1 files changed, 315 insertions, 0 deletions

diff --git a/src/lib-index/mail-index-alloc-cache.c b/src/lib-index/mail-index-alloc-cache.c
new file mode 100644
index 0000000..fe52754
--- /dev/null
+++ b/src/lib-index/mail-index-alloc-cache.c
@@ -0,0 +1,315 @@
+/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "module-context.h"
+#include "eacces-error.h"
+#include "mail-index-private.h"
+#include "mail-index-alloc-cache.h"
+
+#define MAIL_INDEX_ALLOC_CACHE_CONTEXT(obj) \
+	MODULE_CONTEXT(obj, mail_index_alloc_cache_index_module)
+
+/* How many seconds to keep index opened for reuse after it's been closed */
+#define INDEX_CACHE_TIMEOUT 10
+/* How many closed indexes to keep */
+#define INDEX_CACHE_MAX 3
+
+struct mail_index_alloc_cache_list {
+	union mail_index_module_context module_ctx;
+	struct mail_index_alloc_cache_list *next;
+
+	struct mail_index *index;
+	char *mailbox_path;
+	int refcount;
+	bool referenced;
+
+	dev_t index_dir_dev;
+	ino_t index_dir_ino;
+
+	time_t destroy_time;
+};
+
+static MODULE_CONTEXT_DEFINE_INIT(mail_index_alloc_cache_index_module,
+				  &mail_index_module_register);
+static struct mail_index_alloc_cache_list *indexes = NULL;
+static unsigned int indexes_cache_references_count = 0;
+static struct timeout *to_index = NULL;
+
+static struct mail_index_alloc_cache_list *
+mail_index_alloc_cache_add(struct mail_index *index,
+			   const char *mailbox_path, struct stat *st)
+{
+	struct mail_index_alloc_cache_list *list;
+
+	list = i_new(struct mail_index_alloc_cache_list, 1);
+	list->refcount = 1;
+	list->index = index;
+
+	list->mailbox_path = i_strdup(mailbox_path);
+	list->index_dir_dev = st->st_dev;
+	list->index_dir_ino = st->st_ino;
+
+	list->next = indexes;
+	indexes = list;
+
+	MODULE_CONTEXT_SET(index, mail_index_alloc_cache_index_module, list);
+	return list;
+}
+
+static void
+mail_index_alloc_cache_list_unref(struct mail_index_alloc_cache_list *list)
+{
+	i_assert(list->referenced);
+	i_assert(indexes_cache_references_count > 0);
+
+	indexes_cache_references_count--;
+	mail_index_close(list->index);
+	list->referenced = FALSE;
+}
+
+static void
+mail_index_alloc_cache_list_free(struct mail_index_alloc_cache_list *list)
+{
+	i_assert(list->refcount == 0);
+
+	if (list->referenced)
+		mail_index_alloc_cache_list_unref(list);
+	mail_index_free(&list->index);
+	i_free(list->mailbox_path);
+	i_free(list);
+}
+
+static struct mail_index_alloc_cache_list *
+mail_index_alloc_cache_find_and_expire(const char *mailbox_path,
+				       const char *index_dir,
+				       const struct stat *index_st)
+{
+	struct mail_index_alloc_cache_list **indexp, *rec, *match;
+	unsigned int destroy_count;
+	struct stat st;
+
+	destroy_count = 0; match = NULL;
+	for (indexp = &indexes; *indexp != NULL;) {
+		rec = *indexp;
+
+		if (match != NULL) {
+			/* already found the index. we're just going through
+			   the rest of them to drop 0 refcounts */
+		} else if (rec->refcount == 0 && rec->index->open_count == 0) {
+			/* index is already closed. don't even try to
+			   reuse it. */
+		} else if (index_dir != NULL && rec->index_dir_ino != 0) {
+			if (index_st->st_ino == rec->index_dir_ino &&
+			    CMP_DEV_T(index_st->st_dev, rec->index_dir_dev)) {
+				/* make sure the directory still exists.
+				   it might have been renamed and we're trying
+				   to access it via its new path now. */
+				if (stat(rec->index->dir, &st) < 0 ||
+				    st.st_ino != index_st->st_ino ||
+				    !CMP_DEV_T(st.st_dev, index_st->st_dev))
+					rec->destroy_time = 0;
+				else
+					match = rec;
+			}
+		} else if (mailbox_path != NULL && rec->mailbox_path != NULL &&
+			   index_dir == NULL && rec->index_dir_ino == 0) {
+			if (strcmp(mailbox_path, rec->mailbox_path) == 0)
+				match = rec;
+		}
+
+		if (rec->refcount == 0 && rec != match) {
+			if (rec->destroy_time <= ioloop_time ||
+			    destroy_count >= INDEX_CACHE_MAX) {
+				*indexp = rec->next;
+				mail_index_alloc_cache_list_free(rec);
+				continue;
+			} else {
+				destroy_count++;
+			}
+		}
+
+                indexp = &(*indexp)->next;
+	}
+	return match;
+}
+
+struct mail_index *
+mail_index_alloc_cache_get(struct event *parent_event, const char *mailbox_path,
+			   const char *index_dir, const char *prefix)
+{
+	struct mail_index_alloc_cache_list *match;
+	struct stat st;
+
+	/* compare index_dir inodes so we don't break even with symlinks.
+	   if index_dir doesn't exist yet or if using in-memory indexes, just
+	   compare mailbox paths */
+	i_zero(&st);
+	if (index_dir == NULL) {
+		/* in-memory indexes */
+	} else if (stat(index_dir, &st) < 0) {
+		if (errno == ENOENT) {
+			/* it'll be created later */
+		} else if (errno == EACCES) {
+			e_error(parent_event, "%s",
+				eacces_error_get("stat", index_dir));
+		} else {
+			e_error(parent_event, "stat(%s) failed: %m", index_dir);
+		}
+	}
+
+	match = mail_index_alloc_cache_find_and_expire(mailbox_path,
+						       index_dir, &st);
+	if (match == NULL) {
+		struct mail_index *index =
+			mail_index_alloc(parent_event, index_dir, prefix);
+		match = mail_index_alloc_cache_add(index, mailbox_path, &st);
+	} else {
+		match->refcount++;
+	}
+	i_assert(match->index != NULL);
+	return match->index;
+}
+
+struct mail_index *
+mail_index_alloc_cache_find(const char *index_dir)
+{
+	struct mail_index_alloc_cache_list *rec;
+	struct stat st;
+
+	if (stat(index_dir, &st) < 0) {
+		if (errno != ENOENT)
+			i_error("stat(%s) failed: %m", index_dir);
+		return NULL;
+	}
+
+	for (rec = indexes; rec != NULL; rec = rec->next) {
+		if (st.st_ino == rec->index_dir_ino &&
+		    CMP_DEV_T(st.st_dev, rec->index_dir_dev))
+			return rec->index;
+	}
+	return NULL;
+}
+
+static bool destroy_unrefed(unsigned int min_destroy_count)
+{
+	struct mail_index_alloc_cache_list **list, *rec;
+	bool destroyed = FALSE;
+	bool seen_ref0 = FALSE;
+
+	for (list = &indexes; *list != NULL;) {
+		rec = *list;
+
+		if (rec->refcount == 0 &&
+		    (min_destroy_count > 0 || rec->destroy_time <= ioloop_time)) {
+			*list = rec->next;
+			destroyed = TRUE;
+			mail_index_alloc_cache_list_free(rec);
+			if (min_destroy_count > 0)
+				min_destroy_count--;
+		} else {
+			if (rec->refcount == 0)
+				seen_ref0 = TRUE;
+			if (min_destroy_count > 0 &&
+			    rec->index->open_count == 1 &&
+			    rec->referenced) {
+				/* we're the only one keeping this index open.
+				   we might be here, because the caller is
+				   deleting this mailbox and wants its indexes
+				   to be closed. so close it. */
+				destroyed = TRUE;
+				mail_index_alloc_cache_list_unref(rec);
+			}
+			list = &(*list)->next;
+		}
+	}
+
+	if (!seen_ref0 && to_index != NULL)
+		timeout_remove(&to_index);
+	return destroyed;
+}
+
+static void ATTR_NULL(1)
+index_removal_timeout(void *context ATTR_UNUSED)
+{
+	destroy_unrefed(0);
+}
+
+void mail_index_alloc_cache_unref(struct mail_index **_index)
+{
+	struct mail_index *index = *_index;
+	struct mail_index_alloc_cache_list *list, **listp;
+
+	*_index = NULL;
+	list = NULL;
+	for (listp = &indexes; *listp != NULL; listp = &(*listp)->next) {
+		if ((*listp)->index == index) {
+			list = *listp;
+			break;
+		}
+	}
+
+	i_assert(list != NULL);
+	i_assert(list->refcount > 0);
+
+	list->refcount--;
+	list->destroy_time = ioloop_time + INDEX_CACHE_TIMEOUT;
+
+	if (list->refcount == 0 && index->open_count == 0) {
+		/* index was already closed. don't even try to cache it. */
+		*listp = list->next;
+		mail_index_alloc_cache_list_free(list);
+	} else if (to_index == NULL) {
+		/* Add to root ioloop in case we got here from an inner
+		   ioloop which gets destroyed too early. */
+		to_index = timeout_add_to(io_loop_get_root(),
+					  INDEX_CACHE_TIMEOUT*1000/2,
+					  index_removal_timeout, NULL);
+	}
+}
+
+void mail_index_alloc_cache_destroy_unrefed(void)
+{
+	destroy_unrefed(UINT_MAX);
+}
+
+void mail_index_alloc_cache_index_opened(struct mail_index *index)
+{
+	struct mail_index_alloc_cache_list *list =
+		MAIL_INDEX_ALLOC_CACHE_CONTEXT(index);
+	struct stat st;
+
+	if (list != NULL && list->index_dir_ino == 0 &&
+	    !MAIL_INDEX_IS_IN_MEMORY(index)) {
+		/* newly created index directory. update its stat. */
+		if (stat(index->dir, &st) == 0) {
+			list->index_dir_ino = st.st_ino;
+			list->index_dir_dev = st.st_dev;
+		}
+	}
+}
+
+void mail_index_alloc_cache_index_closing(struct mail_index *index)
+{
+	struct mail_index_alloc_cache_list *list =
+		MAIL_INDEX_ALLOC_CACHE_CONTEXT(index);
+
+	i_assert(index->open_count > 0);
+	if (index->open_count > 1 || list == NULL)
+		return;
+
+	if (list->referenced) {
+		/* we're closing our referenced index */
+		return;
+	}
+	while (indexes_cache_references_count > INDEX_CACHE_MAX) {
+		if (!destroy_unrefed(1)) {
+			/* our cache is full already, don't keep more */
+			return;
+		}
+	}
+	/* keep the index referenced for caching */
+	indexes_cache_references_count++;
+	list->referenced = TRUE;
+	index->open_count++;
+}