Rework error messages around file handling

Some error messages related to file handling are using the code path
context to define their state.  For example, 2PC-related errors are
referring to "two-phase status files", or "relation mapping file" is
used for catalog-to-filenode mapping, however those prove to be
difficult to translate, and are not more helpful than just referring to
the path of the file being worked on.  So simplify all those error
messages by just referring to files with their path used.  In some
cases, like the manipulation of WAL segments, the context is actually
helpful so those are kept.

Calls to the system function read() have also been rather inconsistent
with their error handling sometimes not reporting the number of bytes
read, and some other code paths trying to use an errno which has not
been set.  The in-core functions are using a more consistent pattern
with this patch, which checks for both errno if set or if an
inconsistent read is happening.

So as to care about pluralization when reading an unexpected number of
byte(s), "could not read: read %d of %zu" is used as error message, with
%d field being the output result of read() and %zu the expected size.
This simplifies the work of translators with less variations of the same
message.

Author: Michael Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20180520000522.GB1603@paquier.xyz

1 files changed, 27 insertions, 13 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 4049deb968e..bebe6405de5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -3408,21 +3408,24 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno,
 
 		if (nread > 0)
 		{
+			int			r;
+
 			if (nread > sizeof(buffer))
 				nread = sizeof(buffer);
 			errno = 0;
 			pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_READ);
-			if (read(srcfd, buffer, nread) != nread)
+			r = read(srcfd, buffer, nread);
+			if (r != nread)
 			{
-				if (errno != 0)
+				if (r < 0)
 					ereport(ERROR,
 							(errcode_for_file_access(),
 							 errmsg("could not read file \"%s\": %m",
 									path)));
 				else
 					ereport(ERROR,
-							(errmsg("not enough data in file \"%s\"",
-									path)));
+							(errmsg("could not read file \"%s\": read %d of %zu",
+									path, r, (Size) nread)));
 			}
 			pgstat_report_wait_end();
 		}
@@ -4544,7 +4547,7 @@ ReadControlFile(void)
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
-				 errmsg("could not open control file \"%s\": %m",
+				 errmsg("could not open file \"%s\": %m",
 						XLOG_CONTROL_FILE)));
 
 	pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_READ);
@@ -4554,10 +4557,12 @@ ReadControlFile(void)
 		if (r < 0)
 			ereport(PANIC,
 					(errcode_for_file_access(),
-					 errmsg("could not read from control file: %m")));
+					 errmsg("could not read file \"%s\": %m",
+							XLOG_CONTROL_FILE)));
 		else
 			ereport(PANIC,
-					(errmsg("could not read from control file: read %d bytes, expected %d", r, (int) sizeof(ControlFileData))));
+					(errmsg("could not read file \"%s\": read %d of %zu",
+							XLOG_CONTROL_FILE, r, sizeof(ControlFileData))));
 	}
 	pgstat_report_wait_end();
 
@@ -11689,6 +11694,7 @@ XLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen,
 	int			emode = private->emode;
 	uint32		targetPageOff;
 	XLogSegNo	targetSegNo PG_USED_FOR_ASSERTS_ONLY;
+	int			r;
 
 	XLByteToSeg(targetPagePtr, targetSegNo, wal_segment_size);
 	targetPageOff = XLogSegmentOffset(targetPagePtr, wal_segment_size);
@@ -11782,18 +11788,26 @@ retry:
 	}
 
 	pgstat_report_wait_start(WAIT_EVENT_WAL_READ);
-	if (read(readFile, readBuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+	r = read(readFile, readBuf, XLOG_BLCKSZ);
+	if (r != XLOG_BLCKSZ)
 	{
 		char		fname[MAXFNAMELEN];
 		int			save_errno = errno;
 
 		pgstat_report_wait_end();
 		XLogFileName(fname, curFileTLI, readSegNo, wal_segment_size);
-		errno = save_errno;
-		ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen),
-				(errcode_for_file_access(),
-				 errmsg("could not read from log segment %s, offset %u: %m",
-						fname, readOff)));
+		if (r < 0)
+		{
+			errno = save_errno;
+			ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen),
+					(errcode_for_file_access(),
+					 errmsg("could not read from log segment %s, offset %u: %m",
+							fname, readOff)));
+		}
+		else
+			ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen),
+					(errmsg("could not read from log segment %s, offset %u: read %d of %zu",
+							fname, readOff, r, (Size) XLOG_BLCKSZ)));
 		goto next_record_is_invalid;
 	}
 	pgstat_report_wait_end();