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  1. Lustre
  2. LU-8025

ll_direct_io code introduced in LU-6260 is based on 2.4/2.5, ignores LU-1669

Details

    • Bug
    • Resolution: Fixed
    • Major
    • Lustre 2.9.0
    • Lustre 2.7.0, Lustre 2.8.0
    • None
    • 3
    • 9223372036854775807

    Description

      The patch for ll_direct_(io/IO_26) we got from Al Viro is based on the 2.4-2.5 code, and reverts several of the changes made by LU-1669 to the direct IO path. It seems we took his version without noting that important changes had been made in that function.

      The i_mutex, for example, no longer provides the expected protection.

      Thankfully for older kernels we left the updated code alone, but the code we call for 3.16 kernels is definitely wrong and needs to be updated to match current Lustre. It seems we need to take more care when forward/side-porting from the upstream kernels.

      Unfortunately, I won't be able to provide a patch for this. If correct direct IO behavior on 3.16 and newer kernels is important to someone, fixing it shouldn't be too hard - Just look at the code that follows:

      #else /* !HAVE_DIRECTIO_ITER && !HAVE_IOV_ITER_RW */
      

      in lustre/llite/rw26.c, and re-write the code above it to have the same approach to locking. Looking at the LU-6260 patch may help:
      http://review.whamcloud.com/#/c/14665/9

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            [LU-8025] ll_direct_io code introduced in LU-6260 is based on 2.4/2.5, ignores LU-1669
            pjones Peter Jones added a comment -

            Landed for 2.9

            pjones Peter Jones added a comment - Landed for 2.9

            Oleg Drokin (oleg.drokin@intel.com) merged in patch http://review.whamcloud.com/19840/
            Subject: LU-8025 llite: make vvp_io_write_start lockless for newer kernels
            Project: fs/lustre-release
            Branch: master
            Current Patch Set:
            Commit: f38911bc6a0e472e43b901bcb8ab74fc36c4e1e1

            gerrit Gerrit Updater added a comment - Oleg Drokin (oleg.drokin@intel.com) merged in patch http://review.whamcloud.com/19840/ Subject: LU-8025 llite: make vvp_io_write_start lockless for newer kernels Project: fs/lustre-release Branch: master Current Patch Set: Commit: f38911bc6a0e472e43b901bcb8ab74fc36c4e1e1

            dmesg output from the failed RHEL7 sanityn 77a run.

            simmonsja James A Simmons added a comment - dmesg output from the failed RHEL7 sanityn 77a run.

            James Simmons (uja.ornl@yahoo.com) uploaded a new patch: http://review.whamcloud.com/19840
            Subject: LU-8025 llite: make vvp_io_write_start lockless for newer kernels
            Project: fs/lustre-release
            Branch: master
            Current Patch Set: 1
            Commit: 1ac869430759817b29c2d6ac4b4939e369fc3e44

            gerrit Gerrit Updater added a comment - James Simmons (uja.ornl@yahoo.com) uploaded a new patch: http://review.whamcloud.com/19840 Subject: LU-8025 llite: make vvp_io_write_start lockless for newer kernels Project: fs/lustre-release Branch: master Current Patch Set: 1 Commit: 1ac869430759817b29c2d6ac4b4939e369fc3e44

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              wc-triage WC Triage
              paf Patrick Farrell (Inactive)
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                Updated:
                Resolved: