[LU-13062] OST offset defaults to 0 when coying a PFL via xattrs

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Affects Version/s: Lustre 2.12.3
• Labels: easy
• Severity: 3
• Assignee: Mikhail Pershin
• Reporter: Clément Barthelemy (Inactive)

Description

 I have a small tool (attached) that duplicates Lustre files using raw xattrs (i.e standard mknod + setxattr).

With this method, PFL components that were initialized on the original file seem to always be created on OST index 0 on the duplicated file.

For example, let's say that we have 4 OSTs and we create a PFL file comp_file with 2 components and explicit OST offsets 2 and 3.

  $ lfs setstripe -E 1M -c 2 -i 2 -E -1 -c -1 -i 3 comp_file
  $ lfs getstripe comp_file
  comp_file
  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:   1048576
      lmm_stripe_count:  2
      lmm_stripe_size:   65536
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 2
      lmm_objects:
      - 0: { l_ost_idx: 2, l_fid: [0x100020000:0x7c:0x0] }
      - 1: { l_ost_idx: 3, l_fid: [0x100030000:0x53:0x0] }

    lcme_id:             2
    lcme_mirror_id:      0
    lcme_flags:          0
    lcme_extent.e_start: 1048576
    lcme_extent.e_end:   EOF
      lmm_stripe_count:  -1
      lmm_stripe_size:   65536
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 3

Calling the small tool to duplicate this layout into a new file comp_file_dup sets the first lmm_stripe_offset to 0.

$ ./simple_lustre_dup comp_file comp_file_dup
$ lfs getstripe comp_file_dup
 comp_file_dup
 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: 1048576
 lmm_stripe_count: 2
 lmm_stripe_size: 65536
 lmm_pattern: raid0
 lmm_layout_gen: 0
 lmm_stripe_offset: 0
 lmm_objects:
 - 0: { l_ost_idx: 0, l_fid: [0x100000000:0x357:0x0] }
 - 1: { l_ost_idx: 1, l_fid: [0x100010000:0x367:0x0] }
lcme_id: 2
 lcme_mirror_id: 0
 lcme_flags: 0
 lcme_extent.e_start: 1048576
 lcme_extent.e_end: EOF
 lmm_stripe_count: -1
 lmm_stripe_size: 65536
 lmm_pattern: raid0
 lmm_layout_gen: 0
 lmm_stripe_offset: 3

 

As was explained to me by Andreas, it makes sense to ignore the offset on duplication but -1 would be a better default value, letting the MDS choose the most appropriate OST.

According to Andreas this might be related to

LU-2809 llite: Do not return layout_gen for getxattr

LU-9484 llite: eat -EEXIST on setting trusted.lov

Issue Links

• is related to: LU-16500 "lfs migrate <file>" preserves specific layout too much