From: Karel Zak <kzak@redhat.com>
Date: Thu, 30 Sep 2021 09:11:30 +0000 (+0200)
Subject: lsfd: optimize symlinks use
X-Git-Tag: v2.38-rc1~144^2~82
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b813e8ce8f0375ce7f8b3f0deb8f51f8af5d333f;p=thirdparty%2Futil-linux.git

lsfd: optimize symlinks use

Like the previous commit, this patch tries to reuse
/proc/#/{fd,ns,cwd,root} symlinks if possible. On my machine it
saves ~2000 stat() calls.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/misc-utils/lsfd.c b/misc-utils/lsfd.c
index 5c4cb17c4c..f855f637cb 100644
--- a/misc-utils/lsfd.c
+++ b/misc-utils/lsfd.c
@@ -351,16 +351,27 @@ static struct file *collect_file_symlink(struct path_cxt *pc,
 {
 	char sym[PATH_MAX] = { '\0' };
 	struct stat sb;
-	struct file *f;
+	struct file *f, *prev;
 
-	if (ul_path_stat(pc, &sb, 0, name) < 0)
-		return NULL;
 	if (ul_path_readlink(pc, sym, sizeof(sym), name) < 0)
 		return NULL;
 
-	f = new_file(proc, stat2class(&sb));
+	/* The /proc/#/{fd,ns} often contains the same file (e.g. /dev/tty)
+	 * more than once. Let's try to reuse the previous file if the real
+	 * path is the same to save stat() call.
+	 */
+	prev = list_last_entry(&proc->files, struct file, files);
+	if (prev && prev->name && strcmp(prev->name, sym) == 0) {
+		f = copy_file(prev);
+		f->association = assoc;
+	} else {
+		if (ul_path_stat(pc, &sb, 0, name) < 0)
+			return NULL;
+
+		f = new_file(proc, stat2class(&sb));
+		file_set_path(f, &sb, sym, assoc);
+	}
 
-	file_set_path(f, &sb, sym, assoc);
 	file_init_content(f);
 
 	if (is_association(f, EXE))