Improve error handling in RemovePgTempFiles().

Modify this function and its subsidiaries so that syscall failures are
reported via ereport(LOG), rather than silently ignored as before.
We don't want to throw a hard ERROR, as that would prevent database
startup, and getting rid of leftover temporary files is not important
enough for that.  On the other hand, not reporting trouble at all
seems like an odd choice not in line with current project norms,
especially since any failure here is quite unexpected.

On the same reasoning, adjust these functions' AllocateDir/ReadDir calls
so that failure to scan a directory results in LOG not ERROR.  I also
removed the previous practice of silently ignoring ENOENT failures during
directory opens --- there are some corner cases where that could happen
given a previous database crash, but that seems like a bad excuse for
ignoring a condition that isn't expected in most cases.  A LOG message
during postmaster start seems OK in such situations, and better than
no output at all.

In passing, make RemovePgTempRelationFiles' test for "is the file name
all digits" look more like the way it's done elsewhere.

Discussion: https://postgr.es/m/19907.1512402254@sss.pgh.pa.us

Author: tglsfdc

src/backend/storage/file/fd.c

@@ -2994,6 +2994,10 @@ CleanupTempFiles(bool isProcExit)
  * the temp files for debugging purposes.  This does however mean that
  * OpenTemporaryFile had better allow for collision with an existing temp
  * file name.
+ *
+ * NOTE: this function and its subroutines generally report syscall failures
+ * with ereport(LOG) and keep going.  Removing temp files is not so critical
+ * that we should fail to start the database when we can't do it.
  */
 void
 RemovePgTempFiles(void)
@@ -3014,7 +3018,7 @@ RemovePgTempFiles(void)
 	 */
 	spc_dir = AllocateDir("pg_tblspc");
 
-	while ((spc_de = ReadDir(spc_dir, "pg_tblspc")) != NULL)
+	while ((spc_de = ReadDirExtended(spc_dir, "pg_tblspc", LOG)) != NULL)
 	{
 		if (strcmp(spc_de->d_name, ".") == 0 ||
 			strcmp(spc_de->d_name, "..") == 0)
@@ -3055,18 +3059,8 @@ RemovePgTempFilesInDir(const char *tmpdirname, bool unlink_all)
 	char		rm_path[MAXPGPATH * 2];
 
 	temp_dir = AllocateDir(tmpdirname);
-	if (temp_dir == NULL)
-	{
-		/* anything except ENOENT is fishy */
-		if (errno != ENOENT)
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not open directory \"%s\": %m",
-							tmpdirname)));
-		return;
-	}
 
-	while ((temp_de = ReadDir(temp_dir, tmpdirname)) != NULL)
+	while ((temp_de = ReadDirExtended(temp_dir, tmpdirname, LOG)) != NULL)
 	{
 		if (strcmp(temp_de->d_name, ".") == 0 ||
 			strcmp(temp_de->d_name, "..") == 0)
@@ -3082,22 +3076,38 @@ RemovePgTempFilesInDir(const char *tmpdirname, bool unlink_all)
 		{
 			struct stat statbuf;
 
-			/* note that we ignore any error here and below */
 			if (lstat(rm_path, &statbuf) < 0)
+			{
+				ereport(LOG,
+						(errcode_for_file_access(),
+						 errmsg("could not stat file \"%s\": %m", rm_path)));
 				continue;
+			}
 
 			if (S_ISDIR(statbuf.st_mode))
 			{
+				/* recursively remove contents, then directory itself */
 				RemovePgTempFilesInDir(rm_path, true);
-				rmdir(rm_path);
+
+				if (rmdir(rm_path) < 0)
+					ereport(LOG,
+							(errcode_for_file_access(),
+							 errmsg("could not remove directory \"%s\": %m",
+									rm_path)));
 			}
 			else
-				unlink(rm_path);
+			{
+				if (unlink(rm_path) < 0)
+					ereport(LOG,
+							(errcode_for_file_access(),
+							 errmsg("could not remove file \"%s\": %m",
+									rm_path)));
+			}
 		}
 		else
-			elog(LOG,
-				 "unexpected file found in temporary-files directory: \"%s\"",
-				 rm_path);
+			ereport(LOG,
+					(errmsg("unexpected file found in temporary-files directory: \"%s\"",
+							rm_path)));
 	}
 
 	FreeDir(temp_dir);
@@ -3112,29 +3122,15 @@ RemovePgTempRelationFiles(const char *tsdirname)
 	char		dbspace_path[MAXPGPATH * 2];
 
 	ts_dir = AllocateDir(tsdirname);
-	if (ts_dir == NULL)
-	{
-		/* anything except ENOENT is fishy */
-		if (errno != ENOENT)
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not open directory \"%s\": %m",
-							tsdirname)));
-		return;
-	}
 
-	while ((de = ReadDir(ts_dir, tsdirname)) != NULL)
+	while ((de = ReadDirExtended(ts_dir, tsdirname, LOG)) != NULL)
 	{
-		int			i = 0;
-
 		/*
 		 * We're only interested in the per-database directories, which have
 		 * numeric names.  Note that this code will also (properly) ignore "."
 		 * and "..".
 		 */
-		while (isdigit((unsigned char) de->d_name[i]))
-			++i;
-		if (de->d_name[i] != '\0' || i == 0)
+		if (strspn(de->d_name, "0123456789") != strlen(de->d_name))
 			continue;
 
 		snprintf(dbspace_path, sizeof(dbspace_path), "%s/%s",
@@ -3163,7 +3159,11 @@ RemovePgTempRelationFilesInDbspace(const char *dbspacedirname)
 		snprintf(rm_path, sizeof(rm_path), "%s/%s",
 				 dbspacedirname, de->d_name);
 
-		unlink(rm_path);		/* note we ignore any error */
+		if (unlink(rm_path) < 0)
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not remove file \"%s\": %m",
+							rm_path)));
 	}
 
 	FreeDir(dbspace_dir);