linux-kernel - Re: [PATCH] fs: add the FIGETFROZEN ioctl call

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Date:	Thu, 14 Apr 2016 10:10:41 +0200
From:	Florian Margaine <florian@...gaine.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: add the FIGETFROZEN ioctl call

Hi,

For some reason, my email client replaced tabs with spaces in my
previous email.

Here is the patch using another client.

Regards,
Florian


>From 80febe62cf5c21e0a369b64e38c82f068a416a61 Mon Sep 17 00:00:00 2001
From: Florian MARGAINE <florian@...gaine.com>
Date: Sat, 19 Mar 2016 23:25:28 +0100
Subject: [PATCH] fs: add the FIGETFROZEN ioctl call

This lets userland get the filesystem freezing status, aka whether the
filesystem is frozen or not. This is so that an application can know if
it should freeze the filesystem or if it isn't necessary when taking a
snapshot.
---
 fs/compat_ioctl.c       |  1 +
 fs/ioctl.c              | 13 +++++++++++++
 include/uapi/linux/fs.h |  1 +
 3 files changed, 15 insertions(+)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index bd01b92..d2173ab 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -918,6 +918,7 @@ COMPATIBLE_IOCTL(FIGETBSZ)
 COMPATIBLE_IOCTL(FIFREEZE)
 COMPATIBLE_IOCTL(FITHAW)
 COMPATIBLE_IOCTL(FITRIM)
+COMPATIBLE_IOCTL(FIGETFROZEN)
 COMPATIBLE_IOCTL(KDGETKEYCODE)
 COMPATIBLE_IOCTL(KDSETKEYCODE)
 COMPATIBLE_IOCTL(KDGKBTYPE)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 116a333..249ed20 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -568,6 +568,16 @@ static int ioctl_fsthaw(struct file *filp)
 	return thaw_super(sb);
 }
 
+static int ioctl_fsgetfrozen(struct file *filp)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	return sb->s_writers.frozen;
+}
+
 static long ioctl_file_dedupe_range(struct file *file, void __user
*arg)
 {
 	struct file_dedupe_range __user *argp = arg;
@@ -652,6 +662,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int
fd, unsigned int cmd,
 		error = ioctl_fsthaw(filp);
 		break;
 
+	case FIGETFROZEN:
+		return put_user(ioctl_fsgetfrozen(filp), argp);
+
 	case FS_IOC_FIEMAP:
 		return ioctl_fiemap(filp, arg);
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 149bec8..d48f19c 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -230,6 +230,7 @@ struct fsxattr {
 #define FIFREEZE	_IOWR('X', 119, int)	/* Freeze */
 #define FITHAW		_IOWR('X', 120, int)	/* Thaw */
 #define FITRIM		_IOWR('X', 121, struct fstrim_range)	
/* Trim */
+#define FIGETFROZEN	_IOWR('X', 122, int)	/* Frozen
status */
 #define FICLONE		_IOW(0x94, 9, int)
 #define FICLONERANGE	_IOW(0x94, 13, struct file_clone_range)
 #define FIDEDUPERANGE	_IOWR(0x94, 54, struct file_dedupe_range)
-- 
2.8.0