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Commit79ce29c

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Retry short writes when flushing WAL.
We don't normally bother retrying when the number of bytes written bywrite() is short of what was requested. It is generally assumed that awrite() 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 mostwrite()s in the backend (up to wal_buffers), so there's more room forsurprises.Also retry on EINTR. All signals used in the backend are flagged SA_RESTARTnowadays, so it shouldn't happen, but better to be defensive.
1 parent129759d commit79ce29c

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1 file changed

+20
-12
lines changed
  • src/backend/access/transam

1 file changed

+20
-12
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 20 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1606,6 +1606,8 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
16061606
{
16071607
char*from;
16081608
Sizenbytes;
1609+
Sizenleft;
1610+
intwritten;
16091611

16101612
/* Need to seek in the file? */
16111613
if (openLogOff!=startoffset)
@@ -1622,19 +1624,25 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
16221624
/* OK to write the page(s) */
16231625
from=XLogCtl->pages+startidx* (Size)XLOG_BLCKSZ;
16241626
nbytes=npages* (Size)XLOG_BLCKSZ;
1625-
errno=0;
1626-
if (write(openLogFile,from,nbytes)!=nbytes)
1627+
nleft=nbytes;
1628+
do
16271629
{
1628-
/* if write didn't set errno, assume no disk space */
1629-
if (errno==0)
1630-
errno=ENOSPC;
1631-
ereport(PANIC,
1632-
(errcode_for_file_access(),
1633-
errmsg("could not write to log file %s "
1634-
"at offset %u, length %lu: %m",
1635-
XLogFileNameP(ThisTimeLineID,openLogSegNo),
1636-
openLogOff, (unsigned long)nbytes)));
1637-
}
1630+
errno=0;
1631+
written=write(openLogFile,from,nleft);
1632+
if (written <=0)
1633+
{
1634+
if (errno==EINTR)
1635+
continue;
1636+
ereport(PANIC,
1637+
(errcode_for_file_access(),
1638+
errmsg("could not write to log file %s "
1639+
"at offset %u, length %lu: %m",
1640+
XLogFileNameP(ThisTimeLineID,openLogSegNo),
1641+
openLogOff, (unsigned long)nbytes)));
1642+
}
1643+
nleft-=written;
1644+
from+=written;
1645+
}while (nleft>0);
16381646

16391647
/* Update state for write */
16401648
openLogOff+=nbytes;

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