From: Bin Meng <bmeng@tinylab.org>
To: Jason Wang <jasowang@redhat.com>, qemu-devel@nongnu.org
Cc: Zhangjin Wu <falcon@tinylab.org>
Subject: [PATCH] net: tap: Drop the close of fds for child process
Date: Thu, 6 Apr 2023 19:20:41 +0800 [thread overview]
Message-ID: <20230406112041.798585-1-bmeng@tinylab.org> (raw)
Current codes using a brute-force traversal of all file descriptors
do not scale on a system where the maximum number of file descriptors
are set to a very large value (e.g.: in a Docker container of Manjaro
distribution it is set to 1073741816). QEMU just looks freezed during
start-up.
The close-on-exec flag was introduced since a faily old Linux kernel
(2.6.23). With recent newer kernels that QEMU supports, we don't need
to manually close the fds for child process as the proper O_CLOEXEC
flag should have been set properly on files that we don't want child
process to see.
Reported-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Bin Meng <bmeng@tinylab.org>
---
net/tap.c | 14 --------------
1 file changed, 14 deletions(-)
diff --git a/net/tap.c b/net/tap.c
index 1bf085d422..49e1915484 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -446,13 +446,6 @@ static void launch_script(const char *setup_script, const char *ifname,
return;
}
if (pid == 0) {
- int open_max = sysconf(_SC_OPEN_MAX), i;
-
- for (i = 3; i < open_max; i++) {
- if (i != fd) {
- close(i);
- }
- }
parg = args;
*parg++ = (char *)setup_script;
*parg++ = (char *)ifname;
@@ -536,17 +529,10 @@ static int net_bridge_run_helper(const char *helper, const char *bridge,
return -1;
}
if (pid == 0) {
- int open_max = sysconf(_SC_OPEN_MAX), i;
char *fd_buf = NULL;
char *br_buf = NULL;
char *helper_cmd = NULL;
- for (i = 3; i < open_max; i++) {
- if (i != sv[1]) {
- close(i);
- }
- }
-
fd_buf = g_strdup_printf("%s%d", "--fd=", sv[1]);
if (strrchr(helper, ' ') || strrchr(helper, '\t')) {
--
2.34.1
next reply other threads:[~2023-04-06 11:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-06 11:20 Bin Meng [this message]
2023-04-06 12:34 ` [PATCH] net: tap: Drop the close of fds for child process Philippe Mathieu-Daudé
2023-04-06 12:44 ` Bin Meng
2023-04-18 8:55 ` Daniel P. Berrangé
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230406112041.798585-1-bmeng@tinylab.org \
--to=bmeng@tinylab.org \
--cc=falcon@tinylab.org \
--cc=jasowang@redhat.com \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).