From patchwork Sat Nov 9 07:50:12 2019
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
X-Patchwork-Submitter: Piotr Sarna
X-Patchwork-Id: 11235817
Return-Path:
Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org
[172.30.200.123])
by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8705E1864
for ;
Sat, 9 Nov 2019 07:50:29 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
by mail.kernel.org (Postfix) with ESMTP id 7050421D7F
for ;
Sat, 9 Nov 2019 07:50:28 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
id S1726390AbfKIHuZ (ORCPT
);
Sat, 9 Nov 2019 02:50:25 -0500
Received: from mx-out.tlen.pl ([193.222.135.158]:55625 "EHLO mx-out.tlen.pl"
rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
id S1726374AbfKIHuZ (ORCPT );
Sat, 9 Nov 2019 02:50:25 -0500
Received: (wp-smtpd smtp.tlen.pl 37743 invoked from network);
9 Nov 2019 08:50:22 +0100
Received: from unknown (HELO sarna-pc.localdomain)
(p.sarna@o2.pl@[12.207.198.221])
(envelope-sender )
by smtp.tlen.pl (WP-SMTPD) with ECDHE-RSA-AES256-GCM-SHA384
encrypted SMTP
for ; 9 Nov 2019 08:50:22 +0100
From: Piotr Sarna
To: mike.kravetz@oracle.com, linux-kernel@vger.kernel.org
Cc: Piotr Sarna , linux-mm@kvack.org,
viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
mhocko@kernel.org,
syzbot+136d2439a4e6561ea00c@syzkaller.appspotmail.com
Subject: [PATCH v2] hugetlbfs: add O_TMPFILE support
Date: Sat, 9 Nov 2019 08:50:12 +0100
Message-Id:
X-Mailer: git-send-email 2.23.0
MIME-Version: 1.0
X-WP-MailID: 939dbc952ae583a528cb1dffcdafb309
X-WP-AV: skaner antywirusowy Poczty o2
X-WP-SPAM: NO 0000000 [EdON]
Sender: linux-fsdevel-owner@vger.kernel.org
Precedence: bulk
List-ID:
X-Mailing-List: linux-fsdevel@vger.kernel.org
With hugetlbfs, a common pattern for mapping anonymous huge pages
is to create a temporary file first. Currently libraries like
libhugetlbfs and seastar create these with a standard mkstemp+unlink
trick, but it would be more robust to be able to simply pass
the O_TMPFILE flag to open(). O_TMPFILE is already supported by several
file systems like ext4 and xfs. The implementation simply uses the existing
d_tmpfile utility function to instantiate the dcache entry for the file.
Tested manually by successfully creating a temporary file by opening
it with (O_TMPFILE|O_RDWR) on mounted hugetlbfs and successfully
mapping 2M huge pages with it. Without the patch, trying to open
a file with O_TMPFILE results in -ENOSUP.
v2 changes:
* syzkaller thankfully discovered a bug during unmount - tmpfile
erroneously called dget() on a dentry when creating a tmpfile,
and it was never countered by a dput(), because tmpfile is never
explicitly unlinked. In v2, dget() is simply not called for tmpfile.
Verified manually, and also with the reproducer provided by syzkaller.
Reported-by: syzbot+136d2439a4e6561ea00c@syzkaller.appspotmail.com
Signed-off-by: Piotr Sarna
Reviewed-by: Mike Kravetz
---
fs/hugetlbfs/inode.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a478df035651..a39d7a0a158e 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -815,8 +815,11 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
/*
* File creation. Allocate an inode, and we're done..
*/
-static int hugetlbfs_mknod(struct inode *dir,
- struct dentry *dentry, umode_t mode, dev_t dev)
+static int do_hugetlbfs_mknod(struct inode *dir,
+ struct dentry *dentry,
+ umode_t mode,
+ dev_t dev,
+ bool tmpfile)
{
struct inode *inode;
int error = -ENOSPC;
@@ -824,13 +827,23 @@ static int hugetlbfs_mknod(struct inode *dir,
inode = hugetlbfs_get_inode(dir->i_sb, dir, mode, dev);
if (inode) {
dir->i_ctime = dir->i_mtime = current_time(dir);
- d_instantiate(dentry, inode);
- dget(dentry); /* Extra count - pin the dentry in core */
+ if (tmpfile) {
+ d_tmpfile(dentry, inode);
+ } else {
+ d_instantiate(dentry, inode);
+ dget(dentry);/* Extra count - pin the dentry in core */
+ }
error = 0;
}
return error;
}
+static int hugetlbfs_mknod(struct inode *dir,
+ struct dentry *dentry, umode_t mode, dev_t dev)
+{
+ return do_hugetlbfs_mknod(dir, dentry, mode, dev, false);
+}
+
static int hugetlbfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
@@ -844,6 +857,12 @@ static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, umode_t mo
return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);
}
+static int hugetlbfs_tmpfile(struct inode *dir,
+ struct dentry *dentry, umode_t mode)
+{
+ return do_hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0, true);
+}
+
static int hugetlbfs_symlink(struct inode *dir,
struct dentry *dentry, const char *symname)
{
@@ -1102,6 +1121,7 @@ static const struct inode_operations hugetlbfs_dir_inode_operations = {
.mknod = hugetlbfs_mknod,
.rename = simple_rename,
.setattr = hugetlbfs_setattr,
+ .tmpfile = hugetlbfs_tmpfile,
};
static const struct inode_operations hugetlbfs_inode_operations = {