  Some filesystems (even some journaled filesystems) require that a
+  fsync() be performed on many meta data operations to ensure that the
+  operation is guaranteed to remain in the filesystem after a power
+  failure. This is particularly important for some cluster filesystems
+  which are participating in a node failover system with clustered
+  Samba
+
+  On those filesystems this module provides a way to perform those
+  operations safely.  
+ */
+
+/*
+  most of the performance loss with this module is in fsync on close(). 
+  You can disable that with syncops:onclose = no
+ */
+static bool sync_onclose;
+
+/*
+  given a filename, find the parent directory
+ */
+static char *parent_dir(TALLOC_CTX *mem_ctx, const char *name)
+{
+	const char *p = strrchr(name, '/');
+	if (p == NULL) {
+		return talloc_strdup(mem_ctx, ".");
+	}
+	return talloc_strndup(mem_ctx, name, (p+1) - name);
+}
+
+/*
+  fsync a directory by name
+ */
+static void syncops_sync_directory(const char *dname)
+{
+#ifdef O_DIRECTORY
+	int fd = open(dname, O_DIRECTORY|O_RDONLY);
+	if (fd != -1) {
+		fsync(fd);
+		close(fd);
+	}
+#else
+	DIR *d = opendir(dname);
+	if (d != NULL) {
+		fsync(dirfd(d));
+		closedir(d);
+	}
+#endif
+}
+
+/*
+  sync two meta data changes for 2 names
+ */
+static void syncops_two_names(const char *name1, const char *name2)
+{
+	TALLOC_CTX *tmp_ctx = talloc_new(NULL);
+	char *parent1, *parent2;
+	parent1 = parent_dir(tmp_ctx, name1);
+	parent2 = parent_dir(tmp_ctx, name2);
+	if (!parent1 || !parent2) {
+		talloc_free(tmp_ctx);
+		return;
+	}
+	syncops_sync_directory(parent1);
+	if (strcmp(parent1, parent2) != 0) {
+		syncops_sync_directory(parent2);		
+	}
+	talloc_free(tmp_ctx);
+}
+
+/*
+  sync two meta data changes for 1 names
+ */
+static void syncops_name(const char *name)
+{
+	char *parent;
+	parent = parent_dir(NULL, name);
+	if (parent) {
+		syncops_sync_directory(parent);
+		talloc_free(parent);
+	}
+}
+
+
+/*
+  rename needs special handling, as we may need to fsync two directories
+ */
+static int syncops_rename(vfs_handle_struct *handle,
+			  const char *oldname, const char *newname)
+{
+	int ret = SMB_VFS_NEXT_RENAME(handle, oldname, newname);
+	if (ret == 0) {
+		syncops_two_names(oldname, newname);
+	}
+	return ret;
+}
+
+/* handle the rest with a macro */
+#define SYNCOPS_NEXT(op, fname, args) do {   \
+	int ret = SMB_VFS_NEXT_ ## op args; \
+	if (ret == 0 && fname) syncops_name(fname); \
+	return ret; \
+} while (0)
+
+static int syncops_symlink(vfs_handle_struct *handle,
+			   const char *oldname, const char *newname)
+{
+	SYNCOPS_NEXT(SYMLINK, newname, (handle, oldname, newname));
+}
+
+static int syncops_link(vfs_handle_struct *handle,
+			 const char *oldname, const char *newname)
+{
+	SYNCOPS_NEXT(LINK, newname, (handle, oldname, newname));
+}
+
+static int syncops_open(vfs_handle_struct *handle,
+			const char *fname, files_struct *fsp, int flags, mode_t mode)
+{
+	SYNCOPS_NEXT(OPEN, (flags&O_CREAT?fname:NULL), (handle, fname, fsp, flags, mode));
+}
+
+static int syncops_unlink(vfs_handle_struct *handle, const char *fname)
+{
+        SYNCOPS_NEXT(UNLINK, fname, (handle, fname));
+}
+
+static int syncops_mknod(vfs_handle_struct *handle,
+			 const char *fname, mode_t mode, SMB_DEV_T dev)
+{
+        SYNCOPS_NEXT(MKNOD, fname, (handle, fname, mode, dev));
+}
+
+static int syncops_mkdir(vfs_handle_struct *handle,  const char *fname, mode_t mode)
+{
+        SYNCOPS_NEXT(MKDIR, fname, (handle, fname, mode));
+}
+
+static int syncops_rmdir(vfs_handle_struct *handle,  const char *fname)
+{
+        SYNCOPS_NEXT(RMDIR, fname, (handle, fname));
+}
+
+/* close needs to be handled specially */
+static int syncops_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
+{
+	if (fsp->can_write && sync_onclose) {
+		/* ideally we'd only do this if we have written some
+		 data, but there is no flag for that in fsp yet. */
+		fsync(fd);
+	}
+	return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
+}
+
+
+/* VFS operations structure */
+
+static vfs_op_tuple syncops_ops[] = {
+	/* directory operations */
+        {SMB_VFS_OP(syncops_mkdir),       SMB_VFS_OP_MKDIR,       SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_rmdir),       SMB_VFS_OP_RMDIR,       SMB_VFS_LAYER_TRANSPARENT},
+
+        /* File operations */
+        {SMB_VFS_OP(syncops_open),       SMB_VFS_OP_OPEN,     SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_rename),     SMB_VFS_OP_RENAME,   SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_unlink),     SMB_VFS_OP_UNLINK,   SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_symlink),    SMB_VFS_OP_SYMLINK,  SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_link),       SMB_VFS_OP_LINK,     SMB_VFS_LAYER_TRANSPARENT},
+        {SMB_VFS_OP(syncops_mknod),      SMB_VFS_OP_MKNOD,    SMB_VFS_LAYER_TRANSPARENT},
+	{SMB_VFS_OP(syncops_close), 	 SMB_VFS_OP_CLOSE,    SMB_VFS_LAYER_TRANSPARENT},
+
+	{SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
+};
+
+NTSTATUS vfs_syncops_init(void)
+{
+	NTSTATUS ret;
+
+	ret = smb_register_vfs(SMB_VFS_INTERFACE_VERSION, "syncops", syncops_ops);
+
+	if (!NT_STATUS_IS_OK(ret))
+		return ret;
+
+	sync_onclose = lp_parm_bool(-1, "syncops", "onclose", true);
+	
+	return ret;
+}