+++ This bug was initially created as a clone of Bug #1450975 +++

Description of problem:
On demand file migration is broken in upstream currently. This bug is created to track the fix for it.


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:

--- Additional comment from Worker Ant on 2017-05-15 18:31:50 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#2) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-16 13:16:10 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#3) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-17 14:05:34 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#4) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-18 12:00:16 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#5) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-22 08:08:54 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#6) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-23 12:31:42 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#7) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-23 13:59:50 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#8) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-24 08:47:47 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#9) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-29 12:33:25 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#10) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-29 12:36:38 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#11) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-29 18:01:07 MVT ---

REVIEW: https://review.gluster.org/17115 (cluster/dht: fix on demand migration files from client) posted (#12) for review on master by Susant Palai (spalai)

--- Additional comment from Worker Ant on 2017-05-30 05:43:03 MVT ---

COMMIT: https://review.gluster.org/17115 committed in master by Shyamsundar Ranganathan (srangana) 
------
commit 1b1f871ca41b08671ebb327dba464aeb6c82e776
Author: Susant Palai <spalai>
Date:   Tue Apr 25 18:32:45 2017 +0530

    cluster/dht: fix on demand migration files from client
    
        On demand migration of files i.e. migration done by clients
        triggered by a setfattr was broken.
    
        Dependency on defrag led to crash when migration was triggered from
        client.
    
        Note: This functionality is not available for tiered volumes. Migration
        from tier served client will fail with ENOTSUP.
    
        usage (But refer to the steps mentioned below to avoid any issues) :
        setfattr -n "trusted.distribute.migrate-data" -v "1" <filename>
    
        The purpose of fixing the on-demand client migration was to give a
        workaround where the user has lots of empty directories compared to
        files and want to do a remove-brick process.
    
        Here are the steps to trigger file migration for remove-brick process from
        client. (This is highly recommended to follow below steps as is)
    
        Let's say it is a replica volume and user want to remove a replica pair
        named brick1 and brick2. (Make sure healing is completed before you run
        these steps)
    
        Step-1: Start remove-brick process
         - gluster v remove-brick <volname> brick1 brick2 start
        Step-2: Kill the rebalance daemon
         - ps aux | grep glusterfs | grep rebalance\/ | awk '{print $2}' | xargs kill
        Step-3: Do a fresh mount as mentioned here
         -  glusterfs -s ${localhostname} --volfile-id rebalance/$volume-name /tmp/mount/point
        Step-4: Go to one of the bricks (among brick1 and brick2)
         - cd <brick1 path>
        Step-5: Run the following command.
         - find . -not \( -path ./.glusterfs -prune \) -type f -not -perm 01000 -exec bash -c 'setfattr -n "distribute.fix.layout" -v "1" ${mountpoint}/$(dirname '{}')' \; -exec  setfattr -n "trusted.distribute.migrate-data" -v "1" ${mountpoint}/'{}' \;
    
        This command will ignore the linkto files and empty directories. Do a fix-layout of
        the parent directory. And trigger a migration operation on the files.
    
        Step-6: Once this process is completed do "remove-brick force"
         - gluster v remove-brick <volname> brick1 brick2 force
    
        Note: Use the above script only when there are large number of empty directories.
        Since the script does a crawl on the brick side directly and avoids directories those
        are empty, the time spent on fixing layout on those directories are eliminated(even if the script
        does not do fix-layout on empty directories, post remove-brick a fresh layout will be built
        for the directory, hence not affecting application continuity).
    
        Detailing the expectation for hardlink migartion with this patch:
            Hardlink is migrated only for remove-brick process. It is highly essential
        to have a new mount(step-3) for the hardlink migration to happen. Why?:
        setfattr operation is an inode based operation. Since, we are doing setfattr from
        fuse mount here, inode_path will try to build path from the linked dentries to the inode.
        For a file without hardlinks the path construction will be correct. But for hardlinks,
        the inode will have multiple dentries linked.
    
                Without fresh mount, inode_path will always get the most recently linked dentry.
        e.g. if there are three hardlinks named dir1/link1, dir2/link2, dir3/link3, on a client
        where these hardlinks are looked up, inode_path will always return the path dir3/link3
        if dir3/link3 was looked up most recently. Hence, we won't be able to create linkto
        files for all other hardlinks on destination (read gf_defrag_handle_hardlink for more details
        on hardlink migration).
    
                With a fresh mount, the lookup and setfattr become serialized. e.g. link2 won't be
        looked up until link1 is looked up and migrated. Hence, inode_path will always have the correct
        path, in this case link1 dentry is picked up(as this is the most recently looked up inode) and
        the path is built right.
    
        Note: If you run the above script on an existing mount(all entries looked up), hard links may
        not be migrated, but there should not be any other issue. Please raise a bug, if you find any
        issue.
    
        Tests: Manual
    
    
    Change-Id: I9854cdd4955d9e24494f348fb29ba856ea7ac50a
    BUG: 1450975
    Signed-off-by: Susant Palai <spalai>
    Reviewed-on: https://review.gluster.org/17115
    NetBSD-regression: NetBSD Build System <jenkins.org>
    CentOS-regression: Gluster Build System <jenkins.org>
    Smoke: Gluster Build System <jenkins.org>
    Reviewed-by: Raghavendra G <rgowdapp>