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  1. Lustre
  2. LU-11916

LSOM: lazy_stat mount option not recognized

Details

    • Bug
    • Resolution: Won't Fix
    • Minor
    • None
    • Lustre 2.12.0
    • None
    • CentOS 7.6, MOFED 4.5
    • 3
    • 9223372036854775807

    Description

      I was trying to use "LSOM enforced" on a 2.12 client (for testing purpose, not very important), and noticed the lazy_stat option doesn't seem to work:

      [794713.969118] LustreError: 152-6: Unknown option 'lazy_stat', won't mount.

      This new mount option was mentioned in Li Xi's presentation at LUG'18 (page 7) http://cdn.opensfs.org/wp-content/uploads/2018/04/Xi-Lazy_Size_on_MDS_DDN.pdf

      Is there a way to enforce LSOM on a Lustre client, or not yet?
      Thanks!
      Stephane

      Attachments

        Issue Links

          is related to

          Improvement - An improvement or enhancement to an existing feature or task. LU-10934 integrate statx() API with Lustre

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Improvement - An improvement or enhancement to an existing feature or task. LU-11554 Make stat() work with LSOM

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Activity

            [LU-11916] LSOM: lazy_stat mount option not recognized
            sthiell Stephane Thiell added a comment -

            Excellent, thanks!

            sthiell Stephane Thiell added a comment - Excellent, thanks!
            adilger Andreas Dilger added a comment -

            The statx() API is going to land soon, and "lfs find" already can understand LSOM.

            adilger Andreas Dilger added a comment - The statx() API is going to land soon, and " lfs find " already can understand LSOM.
            sthiell Stephane Thiell added a comment -

            Thanks Andreas for the information and pointers, this is super helpful. I understand the interest of LSOM for MDT-level scanning, but I wanted to see how it would break (or not) applications if also enforced for (regular) stat(). So no real life use-case at the moment, but I'll think about it during the weekend.

            sthiell Stephane Thiell added a comment - Thanks Andreas for the information and pointers, this is super helpful. I understand the interest of LSOM for MDT-level scanning, but I wanted to see how it would break (or not) applications if also enforced for (regular) stat() . So no real life use-case at the moment, but I'll think about it during the weekend.
            adilger Andreas Dilger added a comment -

            The "lazy_stat" mount option is not in the 2.12 release. The closest is patch https://review.whamcloud.com/33412
            "LU-11554 som: Make stat() work with LSOM", but it also is not yet landed, since it isn't clear what the usage implications are.

            The current LSOM implementation isn't just "the size is a bit outdated", it is "the size and blocks stored on the MDS are zero until after the file is closed", so this would likely break many applications, and this can only be set on a per-mountpoint basis.

            Could you explain more how you want to us LSOM? The current implementation is mostly intended for MDT-level scanning. There is also a patch to add support for "lfs find" that is fairly safe, and discussion around adding support for statx(), which is what I think applications should use when they want the lazy size.

            For RBH usage, the 33412 patch and a separate mountpoint may be enough, as long as you don't trust the size on recently-created files.

            adilger Andreas Dilger added a comment - The " lazy_stat " mount option is not in the 2.12 release. The closest is patch https://review.whamcloud.com/33412 " LU-11554 som: Make stat() work with LSOM ", but it also is not yet landed, since it isn't clear what the usage implications are. The current LSOM implementation isn't just "the size is a bit outdated", it is "the size and blocks stored on the MDS are zero until after the file is closed", so this would likely break many applications, and this can only be set on a per-mountpoint basis. Could you explain more how you want to us LSOM? The current implementation is mostly intended for MDT-level scanning. There is also a patch to add support for " lfs find " that is fairly safe, and discussion around adding support for statx() , which is what I think applications should use when they want the lazy size. For RBH usage, the 33412 patch and a separate mountpoint may be enough, as long as you don't trust the size on recently-created files.
            pjones Peter Jones added a comment -

            Qian

            Can you comment as to whether this was included in the feature as it ended up in 2.12?

            Peter

            pjones Peter Jones added a comment - Qian Can you comment as to whether this was included in the feature as it ended up in 2.12? Peter

            People

              qian_wc Qian Yingjin
              sthiell Stephane Thiell
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                Updated:
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