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  1. Lustre
  2. LU-4152

layout locks can cause deadlock

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Details

    • Bug
    • Status: Resolved
    • Blocker
    • Resolution: Fixed
    • Lustre 2.5.0, Lustre 2.6.0
    • Lustre 2.6.0, Lustre 2.5.1
    • le
    • 3
    • 11269

    Description

      LU-1876 adds mdt_object_open_lock() which acquires lock in 2 steps for layout locks.
      A deadlock is possible since it isn't atomic and ibits locks are reprocessed until first blocking lock found.

      Such situation was hit with mdt_reint_open() & mdt_intent_getattr()

      mdt_reint_open()->mdt_open_by_fid_lock() takes first part of the lock (ibits=5),
      mdt_intent_getattr() tries to obtain lock (ibits=17)
      mdt_open_by_fid_lock() tries to obtain second part but fails due to some conflict with another layout lock2. During cancellation of lock2 only getattr lock is reprocessed.
      http://review.whamcloud.com/#/c/7148/1 can help, but it is better to fix mdt_open_by_fid_lock()

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              green Oleg Drokin
              askulysh Andriy Skulysh
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                Created:
                Updated:
                Resolved: