From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Tue, 1 Oct 2019 20:33:47 +0000 (+0300)
Subject: lib-index: Don't rewrite dovecot.index if another process has already done it
X-Git-Tag: 2.3.11.2~516
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e8754c0e182e3f8dab4c0b1a01032d0e5c82c71f;p=thirdparty%2Fdovecot%2Fcore.git

lib-index: Don't rewrite dovecot.index if another process has already done it

This mainly happened when there were multiple sessions accessing the index
at the same time.
---

diff --git a/src/lib-index/mail-index-map-read.c b/src/lib-index/mail-index-map-read.c
index bf219320f4..73f0efc11c 100644
--- a/src/lib-index/mail-index-map-read.c
+++ b/src/lib-index/mail-index-map-read.c
@@ -313,6 +313,7 @@ mail_index_map_latest_file(struct mail_index *index, const char **reason_r)
 
 	*reason_r = NULL;
 
+	index->reopen_main_index = FALSE;
 	ret = mail_index_reopen_if_changed(index, reason_r);
 	if (ret <= 0) {
 		if (ret < 0)
@@ -418,7 +419,7 @@ int mail_index_map(struct mail_index *index,
 		index->map = mail_index_map_alloc(index);
 
 	/* first try updating the existing mapping from transaction log. */
-	if (index->initial_mapped) {
+	if (index->initial_mapped && !index->reopen_main_index) {
 		/* we're not creating/opening the index.
 		   sync this as a view from transaction log. */
 		ret = mail_index_sync_map(&index->map, type, FALSE, "initial mapping");
diff --git a/src/lib-index/mail-index-private.h b/src/lib-index/mail-index-private.h
index 67e63d2a7f..5faf525f8d 100644
--- a/src/lib-index/mail-index-private.h
+++ b/src/lib-index/mail-index-private.h
@@ -223,6 +223,7 @@ struct mail_index {
 	bool modseqs_enabled:1;
 	bool initial_create:1;
 	bool initial_mapped:1;
+	bool reopen_main_index:1;
 	bool fscked:1;
 };
 
diff --git a/src/lib-index/mail-index-write.c b/src/lib-index/mail-index-write.c
index 791cf9f1ce..c0fd2f84cb 100644
--- a/src/lib-index/mail-index-write.c
+++ b/src/lib-index/mail-index-write.c
@@ -1,6 +1,7 @@
 /* Copyright (c) 2003-2018 Dovecot authors, see the included COPYING file */
 
 #include "lib.h"
+#include "nfs-workarounds.h"
 #include "read-full.h"
 #include "write-full.h"
 #include "ostream.h"
@@ -116,6 +117,40 @@ static int mail_index_recreate(struct mail_index *index)
 	return ret;
 }
 
+static bool mail_index_should_recreate(struct mail_index *index)
+{
+	struct stat st1, st2;
+
+	if (nfs_safe_stat(index->filepath, &st1) < 0) {
+		if (errno != ENOENT) {
+			mail_index_set_syscall_error(index, "stat()");
+			return FALSE;
+		} else if (index->fd == -1) {
+			/* main index hasn't been created yet */
+			return TRUE;
+		} else {
+			/* mailbox was just deleted? don't log an error */
+			return FALSE;
+		}
+	}
+	if (index->fd == -1) {
+		/* main index was just created by another process */
+		return FALSE;
+	}
+	if (fstat(index->fd, &st2) < 0) {
+		if (!ESTALE_FSTAT(errno))
+			mail_index_set_syscall_error(index, "fstat()");
+		return FALSE;
+	}
+	if (st1.st_ino != st2.st_ino ||
+	    !CMP_DEV_T(st1.st_dev, st2.st_dev)) {
+		/* Index has already been recreated since we last read it.
+		   We can't trust our decisions about whether to recreate it. */
+		return FALSE;
+	}
+	return TRUE;
+}
+
 void mail_index_write(struct mail_index *index, bool want_rotate,
 		      const char *reason)
 {
@@ -152,7 +187,12 @@ void mail_index_write(struct mail_index *index, bool want_rotate,
 		}
 	}
 
-	if (!MAIL_INDEX_IS_IN_MEMORY(index)) {
+	if (MAIL_INDEX_IS_IN_MEMORY(index))
+		;
+	else if (!mail_index_should_recreate(index)) {
+		/* make sure we don't keep getting back in here */
+		index->reopen_main_index = TRUE;
+	} else {
 		e_debug(index->event, "Recreating %s because: %s",
 			index->filepath, reason);
 		if (mail_index_recreate(index) < 0) {