[LU-137] ioctl passthrough mechanism for Lustre OST/MDT mountpoints

• Type: New Feature
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0
• Affects Version/s: Lustre 2.1.0, Lustre 2.5.0
• Labels: patch
• Bugzilla ID: 14,489
• Assignee: Andreas Dilger
• Reporter: Andreas Dilger

Description

Implement an interface for sending IO Control (ioctl) commands from userspace through the Lustre mount point to the underlying ldiskfs filesystem to allow execution of filesystem-wide ioctl() commands, such as resize. This will allow user-space tools that operate via ioctl() commands on the filesystem mountpoint to be used on the Lustre MDT and OST filesystems while they are mounted and in use subject to any limitations of the original ioctl() commands themselves.

Issue Links

• is related to: LU-5822 health_check file not updating properly
• is related to: LU-4795 server_put_mount() calls server_deregister_mount() even if this isn't the last reference
• is related to: LU-8151 OST/MDT /proc/mounts always shows "ro" for server mountpoints
• is related to: LU-16835 lustre-initialization: Operation not supported while trying to set fs label, tune2fs 1.47.0-wc1
• is related to: LU-4931 New feature of giving server/storage side advice of accessing file
• is related to: LU-17027 missing #include <linux/file.h> in lustre/target/tgt_mount.c
• is related to: LU-6202 clean up ioctl handling
• is related to: LU-11355 Add Lustre trim support

Comments

[Swapnil Pimpale (Inactive)]

Hi Andeas,

I have ported the ioctl_passthru-1_8.patch to the latest master.
With this patch I tested EXT4_IOC_GETFLAGS and EXT4_IOC_GETVERSION ioctls on OST and MDT mountpoints. These ioctls work and return expected values.
I have added this a testcase in sanity.sh
The patch can be found here -> http://review.whamcloud.com/#/c/7354/

I tried the EXT4_IOC_SETVERSION ioctl but that resulted in a crash.
Is that expected?

[Andreas Dilger]

Unfortunately, I expect that the 1.8 version of the patch is completely useless for the current 2.1 and master code...

You might want to experiment with some simple ioctl (e.g. EXT4_IOC_GETFLAGS or EXT4_IOC_GETVERSION) to get that working before you try to have resize2fs calling the online resizer. The end goal is that at least EXT4_IOC_GROUP_EXTEND/EXT4_IOC_GROUP_ADD (old resize), EXT4_IOC_RESIZE_FS (new resize), and FITRIM work.

[Kalpak Shah (Inactive)]

Hi Andreas, I am working on this ticket.

[Andreas Dilger]

Updated patch that includes sb->s_dev fix.

[Andreas Dilger]

Patch for the e2fsprogs resize2fs tool to allow it to specify the directory mountpoint for resizing, instead of requiring one to specify a block device for the resize operation.

I don't think this should be required for the ioctl passthrough to work, but it simplifies the usage of resize2fs, and I thought I needed it until I fixed the Lustre sb->s_dev on the mounted filesystem.

[Andreas Dilger]

Prototype patch for ioctl passthrough. It is known to have problems (i.e. crash if used), but is close to what I think would work.

There are a few avenues for investigation as to why it is not working:

• I had to make a change to the e2fsprogs library to allow resize2fs to work,
  because it was calling stat() on the mountpoint to verify that it was the
  same as the underlying block device, to determine if the filesystem is mounted.
  (first attachment)
• This in turn required a change to the lustre server mountpoint to ensure that
  it is initializing the device number correctly, so that st_rdev for the Lustre
  mountpoint is the same as st_dev of the underlying device node. This is also
  included with the server_ioctl() function that is supposed to be working.
  (second attachment)

• the pointer to the underlying ldiskfs device may be incorrect. The handling
  of the internal ldiskfs mountpoint is more complex than I'd like, so it isn't
  immediately clear that my code is pointing at the right device
• the size of the ioctl parameter that is being copied could be incorrect

[Bryon Neitzel (Inactive)]

Assigning back to Andreas until we find a new owner for this project.