dovecot-2.1: lib-index: Handle better race condition there dovec...

[dovecot at dovecot.org]

details:   http://hg.dovecot.org/dovecot-2.1/rev/bcef97fb1202
changeset: 14769:bcef97fb1202
user:      Timo Sirainen <tss at iki.fi>
date:      Thu Oct 18 05:55:30 2012 +0300
description:
lib-index: Handle better race condition there dovecot.index.log and .log.2 are the same link.

diffstat:

 src/lib-index/mail-transaction-log-file.c    |  15 ++++++++++-----
 src/lib-index/mail-transaction-log-private.h |   3 +--
 src/lib-index/mail-transaction-log.c         |   6 +++---
 3 files changed, 14 insertions(+), 10 deletions(-)

diffs (83 lines):

diff -r b7c6215b2b7c -r bcef97fb1202 src/lib-index/mail-transaction-log-file.c
--- a/src/lib-index/mail-transaction-log-file.c	Thu Oct 18 05:23:27 2012 +0300
+++ b/src/lib-index/mail-transaction-log-file.c	Thu Oct 18 05:55:30 2012 +0300
@@ -756,6 +756,9 @@
 			   second log file and we're going to overwrite this
 			   first one. */
 		}
+		/* NOTE: here's a race condition where both .log and .log.2
+		   point to the same file. our reading code should ignore that
+		   though by comparing the inodes. */
 	}
 
 	if (file_dotlock_replace(dotlock,
@@ -809,8 +812,7 @@
 	return 0;
 }
 
-int mail_transaction_log_file_open(struct mail_transaction_log_file *file,
-				   bool check_existing)
+int mail_transaction_log_file_open(struct mail_transaction_log_file *file)
 {
 	struct mail_index *index = file->log->index;
         unsigned int i;
@@ -834,10 +836,13 @@
 		ignore_estale = i < MAIL_INDEX_ESTALE_RETRY_COUNT;
 		if (mail_transaction_log_file_stat(file, ignore_estale) < 0)
 			ret = -1;
-		else if (check_existing &&
-			 mail_transaction_log_file_is_dupe(file))
+		else if (mail_transaction_log_file_is_dupe(file)) {
+			/* probably our already opened .log file has been
+			   renamed to .log.2 and we're trying to reopen it.
+			   also possible that hit a race condition where .log
+			   and .log.2 are linked. */
 			return 0;
-		else {
+		} else {
 			ret = mail_transaction_log_file_read_hdr(file,
 								 ignore_estale);
 		}
diff -r b7c6215b2b7c -r bcef97fb1202 src/lib-index/mail-transaction-log-private.h
--- a/src/lib-index/mail-transaction-log-private.h	Thu Oct 18 05:23:27 2012 +0300
+++ b/src/lib-index/mail-transaction-log-private.h	Thu Oct 18 05:55:30 2012 +0300
@@ -117,8 +117,7 @@
 				const char *path);
 void mail_transaction_log_file_free(struct mail_transaction_log_file **file);
 
-int mail_transaction_log_file_open(struct mail_transaction_log_file *file,
-				   bool check_existing);
+int mail_transaction_log_file_open(struct mail_transaction_log_file *file);
 int mail_transaction_log_file_create(struct mail_transaction_log_file *file,
 				     bool reset);
 int mail_transaction_log_file_lock(struct mail_transaction_log_file *file);
diff -r b7c6215b2b7c -r bcef97fb1202 src/lib-index/mail-transaction-log.c
--- a/src/lib-index/mail-transaction-log.c	Thu Oct 18 05:23:27 2012 +0300
+++ b/src/lib-index/mail-transaction-log.c	Thu Oct 18 05:55:30 2012 +0300
@@ -84,7 +84,7 @@
 		return 0;
 
 	file = mail_transaction_log_file_alloc(log, log->filepath);
-	if ((ret = mail_transaction_log_file_open(file, FALSE)) <= 0) {
+	if ((ret = mail_transaction_log_file_open(file)) <= 0) {
 		/* leave the file for _create() */
 		log->open_file = file;
 		return ret;
@@ -322,7 +322,7 @@
 	}
 
 	file = mail_transaction_log_file_alloc(log, log->filepath);
-	if (mail_transaction_log_file_open(file, FALSE) <= 0) {
+	if (mail_transaction_log_file_open(file) <= 0) {
 		mail_transaction_log_file_free(&file);
 		return -1;
 	}
@@ -400,7 +400,7 @@
 
 	/* see if we have it in log.2 file */
 	file = mail_transaction_log_file_alloc(log, log->filepath2);
-	if ((ret = mail_transaction_log_file_open(file, TRUE)) <= 0) {
+	if ((ret = mail_transaction_log_file_open(file)) <= 0) {
 		mail_transaction_log_file_free(&file);
 		return ret;
 	}