[LU-3344] Add open_by_handle() syscall for Lustre clients

• Type: New Feature
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.6.0
• Labels: patch
• Assignee: Jian Yu
• Reporter: Andreas Dilger

Description

The open_by_handle_at() and name_to_handle() functions were added to Linux 2.6.38, and allow opening files by a file handle instead of path traversal. This may be useful for HPC applications to reduce loading on the metadata server from repeated path traversal.

There is some chance this feature already works on Lustre, due to the re-use of the NFS exportfs_encode_fh() and exportfs_decode_fh() functions. This code needs a regression test in Lustre to verify it is working correctly, along with documentation in the user manual.

Issue Links

• is related to: LU-3717 Kernel panic in ll_encode_fh() while testing file handle syscalls on FC18 client

Comments

[Peter Jones]

Fixed in 2.6

[James A Simmons]

The last patch http://review.whamcloud.com/#/c/7247 has been merged. This ticket can be closed.

[James A Simmons]

Patch http://review.whamcloud.com/#/c/7247 has been updated and tested.

[root@spoon46 tests]# ./check_fhandle_syscalls temp-file /lustre/barry
fh_bytes: 32
fh_type: 151
fh_data: 0 4 0 0 2 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
check_fhandle_syscalls test Passed!

[James A Simmons]

I updated the patch. Even tho I was testing with a 3.11 kernel I couldn't get this to work but then I realized the kernel has to be configured with CONFIG_FHANDLE so I updated the autoconf test to handle this case. I also removed the FC18 condition for the sanity test since this is not the case for me.

[Peter Jones]

Yu, Jian will take over ensuring that this patch lands

[Peter Jones]

Bobbie

Could you please review and take care of this patch?

Thanks

Peter

[Swapnil Pimpale (Inactive)]

As noted in the ticket description the syscalls and the structure file_handle were added in Linux kernel 2.6.39

I have added a config time check which checks whether file_handle, name_to_handle_at() and open_by_handle_at() can be resolved.
I expect this patch (http://review.whamcloud.com/#/c/7247/5) to solve the build errors on targets where these syscalls aren't supported.

[Swapnil Pimpale (Inactive)]

While testing these syscalls on FC18 client, I hit this (https://jira.hpdd.intel.com/browse/LU-3717) panic in ll_enocde_fh()

[Swapnil Pimpale (Inactive)]

Please note that the above patch (http://review.whamcloud.com/#/c/7129/) is abandoned.

I have added a new patch here (http://review.whamcloud.com/#/c/7247/)
As mentioned in the previous comment, these syscalls are supported in glibc >= 2.14
So currently this test is run only on FC18 clients which have 2.16 glibc and skipped otherwise.

[Gaurav Mahajan (Inactive)]

Status : Work In Progress

Here is the initial patch for sanity tests to check 'name_to_handle_at' and 'open_by_handle_at' syscalls.
http://review.whamcloud.com/#/c/7129/

Currently the patch is incomplete because 'name_to_handle_at' and 'open_by_handle_at' are updated in glibc 2.14. Current Glibc version is 2.12. So for now we are calling the syscalls with syscall numbers directly.