linux-kernel - [RFC] FS_IOC

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Date:	Tue, 20 Jul 2010 16:48:26 -0700 (PDT)
From:	Sage Weil <sage@...dream.net>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC] FS_IOC_SYNCFS

As far as I can see, currently the only way to sync a single file system 
(and not _all_ mounted file systems) is via the BLKFLSBUF ioctl, which 
will sync_filesystem() and then invalidate_bdev().  If you _just_ want to 
sync, though, the invalidate_bdev() is unnecessary and potentially 
counter-productive.

Would it be reasonable to add a simple call like so?  Then you could

	fd = open("/path/for/some/mount", O_RDONLY);
	ioctl(fd, FS_IOC_SYNCFS);
	close(fd);

or something along those lines.
sage


diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2d140a7..0bc9f7a 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -593,6 +593,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 	case FS_IOC_FIEMAP:
 		return ioctl_fiemap(filp, arg);
 
+	case FS_IOC_SYNCFS:
+		return sync_filesystem(filp->f_dentry->d_sb);
+
 	case FIGETBSZ:
 	{
 		struct inode *inode = filp->f_path.dentry->d_inode;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 471e1ff..4a84d78 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -321,6 +321,7 @@ struct inodes_stat_t {
 #define	FS_IOC_GETVERSION		_IOR('v', 1, long)
 #define	FS_IOC_SETVERSION		_IOW('v', 2, long)
 #define FS_IOC_FIEMAP			_IOWR('f', 11, struct fiemap)
+#define FS_IOC_SYNCFS                   _IO('S', 12)
 #define FS_IOC32_GETFLAGS		_IOR('f', 1, int)
 #define FS_IOC32_SETFLAGS		_IOW('f', 2, int)
 #define FS_IOC32_GETVERSION		_IOR('v', 1, int)
--
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