From 79ce29c734c6a652b2f7193bda537cff0c8eb8c1 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Mon, 1 Jul 2013 09:36:00 +0300 Subject: [PATCH] Retry short writes when flushing WAL. We don't normally bother retrying when the number of bytes written by write() is short of what was requested. It is generally assumed that a write() to disk doesn't return short, unless you run out of disk space. While writing the WAL, however, it seems prudent to try a bit harder, because a failure leads to PANIC. The write() is also much larger than most write()s in the backend (up to wal_buffers), so there's more room for surprises. Also retry on EINTR. All signals used in the backend are flagged SA_RESTART nowadays, so it shouldn't happen, but better to be defensive. --- src/backend/access/transam/xlog.c | 32 +++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 6644703369..0ce661bf9f 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1606,6 +1606,8 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch) { char *from; Size nbytes; + Size nleft; + int written; /* Need to seek in the file? */ if (openLogOff != startoffset) @@ -1622,19 +1624,25 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch) /* OK to write the page(s) */ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ; nbytes = npages * (Size) XLOG_BLCKSZ; - errno = 0; - if (write(openLogFile, from, nbytes) != nbytes) + nleft = nbytes; + do { - /* if write didn't set errno, assume no disk space */ - if (errno == 0) - errno = ENOSPC; - ereport(PANIC, - (errcode_for_file_access(), - errmsg("could not write to log file %s " - "at offset %u, length %lu: %m", - XLogFileNameP(ThisTimeLineID, openLogSegNo), - openLogOff, (unsigned long) nbytes))); - } + errno = 0; + written = write(openLogFile, from, nleft); + if (written <= 0) + { + if (errno == EINTR) + continue; + ereport(PANIC, + (errcode_for_file_access(), + errmsg("could not write to log file %s " + "at offset %u, length %lu: %m", + XLogFileNameP(ThisTimeLineID, openLogSegNo), + openLogOff, (unsigned long) nbytes))); + } + nleft -= written; + from += written; + } while (nleft > 0); /* Update state for write */ openLogOff += nbytes; -- 2.40.0