[Bugs] [Bug 1157985] New: [USS]: deletion and creation of snapshots with same name causes problems

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1157985

            Bug ID: 1157985
           Summary: [USS]: deletion and creation of snapshots with same
                    name causes problems
           Product: GlusterFS
           Version: 3.6.0
         Component: snapshot
          Assignee: bugs at gluster.org
          Reporter: rabhat at redhat.com
                CC: bugs at gluster.org, gluster-bugs at redhat.com
        Depends On: 1151004
            Blocks: 1157452



+++ This bug was initially created as a clone of Bug #1151004 +++

Description of problem:

The deletion and recreation of a snapshot with same name creates problems while
accessing the contents of newly created snapshot bu giving ENOTCONN errors.


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


How reproducible:
Always

Steps to Reproduce:
1. Create a file on the glusterfs mount point
2. Create a snapshot "snap1"
3. delete the file
4. delete the snapshot "snap1"
5. create a snapshot "snap1"
6. try to access snap1

Actual results:
applications get ENOTCONN

Expected results:
Applications should not get ENOTCONN

Additional info:
When the snapshot "snap1" is created first time and accessed (<mount
point>/<entry point>/snap1/<filename>), a new inode and dentry were created for
snap1 with parent being the entry point. Within the inode context the glfs_t
instance to access the snapshot and the handle to access the inode in the
snapshot world (or gfapi world in this case) is saved. But when the snapshot
was deleted and recreated, a new glfs_t instance is established (older one
being destroyed). So to access snap1 now, we have to do yet another lookup and
save the glfs_t instance and the new handle within the inode context. Since
that was not being done, older glfs_t instance was still used which gave
ENOTCONN when accessed as the corresponding snapshot volume does not exist
anymore.

--- Additional comment from Anand Avati on 2014-10-09 08:30:19 EDT ---

REVIEW: http://review.gluster.org/8917 (features/snapview-server: check if the
reference to the snapshot world is correct before doing any fop) posted (#1)
for review on master by Raghavendra Bhat (raghavendra at redhat.com)

--- Additional comment from Anand Avati on 2014-10-10 03:35:18 EDT ---

REVIEW: http://review.gluster.org/8917 (features/snapview-server: check if the
reference to the snapshot world is correct before doing any fop) posted (#2)
for review on master by Raghavendra Bhat (raghavendra at redhat.com)

--- Additional comment from Anand Avati on 2014-10-28 03:08:14 EDT ---

COMMIT: http://review.gluster.org/8917 committed in master by Vijay Bellur
(vbellur at redhat.com) 
------
commit 1fa3e87db77bb379173723a5e75b361a8e192f09
Author: Raghavendra Bhat <raghavendra at redhat.com>
Date:   Thu Oct 9 17:32:48 2014 +0530

    features/snapview-server: check if the reference to the snapshot world is
    correct before doing any fop

    The following operations might lead to problems:
    * Create a file on the glusterfs mount point
    * Create a snapshot (say "snap1")
    * Access the contents of the snapshot
    * Delete the file from the mount point
    * Delete the snapshot "snap1"
    * Create a new snapshot "snap1"

    Now accessing the new snapshot "snap1" gives problems. Because the inode
and
    dentry created for snap1 would not be deleted upon the deletion of the
snapshot
    (as deletion of snapshot is a gluster cli operation, not a fop). So next
time
    upon creation of a new snap with same name, the previous inode and dentry
itself
    will be used. But the inode context contains old information about the
glfs_t
    instance and the handle in the gfapi world. Directly accessing them without
    proper check leads to ENOTCONN errors. Thus the glfs_t instance should be
    checked before accessing. If its wrong, then right instance should be
obtained
    by doing the lookup.

    Change-Id: Idca0c8015ff632447cea206a4807d8ef968424fa
    BUG: 1151004
    Signed-off-by: Raghavendra Bhat <raghavendra at redhat.com>
    Reviewed-on: http://review.gluster.org/8917
    Tested-by: Gluster Build System <jenkins at build.gluster.com>
    Reviewed-by: Vijay Bellur <vbellur at redhat.com>


Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1151004
[Bug 1151004] [USS]: deletion and creation of snapshots with same name
causes problems
https://bugzilla.redhat.com/show_bug.cgi?id=1157452
[Bug 1157452] [USS]: deletion and creation of snapshots with same name
causes problems
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