glusterfs.git/xlators/cluster/afr/src/afr.c, branch v3.5.0

glusterfs: zerofill support

2013-11-11T05:25:49+00:00

Add support for a new ZEROFILL fop. Zerofill writes zeroes to a file in
the specified range. This fop will be useful when a whole file needs to
be initialized with zero (could be useful for zero filled VM disk image
provisioning or  during scrubbing of VM disk images).

Client/application can issue this FOP for zeroing out. Gluster server
will zero out required range of bytes ie server offloaded zeroing. In
the absence of this fop,  client/application has to repetitively issue
write (zero) fop to the server, which is very inefficient method because
of the overheads involved in RPC calls  and acknowledgements.

WRITESAME is a  SCSI T10 command that takes a block of data as input and
writes the same data to other blocks and this write is handled
completely within the storage and hence is known as offload . Linux ,now
has support for SCSI WRITESAME command which is exposed to the user in
the form of BLKZEROOUT ioctl.  BD Xlator can exploit BLKZEROOUT ioctl to
implement this fop. Thus zeroing out operations can be completely
offloaded to the storage device , making it highly efficient.

The fop takes two arguments offset and size. It zeroes out 'size' number
of bytes in an opened file starting from 'offset' position.

This patch adds zerofill support to the following areas:
	- libglusterfs
	- io-stats
	- performance/md-cache,open-behind
	- quota
	- cluster/afr,dht,stripe
	- rpc/xdr
	- protocol/client,server
	- io-threads
	- marker
	- storage/posix
	- libgfapi

Client applications can exloit this fop by using glfs_zerofill introduced in
libgfapi.FUSE support to this fop has not been added as there is no system call
for this fop.

Changes from previous version 3:
* Removed redundant memory failure log messages

Changes from previous version 2:
* Rebased and fixed build error

Changes from previous version 1:
* Rebased for latest master

TODO :
     * Add zerofill support to trace xlator
     * Expose zerofill capability as part of gluster volume info

Here is a performance comparison of server offloaded zeofill vs zeroing
out using repeated writes.

[root@llmvm02 remote]# time ./offloaded aakash-test log 20

real	3m34.155s
user	0m0.018s
sys	0m0.040s
[root@llmvm02 remote]# time ./manually aakash-test log 20

real	4m23.043s
user	0m2.197s
sys	0m14.457s
[root@llmvm02 remote]# time ./offloaded aakash-test log 25;

real	4m28.363s
user	0m0.021s
sys	0m0.025s
[root@llmvm02 remote]# time ./manually aakash-test log 25

real	5m34.278s
user	0m2.957s
sys	0m18.808s

The argument log is a file which we want to set for logging purpose and
the third argument is size in GB .

As we can see there is a performance improvement of around 20% with this
fop.

Change-Id: I081159f5f7edde0ddb78169fb4c21c776ec91a18
BUG: 1028673
Signed-off-by: Aakash Lal Das 
Signed-off-by: M. Mohan Kumar 
Reviewed-on: http://review.gluster.org/5327
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

cluster/afr : Implementation of command "gluster volume heal vn statistics"

2013-10-14T21:41:44+00:00

"gluster volume heal volumename statistics" command gives the summary
of the afr crawl done based on the entries present in the xattrop
directory. Whenever afr crawls are attempted, the beginning time of
crawl, end time of crawl, no of files healed, heal-failed count and
number of files in split brain are shown along with the type of the
crawl. If crawl is already in progress then it will give the number
of files healed, heal failed count and number of files in split-brain
from the beginning of the crawl and instead of telling the end time of
the crawl, "CRAWL IN PROGRESS" message will be shown.

Output format:
command: "gluster volume heal volume-name statistics"
Output:
Gathering afr crawl statistics crawl statistics on volume volume-name
has been successful
------------------------------------------------

Crawl statistics for brick no 0
Hostname of brick 192.168.122.248

Starting time of crawl: Wed Jul 10 15:52:38 2013

Ending time of crawl: Wed Jul 10 15:52:38 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

Starting time of crawl: Wed Jul 10 15:52:38 2013

Ending time of crawl: Wed Jul 10 15:52:38 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

------------------------------------------------

Crawl statistics for brick no 1
Hostname of brick 192.168.122.1

Starting time of crawl: Wed Jul 10 15:52:42 2013

Ending time of crawl: Wed Jul 10 15:52:42 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

Starting time of crawl: Wed Jul 10 15:52:42 2013

Ending time of crawl: Wed Jul 10 15:52:42 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

--------------------------------------------------

Change-Id: I10bf9d10b005741db9973fb1352e0dd59ed99aa9
BUG: 949400
Signed-off-by: Venkatesh Somyajulu 
Reviewed-on: http://review.gluster.org/4790
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: Change Self-heal domain separator to ':'

2013-10-04T04:28:15+00:00

'-' can be present in a volume. This may lead to domain
collisions in future.

Tests:
Checked in gdb that domain comes with ':' separator:

Breakpoint 1, pl_common_inodelk (frame=0x7fdabcce51a4,
this=0x8bde20, volume=0x8b50d0 "r2-replicate-0:self-heal",
inode=0x7fdab822f0e8, cmd=6, flock=0x7fdabc76eee4,
loc=0x7fdabc76ede4, fd=0x0, xdata=0x7fdabc6e0ab0) at inodelk.c:597

Change-Id: I4456ae35ac8bf21e6361c34e9ad437f744a2e84b
BUG: 993981
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/6025
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: Let two data-self-heals compete in new domain

2013-07-04T04:35:30+00:00

Problem:
At the moment data-self-heal acquires locks in following
pattern. It takes full file lock then gets xattrs on files on both
replicas. Decides sources/sinks based on the xattrs. Now it acquires
lock from 0-128k then unlocks the full file lock. Syncs 0-128k range
from source to sink now acquires lock 128k+1 till 256k then unlocks
0-128k, syncs 128k+1 till 256k block... so on finally it takes full file
lock again then unlocks the final small range block.
It decrements pending counts and then unlocks the full file lock.

     This pattern of locks is chosen to avoid more than 1 self-heal
to be in progress. BUT if another self-heal tries to take a full
file lock while a self-heal is already in progress it will be put in
blocked queue, further inodelks from writes by the application will
also be put in blocked queue because of the way locks xlator grants
inodelks. So until the self-heal is complete writes are blocked.

Here is the code:
xlators/features/locks/src/inodelk.c - line 225
if (__blocked_lock_conflict (dom, lock) && !(__owner_has_lock (dom, lock))) {
         ret = -EAGAIN;
         if (can_block == 0)
                 goto out;

         gettimeofday (&lock->blkd_time, NULL);
         list_add_tail (&lock->blocked_locks, &dom->blocked_inodelks);
}

This leads to hangs in applications.

Fix:
Since we want to prevent two parallel self-heals. We let them compete
in a separate "domain". Lets call the domain on which the locks have
been taken on in previous approach as "data-domain".

In the new approach When a self-heal is triggered,
it acquires a full lock in the new domain "self-heal-domain".
    After this it performs data-self-heal using the locks in
    "data-domain" as before.
unlock the full file lock in "self-heal-domain"

With this approach, application's writevs don't have to wait
in pending queue when more than 1 self-heal is triggered.

Change-Id: Id79aef3dfa888945977fb9758374ac41c320d0d5
BUG: 967717
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/5100
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

cluster/afr: Refactor inodelk to handle multiple domains

2013-07-04T04:28:11+00:00

- afr_local_copy should not be memduping locked nodes, that would
  mean that lock is taken in self-heal on those nodes even before
  it actually takes the lock. So removed memdup code. Even entry
  lock related copying (lockee info) is also not necessary for
  self-heal functionality, so removing that as well. Since it is
  not local_copy anymore changed its name.

- My editor changed tabs to spaces.

Change-Id: I8dfb92cb8338e9a967c06907a8e29a8404782d61
BUG: 967717
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/5099
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

cluster/afr: Provide an option to disable afr durability

2013-07-03T14:33:13+00:00

Change-Id: I40eec20ca6b3f857245a2438883822e251077ee9
BUG: 979365
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/5269
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

glusterfs: discard (hole punch) support

2013-06-13T21:37:43+00:00

Add support for the DISCARD file operation. Discard punches a hole
in a file in the provided range. Block de-allocation is implemented
via fallocate() (as requested via fuse and passed on to the brick
fs) but a separate fop is created within gluster to emphasize the
fact that discard changes file data (the discarded region is
replaced with zeroes) and must invalidate caches where appropriate.

BUG: 963678
Change-Id: I34633a0bfff2187afeab4292a15f3cc9adf261af
Signed-off-by: Brian Foster 
Reviewed-on: http://review.gluster.org/5090
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

gluster: add fallocate fop support

2013-06-13T21:37:21+00:00

Implement support for the fallocate file operation. fallocate
allocates blocks for a particular inode such that future writes
to the associated region of the file are guaranteed not to fail
with ENOSPC.

This patch adds fallocate support to the following areas:

	- libglusterfs
	- mount/fuse
	- io-stats
	- performance/md-cache,open-behind
	- quota
	- cluster/afr,dht,stripe
	- rpc/xdr
	- protocol/client,server
	- io-threads
	- marker
	- storage/posix
	- libgfapi

BUG: 949242
Change-Id: Ice8e61351f9d6115c5df68768bc844abbf0ce8bd
Signed-off-by: Brian Foster 
Reviewed-on: http://review.gluster.org/4969
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: Empty string should not be default option val

2012-12-05T23:35:47+00:00

Glusterd does not allow empty string as default value. Changed
afr option values to disallow empty string as value.

Change-Id: I92a2d658907dbc6101e1139dd91f548acb5506f5
BUG: 859927
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/4271
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: Provide option to disable readdir failover

2012-12-03T08:11:02+00:00

In a replica pair unlike files, directories may not have their
content in same order, so readdir for same (offset, size) may
not give same entries on both the sobvolumes of replica pair.
Switching over from one subvolume to another may not be a good
idea sometimes. It may lead to duplicate entries or fewer entries
or both. This patch provides a way to disable readdir-failover
so that applications like rebalance can retry if they want to.

Change-Id: I2b23eb224a2e84016a561362932613ac824c11a0
BUG: 859387
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/4159
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur