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  r237929 | glebius | 2012-07-01 19:30:43 +0400 (вс, 01 июл 2012) | 6 lines

  In g_mirror_regular_request() upon successful delivery treat
  BIO_DELETE requests same way as BIO_WRITE removing them from
  queue. This fixes panic with BIO_DELETE operations on geom_mirror.

  Reviewed by:    pjd

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  r237930 | glebius | 2012-07-01 19:43:52 +0400 (вс, 01 июл 2012) | 20 lines

  Make geom_mirror more friendly to SSDs. To properly support TRIM,
  we need to pass BIO_DELETE requests down to providers that support
  it. Also, we need to announce our support for BIO_DELETE to upper
  consumer. This requires:

  - In g_mirror_start() return true for "GEOM::candelete" request.
  - In g_mirror_init_disk() probe below provider for "GEOM::candelete"
    attribute, and mark disk with a flag if it does support BIO_DELETE.
  - In g_mirror_register_request() distribute BIO_DELETE requests only
    to those disks, that do support it.

  Note that we announce "GEOM::candelete" as true unconditionally of
  whether we have TRIM-capable media down below or not. This is made
  intentionally, because upper consumer (usually UFS) requests the
  attribite only once at mount time. And if user ever migrates his
  mirror from HDDs to SSDs, then he/she would get TRIM working without
  remounting filesystem.

  Reviewed by:    pjd

Approved by:	re (kib)