On 2024/8/27 10:13, Darrick J. Wong wrote:
On Tue, Aug 27, 2024 at 01:41:08AM +0000, Hongbo Li wrote:
Many mainstream file systems already support the GETVERSION ioctl,
and their implementations are completely the same, essentially
just obtain the value of i_generation. We think this ioctl can be
implemented at the VFS layer, so the file systems do not need to
implement it individually.
What if a filesystem never touches i_generation? Is it ok to advertise
a generation number of zero when that's really meaningless? Or should
we gate the generic ioctl on (say) whether or not the fs implements file
handles and/or supports nfs?
This ioctl mainly returns the i_generation, and whether it has meaning
is up to the specific file system. Some tools will invoke
IOC_GETVERSION, such as `lsattr -v`(but if it's lattr, it won't), but
users may not necessarily actually use this value.
Thanks,
Hongbo
--D
Signed-off-by: Hongbo Li <lihongbo22@xxxxxxxxxx>
---
fs/ioctl.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 64776891120c..dff887ec52c4 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -878,6 +878,9 @@ static int do_vfs_ioctl(struct file *filp, unsigned int fd,
case FS_IOC_GETFSUUID:
return ioctl_getfsuuid(filp, argp);
+ case FS_IOC_GETVERSION:
+ return put_user(inode->i_generation, (int __user *)argp);
+
case FS_IOC_GETFSSYSFSPATH:
return ioctl_get_fs_sysfs_path(filp, argp);
@@ -992,6 +995,9 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd,
cmd = (cmd == FS_IOC32_GETFLAGS) ?
FS_IOC_GETFLAGS : FS_IOC_SETFLAGS;
fallthrough;
+ case FS_IOC32_GETVERSION:
+ cmd = FS_IOC_GETVERSION;
+ fallthrough;
/*
* everything else in do_vfs_ioctl() takes either a compatible
* pointer argument or no argument -- call it with a modified
--
2.34.1
