[LU-10934] integrate statx() API with Lustre

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0
• Labels: medium
• Assignee: Qian Yingjin
• Reporter: Andreas Dilger

Description

Kernels 4.10 and later (since commit a528d35e8b) have an enhanced statx() interface that can specify a bitmask to fetch specific attributes from a file (e.g. st_uid, st_gid, st_mode, and st_btime == file creation time), rather than fetching all of the normal stat() attributes (such as st_size and st_blocks). It also has a AT_STATX_DONT_SYNC mode which allows the kernel to return "lazy" stats without flushing all of the client data and fetching an accurate result from the server.

This matches (not coincidentally) very well with the Lustre attribute mechanism, and could be advantageous for fetching attributes from ls --color (needs st_mode) without having to do a glimpse to fetch the size (which is just discarded anyway).

The Lustre patch https://review.whamcloud.com/27715 "LU-9558 llite: user enhanced getattr functionality in newer kernels" added very basic support for this interface, but it only went so far as to handle the kernel API changes, but doesn't actually handle the different attribute flags appropriately (it currently fetches and returns all normal attributes - STATX_BASIC_STATS). This interface should be wired up properly so that we can take advantage of the efficiencies available.

• only fetch MDS attributes if STATX_SIZE and STATX_BLOCKS are not requested, and avoid OSS glimpse RPCs completely
• hook this into statahead to avoid async glimpse locks (AGL) if OST information not needed
• enhance the MDS RPC interface to return the file creation time stored in both ldiskfs and ZFS already, and enable STATX_BTIME
• in conjunction with Lazy Size-on-MDT (LSOM, LU-9538) return the LSOM size if AT_STATX_DONT_SYNC is used

Issue Links

• is related to: LU-11987 sanity test 59 fails with “test_59 failed with 1”
• is related to: LU-13628 sanityn test_106a test_106c: supported stx_attributes: got ''?'', expected ''30''
• is related to: LU-13826 fix compatibility for LL_IOC_MDC_GETINFO
• is related to: LU-10560 Fixes for 4.14 kernel
• is related to: LU-10805 fixes for 4.15 kernel
• is related to: LU-11916 LSOM: lazy_stat mount option not recognized
• is related to: LU-13148 Interop: sanity test 56ra fails with ''/usr/bin/lfs find -size 0 -type f -lazy /mnt/lustre/d56ra.sanity' should not send glimpse RPCs to OST'
• is related to: LU-13753 sanityn test_51b: 'file size is 1024, should be 3145728'
• is related to: LU-12480 add STATX_PROJID to upstream kernel
• is related to: LU-9558 Support linux kernel version 4.12
• is related to: LU-11554 Make stat() work with LSOM
• is related to: LU-11971 Send file creation time to clients
• is related to: LU-12332 Add a liblustreapi call for IOC_MDC_GETFILEINFO
• is related to: LU-9538 Size on MDT with guarantee of eventual consistency
• is related to: LU-1158 nanosecond timestamp support for Lustre

Comments

[Alex Zhuravlev]

tests sanityn/106* seem to be broken - even recent debugfs doesn't dump "btime".
probably crtime was meant?

[Peter Jones]

Landed for 2.14

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/36674/
Subject: LU-10934 llite: integrate statx() API with Lustre
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 3f7853b31ef6f5a6c2837403910083057728a842

[Gerrit Updater]

Yingjin Qian ([e-mail]) uploaded a new patch: https://review.whamcloud.com/36674
Subject: LU-10934 llite: integrate statx() API with Lustre
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 3bb2844b25767676ab56946a00aff16f02a82db9

[Andreas Dilger]

The coreutils commit is at:
https://github.com/coreutils/coreutils/commit/a99ab266110795ed94a9cb4d2765ddad9c4310da

[Aurelien Degremont (Inactive)]

Nice Andreas!

Do you have a pointer for this change? Does this mean this is optimized and only statx() is used when possible?

 

[Andreas Dilger]

The support for stat(1) and ls(1) to use statx(3) to fetch only the required attributes has landed to the upstream GNU coreutils package.

[Andreas Dilger]

There is a very preliminary patch to add statx() support to ls at: https://github.com/jtlayton/coreutils/commits/statx

[Aurelien Degremont (Inactive)]

For Lustre the second call will likely just read data from cache. The performance impact should be low.

But this is not good news. Maybe we should push coreutils in the right direction.

 

Having a proper full statx implementation in Lustre is still useful. Robinhood can clearly benefit from it.

[Andreas Dilger]

I found that the stat command was patched to call statx() to fetch file creation time in coreutils 0.28, but unfortunately this is implemented by calling statx() again on the file, rather than calling statx() in the first place to fetch all of the required/available attributes. This means both stat() and statx() will be called on the file, increasing overhead rather than decreasing it . I didn't see other uses of statx() in the current coreutils.

[Aurelien Degremont (Inactive)]

• statx() is added to Linux (Linux 4.11+)
• glibc supports statx() (glibc 2.28+ -> RHEL 8, Ubuntu 18.10+)
• statx() takes benefit from LSOM (https://jira.whamcloud.com/browse/LU-10934)
• ls supports statx() (TBD)

As far as I've seen, ls guys are not really eager to support statx