[Bugs] [Bug 1394298] Add hole punch support

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1394298

Ram Ankireddypalle <areddy at commvault.com> changed:

           What    |Removed                     |Added
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              Flags|needinfo?(areddy at commvault. |
                   |com)                        |



--- Comment #2 from Ram Ankireddypalle <areddy at commvault.com> ---
(In reply to Ravishankar N from comment #1)
> Hi Ram, Need some clarification here. What I meant to say in the
> mailing-list thread was fallocate with keep-size flag (and therefore the
> hole-punch flag also) will report incorrect disk usage for the file:
> 
> 
> On a normal XFS file system:
> ==============================
> 0:root at vm4 ~$ #create a file.
> 0:root at vm4 ~$ echo > file
> 0:root at vm4 ~$ #fallocate 1G with keep size flag.
> 0:root at vm4 ~$ fallocate -o0 -l1G -n file
> 0:root at vm4 ~$ #check file size and disk space usage.
> 0:root at vm4 ~$ ll -h file
> -rw-r--r--. 1 root root 1 Nov 11 22:09 file
> 0:root at vm4 ~$ du -h file
> 1.0G    file
> 0:root at vm4 ~$
> 0:root at vm4 ~$ #punch 512MB hole and check usage again
> 0:root at vm4 ~$ fallocate -o0 -l512M -p file
> 0:root at vm4 ~$ ll -h file
> -rw-r--r--. 1 root root 1 Nov 11 22:10 file
> 0:root at vm4 ~$ du -h file
> 512M    file
> 0:root at vm4 ~$
> 
> 
> On a normal plain distribute 1 brick volume using fuse mount:
> ===============================================================
> 0:root at vm4 fuse_mnt$ echo >file
> 0:root at vm4 fuse_mnt$ fallocate -o0 -l1G -n file
> 0:root at vm4 fuse_mnt$ ll -h file
> -rw-r--r--. 1 root root 1 Nov 11 22:13 file
> 0:root at vm4 fuse_mnt$ du -h file
> 512     file -->This is wrong.
> 0:root at vm4 fuse_mnt$
> 0:root at vm4 fuse_mnt$ #run the command on the backend brick and observe
> correct disk usage is reported.
> 0:root at vm4 fuse_mnt$
> 0:root at vm4 fuse_mnt$ ll -h /bricks/brick1/file
> -rw-r--r--. 2 root root 1 Nov 11 22:13 /bricks/brick1/file
> 0:root at vm4 fuse_mnt$ du -h /bricks/brick1/file
> 1.0G    /bricks/brick1/file
> 0:root at vm4 fuse_mnt$
> 0:root at vm4 fuse_mnt$
> 0:root at vm4 fuse_mnt$ #punch hole
> 0:root at vm4 fuse_mnt$ fallocate -o0 -l^C
> 130:root at vm4 fuse_mnt$ fallocate -o0 -l512M -p file
> 0:root at vm4 fuse_mnt$ ll -h file
> -rw-r--r--. 1 root root 1 Nov 11 22:14 file
> 0:root at vm4 fuse_mnt$ du -h file
> 512     file
> 0:root at vm4 fuse_mnt$
> 0:root at vm4 fuse_mnt$ ll -h /bricks/brick1/file
> -rw-r--r--. 2 root root 1 Nov 11 22:14 /bricks/brick1/file
> 0:root at vm4 fuse_mnt$ du -h /bricks/brick1/file
> 512M    /bricks/brick1/file
> 0:root at vm4 fuse_mnt$
> ========================================
> 
> But you seem to be saying punch hole *fails* on the file. Not sure if we are
> on the same page here. Does this happen only on disperse volumes? Can you
> explain the steps in detail?

Ravi,
      Thanks for checking this. For the disperse volumes fallocate fails. In
3.7.8 hole punching support was not available for disperse volumes. During
glusterfs developer summit Praneeth K mentioned that support for adding hole
punching to disperse volumes is in works. 

[root at flash1 glusterfs]# gluster volume info

Volume Name: FlashStoragePool
Type: Distributed-Disperse
Volume ID: 1c49c595-5117-481d-8abe-83a4c6579c91
Status: Started
Number of Bricks: 2 x (2 + 1) = 6
Transport-type: tcp
Bricks:
Brick1: flash1sds:/ws/disk1/ws_brick
Brick2: flash2sds:/ws/disk1/ws_brick
Brick3: flash3sds:/ws/disk1/ws_brick
Brick4: flash1sds:/ws/disk2/ws_brick
Brick5: flash2sds:/ws/disk2/ws_brick
Brick6: flash3sds:/ws/disk2/ws_brick
Options Reconfigured:
performance.readdir-ahead: on
nfs.export-dirs: off
nfs.export-volumes: off
nfs.disable: on
performance.read-ahead: off
auth.allow: flash1sds,flash2sds,flash3sds

[root at flash1 glusterfs]# mount
...
flash1sds:/FlashStoragePool on /ws/glus type fuse.glusterfs
(rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,max_read=131072)
...

[root at flash1 glus]# fallocate -o0 -l1G -n test
fallocate: keep size mode (-n option) unsupported

[root at flash1 glus]# fallocate -o0 -l1G  test
fallocate: test: fallocate failed: Operation not supported

ws-glus.log
[2016-11-11 17:02:32.281455] W [fuse-bridge.c:1282:fuse_err_cbk]
0-glusterfs-fuse: 18948: FALLOCATE() ERR => -1 (Operation not supported)
[2016-11-11 17:03:38.036083] W [fuse-bridge.c:1282:fuse_err_cbk]
0-glusterfs-fuse: 18958: FALLOCATE() ERR => -1 (Operation not supported)
[2016-11-11 17:04:10.588579] W [fuse-bridge.c:1282:fuse_err_cbk]
0-glusterfs-fuse: 18964: FALLOCATE() ERR => -1 (Operation not supported)

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