linux-kernel - [PATCH 3/4] fs: Add F_DUPFD

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Message-ID: <20200420071548.62112-4-nate.karstens@garmin.com>
Date:   Mon, 20 Apr 2020 02:15:47 -0500
From:   Nate Karstens <nate.karstens@...min.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...nel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Arnd Bergmann <arnd@...db.de>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linux-alpha@...r.kernel.org>, <linux-parisc@...r.kernel.org>,
        <sparclinux@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Changli Gao <xiaosuo@...il.com>,
        Nate Karstens <nate.karstens@...min.com>
Subject: [PATCH 3/4] fs: Add F_DUPFD_CLOFORK to fcntl(2)

Implement functionality for duplicating a file descriptor
and having the close-on-fork flag automatically set in the
new file descriptor.

Signed-off-by: Nate Karstens <nate.karstens@...min.com>
---
 fs/fcntl.c                       | 4 ++++
 include/uapi/linux/fcntl.h       | 3 +++
 tools/include/uapi/linux/fcntl.h | 3 +++
 3 files changed, 10 insertions(+)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index b59b27c3a338..43ca3e3dacc5 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -333,6 +333,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 	case F_DUPFD_CLOEXEC:
 		err = f_dupfd(arg, filp, O_CLOEXEC);
 		break;
+	case F_DUPFD_CLOFORK:
+		err = f_dupfd(arg, filp, O_CLOFORK);
+		break;
 	case F_GETFD:
 		err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 		err |= get_close_on_fork(fd) ? FD_CLOFORK : 0;
@@ -439,6 +442,7 @@ static int check_fcntl_cmd(unsigned cmd)
 	switch (cmd) {
 	case F_DUPFD:
 	case F_DUPFD_CLOEXEC:
+	case F_DUPFD_CLOFORK:
 	case F_GETFD:
 	case F_SETFD:
 	case F_GETFL:
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index ca88b7bce553..9e1069ff3a22 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -55,6 +55,9 @@
 #define F_GET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 13)
 #define F_SET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 14)
 
+/* Create a file descriptor with FD_CLOFORK set. */
+#define F_DUPFD_CLOFORK	(F_LINUX_SPECIFIC_BASE + 15)
+
 /*
  * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be
  * used to clear any hints previously set.
diff --git a/tools/include/uapi/linux/fcntl.h b/tools/include/uapi/linux/fcntl.h
index ca88b7bce553..9e1069ff3a22 100644
--- a/tools/include/uapi/linux/fcntl.h
+++ b/tools/include/uapi/linux/fcntl.h
@@ -55,6 +55,9 @@
 #define F_GET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 13)
 #define F_SET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 14)
 
+/* Create a file descriptor with FD_CLOFORK set. */
+#define F_DUPFD_CLOFORK	(F_LINUX_SPECIFIC_BASE + 15)
+
 /*
  * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be
  * used to clear any hints previously set.
-- 
2.26.1