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authorRusty Russell <rusty@rustcorp.com.au>2012-06-22 09:44:41 +0930
committerRusty Russell <rusty@rustcorp.com.au>2012-06-22 07:35:17 +0200
commit8113d53bb421217040a8184ba00f61308e8959d6 (patch)
treecddf15c4f912758d244232ae01a91121d064b42f
parent735290f474a34986be4c66eb0bdf0b0ba14da970 (diff)
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util: ntdb_new() supports NTDB_CLEAR_IF_FIRST.
There are various issues with NTDB_CLEAR_IF_FIRST which makes it better if we don't have to use it, but much of the code does, so we fake up support here. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--lib/util/util_ntdb.c85
-rw-r--r--lib/util/util_ntdb.h15
2 files changed, 99 insertions, 1 deletions
diff --git a/lib/util/util_ntdb.c b/lib/util/util_ntdb.c
index 9c3e2a5254..10d60c2b84 100644
--- a/lib/util/util_ntdb.c
+++ b/lib/util/util_ntdb.c
@@ -21,6 +21,81 @@
#include "includes.h"
#include "util_ntdb.h"
#include "lib/param/param.h"
+#include "replace.h"
+#include "system/filesys.h"
+
+/*
+ * This handles NTDB_CLEAR_IF_FIRST.
+ *
+ * It's a bad idea for new code, but S3 uses it quite a bit.
+ */
+static enum NTDB_ERROR clear_if_first(int fd, void *unused)
+{
+ /* We hold a lock offset 4 always, so we can tell if anyone else is. */
+ struct flock fl;
+
+ fl.l_type = F_WRLCK;
+ fl.l_whence = SEEK_SET;
+ fl.l_start = 4; /* ACTIVE_LOCK */
+ fl.l_len = 1;
+
+ if (fcntl(fd, F_SETLK, &fl) == 0) {
+ /* We must be first ones to open it w/ NTDB_CLEAR_IF_FIRST! */
+ if (ftruncate(fd, 0) != 0) {
+ return NTDB_ERR_IO;
+ }
+ }
+ fl.l_type = F_RDLCK;
+ if (fcntl(fd, F_SETLKW, &fl) != 0) {
+ return NTDB_ERR_IO;
+ }
+ return NTDB_SUCCESS;
+}
+
+/* We only need these for the CLEAR_IF_FIRST lock. */
+static int reacquire_cif_lock(struct ntdb_context *ntdb, bool *fail)
+{
+ struct flock fl;
+ union ntdb_attribute cif;
+
+ cif.openhook.base.attr = NTDB_ATTRIBUTE_OPENHOOK;
+ cif.openhook.base.next = NULL;
+
+ if (ntdb_get_attribute(ntdb, &cif) != NTDB_SUCCESS
+ || cif.openhook.fn != clear_if_first) {
+ return 0;
+ }
+
+ /* We hold a lock offset 4 always, so we can tell if anyone else is. */
+ fl.l_type = F_RDLCK;
+ fl.l_whence = SEEK_SET;
+ fl.l_start = 4; /* ACTIVE_LOCK */
+ fl.l_len = 1;
+ if (fcntl(ntdb_fd(ntdb), F_SETLKW, &fl) != 0) {
+ *fail = true;
+ return -1;
+ }
+ return 0;
+}
+
+/* You only need this on databases with NTDB_CLEAR_IF_FIRST */
+int ntdb_reopen(struct ntdb_context *ntdb)
+{
+ bool unused;
+ return reacquire_cif_lock(ntdb, &unused);
+}
+
+/* You only need to do this if you have NTDB_CLEAR_IF_FIRST databases, and
+ * the parent will go away before this child. */
+int ntdb_reopen_all(void)
+{
+ bool fail = false;
+
+ ntdb_foreach(reacquire_cif_lock, &fail);
+ if (fail)
+ return -1;
+ return 0;
+}
static void *ntdb_talloc(const void *owner, size_t len, void *priv_data)
{
@@ -74,7 +149,7 @@ struct ntdb_context *ntdb_new(TALLOC_CTX *ctx,
union ntdb_attribute *attr,
struct loadparm_context *lp_ctx)
{
- union ntdb_attribute log_attr, alloc_attr;
+ union ntdb_attribute log_attr, alloc_attr, open_attr;
struct ntdb_context *ntdb;
if (lp_ctx && !lpcfg_use_mmap(lp_ctx)) {
@@ -96,6 +171,14 @@ struct ntdb_context *ntdb_new(TALLOC_CTX *ctx,
alloc_attr.alloc.expand = ntdb_expand;
alloc_attr.alloc.free = ntdb_free;
+ if (ntdb_flags & NTDB_CLEAR_IF_FIRST) {
+ log_attr.base.next = &open_attr;
+ open_attr.openhook.base.attr = NTDB_ATTRIBUTE_OPENHOOK;
+ open_attr.openhook.base.next = attr;
+ open_attr.openhook.fn = clear_if_first;
+ ntdb_flags &= ~NTDB_CLEAR_IF_FIRST;
+ }
+
ntdb = ntdb_open(name, ntdb_flags, open_flags, mode, &alloc_attr);
if (!ntdb) {
return NULL;
diff --git a/lib/util/util_ntdb.h b/lib/util/util_ntdb.h
index a5eab7f436..d65d8b6f7b 100644
--- a/lib/util/util_ntdb.h
+++ b/lib/util/util_ntdb.h
@@ -27,6 +27,21 @@
struct loadparm_context;
union ntdb_attribute;
+
+/* You only need this on databases with NTDB_CLEAR_IF_FIRST */
+int ntdb_reopen(struct ntdb_context *ntdb);
+
+/* You only need to do this if you have NTDB_CLEAR_IF_FIRST databases, and
+ * the parent will go away before this child. */
+int ntdb_reopen_all(void);
+
+/*
+ * This is like TDB_CLEAR_IF_FIRST, for use with ntdb_new.
+ *
+ * It's a bad idea for new code.
+ */
+#define NTDB_CLEAR_IF_FIRST 1048576
+
/***************************************************************
Open an NTDB using talloc: it will be allocated off the context, and
all NTDB_DATA.dptr are allocated as children of the ntdb context.