Make xenstored use tdb, transactions can soft-fail (EAGAIN)

Transactions no longer take root dir, no longer lock & block: commit can fail spuriously with EAGAIN, not ETIMEDOUT.
Speeds up transactions by over 1000 times, should be NFS safe.
New program: xs_tdb_dump to dump raw TDB contents.
Don't do failure testing: we are no longer robust against all ENOMEM 8(
Introduce "struct node" which contains perms, children and data.
Make struct xs_permissions unpadded, so we can write to tdb w/o valgrind complaints.
Gently modify TDB to use talloc, not do alloc on tdb_delete.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 81 insertions, 0 deletions

diff --git a/tools/xenstore/xs_tdb_dump.c b/tools/xenstore/xs_tdb_dump.c
new file mode 100644
index 0000000000..1cab37ed6d
--- /dev/null
+++ b/tools/xenstore/xs_tdb_dump.c
@@ -0,0 +1,81 @@
+/* Simple program to dump out all records of TDB */
+#include <stdint.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+#include "xs_lib.h"
+#include "tdb.h"
+#include "talloc.h"
+#include "utils.h"
+
+struct record_hdr {
+	u32 num_perms;
+	u32 datalen;
+	u32 childlen;
+	struct xs_permissions perms[0];
+};
+
+static u32 total_size(struct record_hdr *hdr)
+{
+	return sizeof(*hdr) + hdr->num_perms * sizeof(struct xs_permissions) 
+		+ hdr->datalen + hdr->childlen;
+}
+
+static char perm_to_char(enum xs_perm_type perm)
+{
+	return perm == XS_PERM_READ ? 'r' :
+		perm == XS_PERM_WRITE ? 'w' :
+		perm == XS_PERM_NONE ? '-' :
+		perm == (XS_PERM_READ|XS_PERM_WRITE) ? 'b' :
+		'?';
+}
+
+int main(int argc, char *argv[])
+{
+	TDB_DATA key;
+	TDB_CONTEXT *tdb;
+
+	if (argc != 2)
+		barf("Usage: xs_tdb_dump <tdbfile>");
+
+	tdb = tdb_open(talloc_strdup(NULL, argv[1]), 0, 0, O_RDONLY, 0);
+	if (!tdb)
+		barf_perror("Could not open %s", argv[1]);
+
+	key = tdb_firstkey(tdb);
+	while (key.dptr) {
+		TDB_DATA data;
+		struct record_hdr *hdr;
+
+		data = tdb_fetch(tdb, key);
+		hdr = (void *)data.dptr;
+		if (data.dsize < sizeof(*hdr))
+			fprintf(stderr, "%.*s: BAD truncated\n",
+				key.dsize, key.dptr);
+		else if (data.dsize != total_size(hdr))
+			fprintf(stderr, "%.*s: BAD length %i for %i/%i/%i (%i)\n",
+				key.dsize, key.dptr, data.dsize,
+				hdr->num_perms, hdr->datalen,
+				hdr->childlen, total_size(hdr));
+		else {
+			unsigned int i;
+			char *p;
+
+			printf("%.*s: ", key.dsize, key.dptr);
+			for (i = 0; i < hdr->num_perms; i++)
+				printf("%s%c%i",
+				       i == 0 ? "" : ",",
+				       perm_to_char(hdr->perms[i].perms),
+				       hdr->perms[i].id);
+			p = (void *)&hdr->perms[hdr->num_perms];
+			printf(" %.*s\n", hdr->datalen, p);
+			p += hdr->datalen;
+			for (i = 0; i < hdr->childlen; i += strlen(p+i)+1)
+				printf("\t-> %s\n", p+i);
+		}
+		key = tdb_nextkey(tdb, key);
+	}
+	return 0;
+}
+