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Address set of issues with errno handling

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System calls mixed up in error code paths are causing two issues which
several code paths have not correctly handled:
1) For write() calls, sometimes the system may return less bytes than
what has been written without errno being set.  Some paths were careful
enough to consider that case, and assumed that errno should be set to
ENOSPC, other calls missed that.
2) errno generated by a system call is overwritten by other system calls
which may succeed once an error code path is taken, causing what is
reported to the user to be incorrect.

This patch uses the brute-force approach of correcting all those code
paths.  Some refactoring could happen in the future, but this is let as
future work, which is not targeted for back-branches anyway.

Author: Michael Paquier
Reviewed-by: Ashutosh Sharma
Discussion: https://postgr.es/m/20180622061535.GD5215@paquier.xyz
This commit is contained in:
Michael Paquier
2018-06-25 11:19:05 +09:00
parent 370e68ae1c
commit 6cb3372411
10 changed files with 118 additions and 6 deletions
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6
src/backend/access/transam/xlogutils.c
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@ -718,9 +718,10 @@ XLogRead(char *buf, int segsize, TimeLineID tli, XLogRecPtr startptr,
if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
{
char path[MAXPGPATH];
int save_errno = errno;
XLogFilePath(path, tli, sendSegNo, segsize);
errno = save_errno;
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not seek in log segment %s to offset %u: %m",
@ -741,9 +742,10 @@ XLogRead(char *buf, int segsize, TimeLineID tli, XLogRecPtr startptr,
if (readbytes <= 0)
{
char path[MAXPGPATH];
int save_errno = errno;
XLogFilePath(path, tli, sendSegNo, segsize);
errno = save_errno;
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from log segment %s, offset %u, length %lu: %m",