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  1. Lustre
  2. LU-12586

truncate to start of uninstantiated PFL component silently fails

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: Lustre 2.13.0, Lustre 2.12.2, Lustre 2.10.8
    • Fix Version/s: Lustre 2.14.0
    • Labels:
      None
    • Severity:
      3
    • Rank (Obsolete):
      9223372036854775807

      Description

      Truncate to exactly the first byte of an uninstantiated PFL component doesn't work - It has no effect.

      Example:

      [root@cent7c02 lustre]# mkdir testdir; lfs setstripe -E 4M --stripe-count=1 -E -1 testdir
      [root@cent7c02 lustre]# touch testdir/testfile; lfs getstripe testdir/testfile
      testdir/testfile
        lcm_layout_gen:    2
        lcm_mirror_count:  1
        lcm_entry_count:   2
          lcme_id:             1
          lcme_mirror_id:      0
          lcme_flags:          init
          lcme_extent.e_start: 0
          lcme_extent.e_end:   4194304
            lmm_stripe_count:  1
            lmm_stripe_size:   1048576
            lmm_pattern:       raid0
            lmm_layout_gen:    0
            lmm_stripe_offset: 0
            lmm_objects:
            - 0: { l_ost_idx: 0, l_fid: [0x100000000:0x24b:0x0] }    lcme_id:             2
          lcme_mirror_id:      0
          lcme_flags:          0
          lcme_extent.e_start: 4194304
          lcme_extent.e_end:   EOF
            lmm_stripe_count:  1
            lmm_stripe_size:   1048576
            lmm_pattern:       raid0
            lmm_layout_gen:    0
            lmm_stripe_offset: -1[root@cent7c02 lustre]# truncate --size 4194304 testdir/testfile; ls -la testdir/testfile
      -rw-r--r-- 1 root root 0 Jul 24 15:11 testdir/testfile
      [root@cent7c02 lustre]# truncate --size 4194303 testdir/testfile; ls -la testdir/testfile
      -rw-r--r-- 1 root root 4194303 Jul 24 15:11 testdir/testfile
      [root@cent7c02 lustre]# truncate --size 4194305 testdir/testfile; ls -la testdir/testfile
      -rw-r--r-- 1 root root 4194305 Jul 24 15:11 testdir/testfile 

      Notice that the truncate to 4 MiB (4194304) leaves the size at 0, but truncate to 4194303 or 4194305 works fine.

      Once the component is instantiated, this works fine:

      [root@cent7c02 lustre]# truncate --size 4194305 testdir/testfile; ls -la testdir/testfile
      -rw-r--r-- 1 root root 4194305 Jul 24 15:14 testdir/testfile
      [root@cent7c02 lustre]# lfs getstripe testdir/testfile
      testdir/testfile
        lcm_layout_gen:    3
        lcm_mirror_count:  1
        lcm_entry_count:   2
          lcme_id:             1
          lcme_mirror_id:      0
          lcme_flags:          init
          lcme_extent.e_start: 0
          lcme_extent.e_end:   4194304
            lmm_stripe_count:  1
            lmm_stripe_size:   1048576
            lmm_pattern:       raid0
            lmm_layout_gen:    0
            lmm_stripe_offset: 1
            lmm_objects:
            - 0: { l_ost_idx: 1, l_fid: [0x100010000:0x24d:0x0] }    lcme_id:             2
          lcme_mirror_id:      0
          lcme_flags:          init
          lcme_extent.e_start: 4194304
          lcme_extent.e_end:   EOF
            lmm_stripe_count:  1
            lmm_stripe_size:   1048576
            lmm_pattern:       raid0
            lmm_layout_gen:    0
            lmm_stripe_offset: 0
            lmm_objects:
            - 0: { l_ost_idx: 0, l_fid: [0x100000000:0x24e:0x0] }
      [root@cent7c02 lustre]# truncate --size 4194304 testdir/testfile; ls -la testdir/testfile
      -rw-r--r-- 1 root root 4194304 Jul 24 15:14 testdir/testfile 

      This is due to a slightly mixup in the write intent code between "end" for truncate, which is a size, and "end" for a normal write, which is actually "endpos", ie, the position of the write cursor after a write, which is not actually accessed and so does not need to be instantiated.  But "end" for truncate is not endpos, it's end, ie, it's included.

      Fix coming momentarily.

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            • Assignee:
              bobijam Zhenyu Xu
              Reporter:
              pfarrell Patrick Farrell (Inactive)
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              Dates

              • Created:
                Updated:
                Resolved: