Skip unnecessary stat() calls in walkdir().

Some kernels can tell us the type of a "dirent", so we can avoid a call
to stat() or lstat() in many cases.  Define a new function
get_dirent_type() to contain that logic, for use by the backend and
frontend versions of walkdir(), and perhaps other callers in future.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BFzxupGGN4GpUdbzZN%2Btn6FQPHo8w0Q%2BAPH5Wz8RG%2Bww%40mail.gmail.com

1 files changed, 16 insertions, 17 deletions

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index f376a97ed67..bd72a87ee30 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -89,6 +89,7 @@
 #include "access/xlog.h"
 #include "catalog/pg_tablespace.h"
 #include "common/file_perm.h"
+#include "common/file_utils.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "portability/mem.h"
@@ -3340,8 +3341,6 @@ walkdir(const char *path,
 	while ((de = ReadDirExtended(dir, path, elevel)) != NULL)
 	{
 		char		subpath[MAXPGPATH * 2];
-		struct stat fst;
-		int			sret;
 
 		CHECK_FOR_INTERRUPTS();
 
@@ -3351,23 +3350,23 @@ walkdir(const char *path,
 
 		snprintf(subpath, sizeof(subpath), "%s/%s", path, de->d_name);
 
-		if (process_symlinks)
-			sret = stat(subpath, &fst);
-		else
-			sret = lstat(subpath, &fst);
-
-		if (sret < 0)
+		switch (get_dirent_type(subpath, de, process_symlinks, elevel))
 		{
-			ereport(elevel,
-					(errcode_for_file_access(),
-					 errmsg("could not stat file \"%s\": %m", subpath)));
-			continue;
-		}
+			case PGFILETYPE_REG:
+				(*action) (subpath, false, elevel);
+				break;
+			case PGFILETYPE_DIR:
+				walkdir(subpath, action, false, elevel);
+				break;
+			default:
 
-		if (S_ISREG(fst.st_mode))
-			(*action) (subpath, false, elevel);
-		else if (S_ISDIR(fst.st_mode))
-			walkdir(subpath, action, false, elevel);
+				/*
+				 * Errors are already reported directly by get_dirent_type(),
+				 * and any remaining symlinks and unknown file types are
+				 * ignored.
+				 */
+				break;
+		}
 	}
 
 	FreeDir(dir);				/* we ignore any error here */