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  1. Lustre
  2. LU-10810

SEEK_HOLE and SEEK_DATA support for lseek

Details

    • Improvement
    • Resolution: Fixed
    • Minor
    • Lustre 2.14.0
    • None
    • 9223372036854775807

    Description

      lseek with SEEK_HOLE and SEEK_DATA are really helpful  and easy to use tools for any usersapce applications like copy and backup. Currently lustre has min support implementation as per the man page which is not that useful however lustre does support fiemap ioctl which can be used for mapping data in the file.
      As we already have support for fiemap I guess with some implementation lustre can support SEEK_HOLE and SEEK_DATA flags. I guess having this support will be helpful to deal with sparse files. Any feedback about the implementation will be really helpful.

      Attachments

        Issue Links

          duplicates

          Bug - A problem which impairs or prevents the functions of the product. LU-13397 lfs migrate/mirror extend/resync does not preserve sparse file

          • Major - Major loss of function.
          • Resolved
          is related to

          Bug - A problem which impairs or prevents the functions of the product. LU-14143 SEEK_HOLE returns -ENXIO if file ends at components boundary

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Improvement - An improvement or enhancement to an existing feature or task. LU-11621 Add copy_file_range() API and use it for lfs migrate and mirror resync

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Improvement - An improvement or enhancement to an existing feature or task. LU-14217 better SEEK_HOLE/DATA support in OSD-ZFS

          • Major - Major loss of function.
          • Resolved
          is related to

          Bug - A problem which impairs or prevents the functions of the product. LU-1941 ZFS FIEMAP support

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          New Feature - A new feature of the product, which has yet to be developed. LU-3606 Implement fallocate() support for ldiskfs Lustre

          • Major - Major loss of function.
          • Resolved

          Improvement - An improvement or enhancement to an existing feature or task. LU-13155 "lfs migrate" and "lfs mirror" should fallocate() the target file

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Activity

            [LU-10810] SEEK_HOLE and SEEK_DATA support for lseek
            gerrit Gerrit Updater added a comment -

            "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50328
            Subject: LU-10810 test: test lseek support in tools
            Project: fs/lustre-release
            Branch: b2_12
            Current Patch Set: 1
            Commit: 59154a1c86e186c98359b042f96df389f0b91ebe

            gerrit Gerrit Updater added a comment - "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50328 Subject: LU-10810 test: test lseek support in tools Project: fs/lustre-release Branch: b2_12 Current Patch Set: 1 Commit: 59154a1c86e186c98359b042f96df389f0b91ebe
            gerrit Gerrit Updater added a comment -

            "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50327
            Subject: LU-10810 clio: SEEK_HOLE/SEEK_DATA on client side
            Project: fs/lustre-release
            Branch: b2_12
            Current Patch Set: 1
            Commit: a196f0c1aaac7d1e58aa85847256bc5f2e24f1c1

            gerrit Gerrit Updater added a comment - "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50327 Subject: LU-10810 clio: SEEK_HOLE/SEEK_DATA on client side Project: fs/lustre-release Branch: b2_12 Current Patch Set: 1 Commit: a196f0c1aaac7d1e58aa85847256bc5f2e24f1c1
            gerrit Gerrit Updater added a comment -

            "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50326
            Subject: LU-10810 ptlrpc: introduce OST_SEEK RPC
            Project: fs/lustre-release
            Branch: b2_12
            Current Patch Set: 1
            Commit: ff27b1c2da37c1d910da48738e97f7193f4453ef

            gerrit Gerrit Updater added a comment - "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50326 Subject: LU-10810 ptlrpc: introduce OST_SEEK RPC Project: fs/lustre-release Branch: b2_12 Current Patch Set: 1 Commit: ff27b1c2da37c1d910da48738e97f7193f4453ef
            gerrit Gerrit Updater added a comment -

            "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50325
            Subject: LU-10810 osd: implement lseek method in OSD
            Project: fs/lustre-release
            Branch: b2_12
            Current Patch Set: 1
            Commit: b21bc7e262aff42aa3fd90966a791de4ad515dd0

            gerrit Gerrit Updater added a comment - "Etienne AUJAMES <eaujames@ddn.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50325 Subject: LU-10810 osd: implement lseek method in OSD Project: fs/lustre-release Branch: b2_12 Current Patch Set: 1 Commit: b21bc7e262aff42aa3fd90966a791de4ad515dd0
            tappro Mikhail Pershin added a comment -

            Andreas, I've check these reports and in fact only couple of them are ldiskfs, in these cases there were old servers used, with just no lseek support. All ZFS tests are expected to be skipped. 

            In fact, I was testing recently ZFS 8.5 with exported dmu_offset_mext() to check how it behave and have found that there are problems.
            ZFS SEEK_HOLE/DATA support is unreliable because it doesn't work if there are dirty data, that cause all test to fail because we don't do full data sync prior each lseek. I was trying to sync data in tests but with no big success. Moreover I don't think test failures are problems, after all we could sync everything just to make test pass but that would not mean ZFS lseek is reliable until ZFS itself will handle dirty data.

            For now it can report HOLE at offset 1000 (correct) and immediately SEEK_DATA(1000) returns also 1000 (incorrectly) just because there are dirty data and it switches to generic approach (all file is data with hole at the end). I am afraid we cannot rely on ZFS until its option zfs_dmu_offset_next_sync is set, which in turn would cause zfs slowdown when SEEK_DATA is performed on it

            So basically ZFS server should report LSEEK support only if zfs_dmu_offset_next_sync is set AND dmu_offset_next is exported. And that should be done now I think, before we will start using ZFS 8.5 and find out that lseek is reported as supported but doesn't work as expected

            tappro Mikhail Pershin added a comment - Andreas, I've check these reports and in fact only couple of them are ldiskfs, in these cases there were old servers used, with just no lseek support. All ZFS tests are expected to be skipped.  In fact, I was testing recently ZFS 8.5 with exported dmu_offset_mext() to check how it behave and have found that there are problems. ZFS SEEK_HOLE/DATA support is unreliable because it doesn't work if there are dirty data, that cause all test to fail because we don't do full data sync prior each lseek. I was trying to sync data in tests but with no big success. Moreover I don't think test failures are problems, after all we could sync everything just to make test pass but that would not mean ZFS lseek is reliable until ZFS itself will handle dirty data. For now it can report HOLE at offset 1000 (correct) and immediately SEEK_DATA(1000) returns also 1000 (incorrectly) just because there are dirty data and it switches to generic approach (all file is data with hole at the end). I am afraid we cannot rely on ZFS until its option zfs_dmu_offset_next_sync is set, which in turn would cause zfs slowdown when SEEK_DATA is performed on it So basically ZFS server should report LSEEK support only if  zfs_dmu_offset_next_sync is set AND dmu_offset_next is exported. And that should be done now I think, before we will start using ZFS 8.5 and find out that lseek is reported as supported but doesn't work as expected
            adilger Andreas Dilger added a comment -

            Mike, I noticed some test runs are reporting no SEEK_HOLE support for test_430a,430b,430c, even though client and server are running on the current tip of master (v2_13_56-149-ge5c8f6670f):
            https://testing.whamcloud.com/search?horizon=518400&status%5B%5D=SKIP&test_set_script_id=f9516376-32bc-11e0-aaee-52540025f9ae&sub_test_script_id=4154d1b3-ab47-47e4-9ecd-ea85afa35353&source=sub_tests#redirect

            It doesn't look like all test runs are being skipped, but I didn't think this feature is specific to ZFS or ldiskfs, so I'm not sure why the subtests are being skipped.

            adilger Andreas Dilger added a comment - Mike, I noticed some test runs are reporting no SEEK_HOLE support for test_430a,430b,430c, even though client and server are running on the current tip of master (v2_13_56-149-ge5c8f6670f): https://testing.whamcloud.com/search?horizon=518400&status%5B%5D=SKIP&test_set_script_id=f9516376-32bc-11e0-aaee-52540025f9ae&sub_test_script_id=4154d1b3-ab47-47e4-9ecd-ea85afa35353&source=sub_tests#redirect It doesn't look like all test runs are being skipped, but I didn't think this feature is specific to ZFS or ldiskfs, so I'm not sure why the subtests are being skipped.
            pjones Peter Jones added a comment -

            Landed for 2.14

            pjones Peter Jones added a comment - Landed for 2.14
            gerrit Gerrit Updater added a comment -

            Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/40502/
            Subject: LU-10810 test: test lseek support in tools
            Project: fs/lustre-release
            Branch: master
            Current Patch Set:
            Commit: d633172a38519aba2585c2a1fdcdd821cb19010c

            gerrit Gerrit Updater added a comment - Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/40502/ Subject: LU-10810 test: test lseek support in tools Project: fs/lustre-release Branch: master Current Patch Set: Commit: d633172a38519aba2585c2a1fdcdd821cb19010c
            gerrit Gerrit Updater added a comment -

            Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/39708/
            Subject: LU-10810 clio: SEEK_HOLE/SEEK_DATA on client side
            Project: fs/lustre-release
            Branch: master
            Current Patch Set:
            Commit: cda353e6efae5013a26aedbe49d8aa6fb8fe456e

            gerrit Gerrit Updater added a comment - Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/39708/ Subject: LU-10810 clio: SEEK_HOLE/SEEK_DATA on client side Project: fs/lustre-release Branch: master Current Patch Set: Commit: cda353e6efae5013a26aedbe49d8aa6fb8fe456e
            gerrit Gerrit Updater added a comment -

            Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/39707/
            Subject: LU-10810 ptlrpc: introduce OST_SEEK RPC
            Project: fs/lustre-release
            Branch: master
            Current Patch Set:
            Commit: 6d5fe29066af5f8e40055fd89b285853c363e947

            gerrit Gerrit Updater added a comment - Oleg Drokin (green@whamcloud.com) merged in patch https://review.whamcloud.com/39707/ Subject: LU-10810 ptlrpc: introduce OST_SEEK RPC Project: fs/lustre-release Branch: master Current Patch Set: Commit: 6d5fe29066af5f8e40055fd89b285853c363e947

            People

              tappro Mikhail Pershin
              ljaliminche Lokesh N J (Inactive)
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              Dates

                Created:
                Updated:
                Resolved: