[LU-11486] FLR allows overlapping "write preferred" segments

• Type: Bug
• Resolution: Not a Bug
• Priority: Major
• Severity: 3
• Assignee: WC Triage
• Reporter: Patrick Farrell

Description

Close examination of sanity-flr test 0h shows something troubling.

Simply run the test to completion, but add an error statement so the file is retained.  Here's what the getstripe output on the file looks like after 0h (again, with no modification):

[root@cent7c01 lustre]# lfs getstripe f0h.sanity-flr 
f0h.sanity-flr
 lcm_layout_gen: 9
 lcm_mirror_count: 3
 lcm_entry_count: 4
 lcme_id: 65537
 lcme_mirror_id: 1
 lcme_flags: init
 lcme_extent.e_start: 0
 lcme_extent.e_end: 1048576
 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: [0x100000000:0x10:0x0] }
lcme_id: 65538
 lcme_mirror_id: 1
 lcme_flags: init,prefer
 lcme_extent.e_start: 1048576
 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: [0x100000000:0x11:0x0] }
lcme_id: 131075
 lcme_mirror_id: 2
 lcme_flags: init,prefer
 lcme_extent.e_start: 0
 lcme_extent.e_end: EOF
 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: [0x100010000:0x10:0x0] }
lcme_id: 196612
 lcme_mirror_id: 3
 lcme_flags: init
 lcme_extent.e_start: 0
 lcme_extent.e_end: EOF
 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: [0x100010000:0x11:0x0] } 

The key part is these two components, the second and third in the list above:

    lcme_id:             65538
    lcme_mirror_id:      1
    lcme_flags:          init,prefer
    lcme_extent.e_start: 1048576
    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: [0x100000000:0x11:0x0] }    lcme_id:             131075
    lcme_mirror_id:      2
    lcme_flags:          init,prefer
    lcme_extent.e_start: 0
    lcme_extent.e_end:   EOF
      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: [0x100010000:0x10:0x0] } 

 

The first component is in mirror 1, and runs from 1 MiB to EOF, and is preferred for write.  The second component is in mirror 2 and runs from 0 to EOF...  and is preferred for write.

This seems to be inherently conflicted.  I would think the tools should prevent setting overlapping "prefer" flags...?

Issue Links

• is related to: LU-11485 MDS allows "lfs setstripe" to mark last mirror as stale