[LU-16831] "lfs setstripe" should limit stripe count for component size

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0, Lustre 2.15.5
• Affects Version/s: Lustre 2.16.0
• Labels: easy
• Severity: 3
• Assignee: Zhenyu Xu
• Reporter: Andreas Dilger

Description

It appears that if "lfs setstripe" requests a stripe count that is larger than component_size / stripe_size then the requested number of OST objects will be created, but the ones at the end of the component will be inaccessible.

For example, creating a 1MiB component with 4x 1MiB stripes will create 3 OST objects that cannot be used:

# lfs setstripe -E 1M -c 4 -E eof -c 4 /mnt/testfs/badstripe
# lfs getstripe /mnt/testfs/badstripe
  lcm_entry_count:   2
    lcme_id:             1
    lcme_flags:          init
    lcme_extent.e_start: 0
    lcme_extent.e_end:   1048576
      lmm_stripe_count:  4
      lmm_stripe_size:   1048576
      lmm_stripe_offset: 1
      lmm_objects:
      - 0: { l_ost_idx: 1, l_fid: [0x340000403:0x163:0x0] }
      - 1: { l_ost_idx: 2, l_fid: [0x380000403:0x163:0x0] }
      - 2: { l_ost_idx: 3, l_fid: [0x3c0000403:0x1cd:0x0] }
      - 3: { l_ost_idx: 0, l_fid: [0x300000403:0x1a3:0x0] }

    lcme_id:             2
    lcme_flags:          0
    lcme_extent.e_start: 1048576
    lcme_extent.e_end:   EOF
      lmm_stripe_count:  4
      lmm_stripe_size:   1048576
      lmm_stripe_offset: -1

In this case, the MDS should limit the stripe count to:

        stripe_count = min(requested_stripe_count, (comp_end - comp_start) / stripe_size);

Issue Links

• is related to: LU-14554 Improve usability of "lfs mirror" commands