Fix memory leak in BufFileCreateShared().

Also this commit unifies some duplicated code in makeBufFile() and
BufFileOpenShared() into new function makeBufFileCommon().

Author: Antonin Houska
Reviewed-By: Thomas Munro, Tatsuo Ishii
Discussion: https://postgr.es/m/16139.1529049566%40localhost

src/backend/storage/file/buffile.c

@@ -99,6 +99,7 @@ struct BufFile
 	char		buffer[BLCKSZ];
 };
 
+static BufFile *makeBufFileCommon(int nfiles);
 static BufFile *makeBufFile(File firstfile);
 static void extendBufFile(BufFile *file);
 static void BufFileLoadBuffer(BufFile *file);
@@ -106,21 +107,16 @@ static void BufFileDumpBuffer(BufFile *file);
 static int	BufFileFlush(BufFile *file);
 static File MakeNewSharedSegment(BufFile *file, int segment);
 
-
 /*
- * Create a BufFile given the first underlying physical file.
- * NOTE: caller must set isInterXact if appropriate.
+ * Create BufFile and perform the common initialization.
  */
 static BufFile *
-makeBufFile(File firstfile)
+makeBufFileCommon(int nfiles)
 {
 	BufFile    *file = (BufFile *) palloc(sizeof(BufFile));
 
-	file->numFiles = 1;
-	file->files = (File *) palloc(sizeof(File));
-	file->files[0] = firstfile;
-	file->offsets = (off_t *) palloc(sizeof(off_t));
-	file->offsets[0] = 0L;
+	file->numFiles = nfiles;
+	file->offsets = (off_t *) palloc0(sizeof(off_t) * nfiles);
 	file->isInterXact = false;
 	file->dirty = false;
 	file->resowner = CurrentResourceOwner;
@@ -128,6 +124,21 @@ makeBufFile(File firstfile)
 	file->curOffset = 0L;
 	file->pos = 0;
 	file->nbytes = 0;
+
+	return file;
+}
+
+/*
+ * Create a BufFile given the first underlying physical file.
+ * NOTE: caller must set isInterXact if appropriate.
+ */
+static BufFile *
+makeBufFile(File firstfile)
+{
+	BufFile    *file = makeBufFileCommon(1);
+
+	file->files = (File *) palloc(sizeof(File));
+	file->files[0] = firstfile;
 	file->readOnly = false;
 	file->fileset = NULL;
 	file->name = NULL;
@@ -246,23 +257,12 @@ BufFileCreateShared(SharedFileSet *fileset, const char *name)
 {
 	BufFile    *file;
 
-	file = (BufFile *) palloc(sizeof(BufFile));
+	file = makeBufFileCommon(1);
 	file->fileset = fileset;
 	file->name = pstrdup(name);
-	file->numFiles = 1;
 	file->files = (File *) palloc(sizeof(File));
 	file->files[0] = MakeNewSharedSegment(file, 0);
-	file->offsets = (off_t *) palloc(sizeof(off_t));
-	file->offsets[0] = 0L;
-	file->isInterXact = false;
-	file->dirty = false;
-	file->resowner = CurrentResourceOwner;
-	file->curFile = 0;
-	file->curOffset = 0L;
-	file->pos = 0;
-	file->nbytes = 0;
 	file->readOnly = false;
-	file->name = pstrdup(name);
 
 	return file;
 }
@@ -283,7 +283,6 @@ BufFileOpenShared(SharedFileSet *fileset, const char *name)
 	File	   *files;
 	int			nfiles = 0;
 
-	file = (BufFile *) palloc(sizeof(BufFile));
 	files = palloc(sizeof(File) * capacity);
 
 	/*
@@ -317,16 +316,8 @@ BufFileOpenShared(SharedFileSet *fileset, const char *name)
 				(errcode_for_file_access(),
 				 errmsg("could not open BufFile \"%s\"", name)));
 
-	file->numFiles = nfiles;
+	file = makeBufFileCommon(nfiles);
 	file->files = files;
-	file->offsets = (off_t *) palloc0(sizeof(off_t) * nfiles);
-	file->isInterXact = false;
-	file->dirty = false;
-	file->resowner = CurrentResourceOwner;	/* Unused, can't extend */
-	file->curFile = 0;
-	file->curOffset = 0L;
-	file->pos = 0;
-	file->nbytes = 0;
 	file->readOnly = true;		/* Can't write to files opened this way */
 	file->fileset = fileset;
 	file->name = pstrdup(name);