<feed xmlns='http://www.w3.org/2005/Atom'>
<title>glusterfs.git/rpc/rpc-lib/src/rpc-transport.c, branch v5.0alpha</title>
<subtitle></subtitle>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/'/>
<entry>
<title>Land part 2 of clang-format changes</title>
<updated>2018-09-12T12:22:45+00:00</updated>
<author>
<name>Gluster Ant</name>
<email>bugzilla-bot@gluster.org</email>
</author>
<published>2018-09-12T12:22:45+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=e16868dede6455cab644805af6fe1ac312775e13'/>
<id>e16868dede6455cab644805af6fe1ac312775e13</id>
<content type='text'>
Change-Id: Ia84cc24c8924e6d22d02ac15f611c10e26db99b4
Signed-off-by: Nigel Babu &lt;nigelb@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Change-Id: Ia84cc24c8924e6d22d02ac15f611c10e26db99b4
Signed-off-by: Nigel Babu &lt;nigelb@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rpc: fix return value in rpc destroy</title>
<updated>2018-07-28T07:21:12+00:00</updated>
<author>
<name>Zhang Huan</name>
<email>zhanghuan@open-fs.com</email>
</author>
<published>2018-07-27T00:42:00+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=2e0744570fe1f6148e0c7b1c1a5bf98cc4eaf990'/>
<id>2e0744570fe1f6148e0c7b1c1a5bf98cc4eaf990</id>
<content type='text'>
Change-Id: I73a113e2d40f508fd53b273a990a2371692c87bf
fixes: bz#1607689
Signed-off-by: Zhang Huan &lt;zhanghuan@open-fs.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Change-Id: I73a113e2d40f508fd53b273a990a2371692c87bf
fixes: bz#1607689
Signed-off-by: Zhang Huan &lt;zhanghuan@open-fs.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rpc: add missing free of rpc-&gt;dnscache</title>
<updated>2018-07-28T07:21:12+00:00</updated>
<author>
<name>Zhang Huan</name>
<email>zhanghuan@open-fs.com</email>
</author>
<published>2018-07-23T08:07:59+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=e7c87f757c9dbf2492c22f8b5a4c9700e126af31'/>
<id>e7c87f757c9dbf2492c22f8b5a4c9700e126af31</id>
<content type='text'>
Change-Id: I3fa97b99bf23459cf548205d75d2cc7936b2310e
fixes: bz#1607689
Signed-off-by: Zhang Huan &lt;zhanghuan@open-fs.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Change-Id: I3fa97b99bf23459cf548205d75d2cc7936b2310e
fixes: bz#1607689
Signed-off-by: Zhang Huan &lt;zhanghuan@open-fs.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>All: run codespell on the code and fix issues.</title>
<updated>2018-07-22T14:40:16+00:00</updated>
<author>
<name>Yaniv Kaul</name>
<email>ykaul@redhat.com</email>
</author>
<published>2018-07-16T14:03:17+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=621138ce763eda8270d0a4f6d7209fd50ada8787'/>
<id>621138ce763eda8270d0a4f6d7209fd50ada8787</id>
<content type='text'>
Please review, it's not always just the comments that were fixed.
I've had to revert of course all calls to creat() that were changed
to create() ...

Only compile-tested!

Change-Id: I7d02e82d9766e272a7fd9cc68e51901d69e5aab5
updates: bz#1193929
Signed-off-by: Yaniv Kaul &lt;ykaul@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Please review, it's not always just the comments that were fixed.
I've had to revert of course all calls to creat() that were changed
to create() ...

Only compile-tested!

Change-Id: I7d02e82d9766e272a7fd9cc68e51901d69e5aab5
updates: bz#1193929
Signed-off-by: Yaniv Kaul &lt;ykaul@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Use RTLD_LOCAL for symbol resolution</title>
<updated>2017-12-27T15:49:49+00:00</updated>
<author>
<name>Prashanth Pai</name>
<email>ppai@redhat.com</email>
</author>
<published>2017-12-19T17:05:53+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=c6aad575171d4749d1ef2b5fc7c9fd7c32c1c59f'/>
<id>c6aad575171d4749d1ef2b5fc7c9fd7c32c1c59f</id>
<content type='text'>
RTLD_LOCAL is the default value for symbol visibility flag of dlopen()
in Linux and NetBSD. Using it avoids conflicts during symbol resolution.

This also allows us to detect xlators that have not been explicitly
linked with libraries that they use. This used to go unnoticed
when RTLD_GLOBAL was being used.

BUG: 1193929
Change-Id: I50db6ea14ffdee96596060c4d6bf71cd3c432f7b
Signed-off-by: Prashanth Pai &lt;ppai@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
RTLD_LOCAL is the default value for symbol visibility flag of dlopen()
in Linux and NetBSD. Using it avoids conflicts during symbol resolution.

This also allows us to detect xlators that have not been explicitly
linked with libraries that they use. This used to go unnoticed
when RTLD_GLOBAL was being used.

BUG: 1193929
Change-Id: I50db6ea14ffdee96596060c4d6bf71cd3c432f7b
Signed-off-by: Prashanth Pai &lt;ppai@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>glusterfs: Use gcc builtin ATOMIC operator to increase/decreate refcount.</title>
<updated>2017-12-12T09:05:56+00:00</updated>
<author>
<name>Mohit Agrawal</name>
<email>moagrawa@redhat.com</email>
</author>
<published>2017-10-20T07:09:29+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=430484c92ab5a6234958d1143e0bb14aeb0cd1c0'/>
<id>430484c92ab5a6234958d1143e0bb14aeb0cd1c0</id>
<content type='text'>
Problem: In glusterfs code base we call mutex_lock/unlock to take
         reference/dereference for a object.Sometime it could be
         reason for lock contention also.

Solution: There is no need to use mutex to increase/decrease ref
          counter, instead of using mutex use gcc builtin ATOMIC
          operation.

Test:   I have not observed yet how much performance gain after apply
        this patch specific to glusterfs but i have tested same
        with below small program(mutex and atomic both) and
        get good difference.

static int numOuterLoops;
static void *
threadFunc(void *arg)
{
    int j;

    for (j = 0; j &lt; numOuterLoops; j++) {
            __atomic_add_fetch (&amp;glob, 1,__ATOMIC_ACQ_REL);
    }
    return NULL;
}

int
main(int argc, char *argv[])
{
    int opt, s, j;
    int numThreads;
    pthread_t *thread;
    int verbose;
    int64_t n = 0;

    if (argc &lt; 2 ) {
     printf(" Please provide 2 args Num of threads &amp;&amp; Outer Loop\n");
     exit (-1);
    }
    numThreads = atoi(argv[1]);
    numOuterLoops = atoi (argv[2]);

    if (1) {
        printf("\tthreads: %d; outer loops: %d;\n",
                numThreads, numOuterLoops);
    }

    thread = calloc(numThreads, sizeof(pthread_t));
    if (thread == NULL) {
        printf ("calloc error so exit\n");
        exit (-1);
    }

    __atomic_store (&amp;glob, &amp;n, __ATOMIC_RELEASE);
    for (j = 0; j &lt; numThreads; j++) {
        s = pthread_create(&amp;thread[j], NULL, threadFunc, NULL);
        if (s != 0) {
            printf ("pthread_create failed so exit\n");
            exit (-1);
        }
    }

    for (j = 0; j &lt; numThreads; j++) {
        s = pthread_join(thread[j], NULL);
        if (s != 0) {
            printf ("pthread_join failed so exit\n");
            exit (-1);
        }
    }
    printf("glob value is %ld\n",__atomic_load_n (&amp;glob,__ATOMIC_RELAXED));

    exit(0);
}

   time ./thr_count 800 800000
   threads: 800; outer loops: 800000;
   glob value is 640000000

real	1m10.288s
user	0m57.269s
sys	3m31.565s

time ./thr_count_atomic 800 800000
     threads: 800; outer loops: 800000;
glob value is 640000000

real	0m20.313s
user	1m20.558s
sys	0m0.028

Change-Id: Ie5030a52ea264875e002e108dd4b207b15ab7cc7
Signed-off-by: Mohit Agrawal &lt;moagrawa@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Problem: In glusterfs code base we call mutex_lock/unlock to take
         reference/dereference for a object.Sometime it could be
         reason for lock contention also.

Solution: There is no need to use mutex to increase/decrease ref
          counter, instead of using mutex use gcc builtin ATOMIC
          operation.

Test:   I have not observed yet how much performance gain after apply
        this patch specific to glusterfs but i have tested same
        with below small program(mutex and atomic both) and
        get good difference.

static int numOuterLoops;
static void *
threadFunc(void *arg)
{
    int j;

    for (j = 0; j &lt; numOuterLoops; j++) {
            __atomic_add_fetch (&amp;glob, 1,__ATOMIC_ACQ_REL);
    }
    return NULL;
}

int
main(int argc, char *argv[])
{
    int opt, s, j;
    int numThreads;
    pthread_t *thread;
    int verbose;
    int64_t n = 0;

    if (argc &lt; 2 ) {
     printf(" Please provide 2 args Num of threads &amp;&amp; Outer Loop\n");
     exit (-1);
    }
    numThreads = atoi(argv[1]);
    numOuterLoops = atoi (argv[2]);

    if (1) {
        printf("\tthreads: %d; outer loops: %d;\n",
                numThreads, numOuterLoops);
    }

    thread = calloc(numThreads, sizeof(pthread_t));
    if (thread == NULL) {
        printf ("calloc error so exit\n");
        exit (-1);
    }

    __atomic_store (&amp;glob, &amp;n, __ATOMIC_RELEASE);
    for (j = 0; j &lt; numThreads; j++) {
        s = pthread_create(&amp;thread[j], NULL, threadFunc, NULL);
        if (s != 0) {
            printf ("pthread_create failed so exit\n");
            exit (-1);
        }
    }

    for (j = 0; j &lt; numThreads; j++) {
        s = pthread_join(thread[j], NULL);
        if (s != 0) {
            printf ("pthread_join failed so exit\n");
            exit (-1);
        }
    }
    printf("glob value is %ld\n",__atomic_load_n (&amp;glob,__ATOMIC_RELAXED));

    exit(0);
}

   time ./thr_count 800 800000
   threads: 800; outer loops: 800000;
   glob value is 640000000

real	1m10.288s
user	0m57.269s
sys	3m31.565s

time ./thr_count_atomic 800 800000
     threads: 800; outer loops: 800000;
glob value is 640000000

real	0m20.313s
user	1m20.558s
sys	0m0.028

Change-Id: Ie5030a52ea264875e002e108dd4b207b15ab7cc7
Signed-off-by: Mohit Agrawal &lt;moagrawa@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rpc-lib: coverity fixes</title>
<updated>2017-11-22T16:58:39+00:00</updated>
<author>
<name>Milind Changire</name>
<email>mchangir@redhat.com</email>
</author>
<published>2017-11-22T11:33:11+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=50a480701f4bf6885d3811e245a47d99661695d8'/>
<id>50a480701f4bf6885d3811e245a47d99661695d8</id>
<content type='text'>
Scan URL:
https://download.gluster.org/pub/gluster/glusterfs/static-analysis/master/glusterfs-coverity/2017-11-10-0f524f07/html/

ID: 9                            (BAD_SHIFT)
ID: 58                           (CHECKED_RETURN)
ID: 98                           (DEAD_CODE)
ID: 249, 250, 251, 252           (MIXED_ENUMS)
ID: 289, 297                     (NULL_RETURNS)
ID: 609, 613, 622, 644, 653, 655 (UNUSED_VALUE)
ID: 432                          (RESOURCE_LEAK)

Change-Id: I2349877214dd38b789e08b74be05539f09b751b9
BUG: 789278
Signed-off-by: Milind Changire &lt;mchangir@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Scan URL:
https://download.gluster.org/pub/gluster/glusterfs/static-analysis/master/glusterfs-coverity/2017-11-10-0f524f07/html/

ID: 9                            (BAD_SHIFT)
ID: 58                           (CHECKED_RETURN)
ID: 98                           (DEAD_CODE)
ID: 249, 250, 251, 252           (MIXED_ENUMS)
ID: 289, 297                     (NULL_RETURNS)
ID: 609, 613, 622, 644, 653, 655 (UNUSED_VALUE)
ID: 432                          (RESOURCE_LEAK)

Change-Id: I2349877214dd38b789e08b74be05539f09b751b9
BUG: 789278
Signed-off-by: Milind Changire &lt;mchangir@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>gluster: IPv6 single stack support</title>
<updated>2017-10-24T09:28:08+00:00</updated>
<author>
<name>Kevin Vigor</name>
<email>kvigor@fb.com</email>
</author>
<published>2017-04-28T23:44:29+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=1260ee53b1674234e6f083563bdcd258e46a6faa'/>
<id>1260ee53b1674234e6f083563bdcd258e46a6faa</id>
<content type='text'>
Summary:
- This diff changes all locations in the code to prefer inet6 family
  instead of inet.  This will allow change GlusterFS to operate
  via IPv6 instead of IPv4 for all internal operations while still
  being able to serve (FUSE or NFS) clients via IPv4.
- The changes apply to NFS as well.
- This diff ports D1892990, D1897341 &amp; D1896522 to the 3.8 branch.

Test Plan: Prove tests!

Reviewers: dph, rwareing

Signed-off-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;

Change-Id: I34fdaaeb33c194782255625e00616faf75d60c33
BUG: 1406898
Reviewed-on-3.8-fb: http://review.gluster.org/16059
Reviewed-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;
Tested-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Summary:
- This diff changes all locations in the code to prefer inet6 family
  instead of inet.  This will allow change GlusterFS to operate
  via IPv6 instead of IPv4 for all internal operations while still
  being able to serve (FUSE or NFS) clients via IPv4.
- The changes apply to NFS as well.
- This diff ports D1892990, D1897341 &amp; D1896522 to the 3.8 branch.

Test Plan: Prove tests!

Reviewers: dph, rwareing

Signed-off-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;

Change-Id: I34fdaaeb33c194782255625e00616faf75d60c33
BUG: 1406898
Reviewed-on-3.8-fb: http://review.gluster.org/16059
Reviewed-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;
Tested-by: Shreyas Siravara &lt;sshreyas@fb.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rpc: Remove accidental IPV6 changes</title>
<updated>2017-05-05T11:39:28+00:00</updated>
<author>
<name>Kaushal M</name>
<email>kaushal@redhat.com</email>
</author>
<published>2017-05-04T06:45:09+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=de80a9153e3b681d8b83aa6164c94e2829b9cf49'/>
<id>de80a9153e3b681d8b83aa6164c94e2829b9cf49</id>
<content type='text'>
They snuck in with the HALO patch (07cc8679c)

Change-Id: I8ced6cbb0b49554fc9d348c453d4d5da00f981f6
BUG: 1447953
Signed-off-by: Kaushal M &lt;kaushal@redhat.com&gt;
Reviewed-on: https://review.gluster.org/17174
Smoke: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Niels de Vos &lt;ndevos@redhat.com&gt;
NetBSD-regression: NetBSD Build System &lt;jenkins@build.gluster.org&gt;
CentOS-regression: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Amar Tumballi &lt;amarts@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
They snuck in with the HALO patch (07cc8679c)

Change-Id: I8ced6cbb0b49554fc9d348c453d4d5da00f981f6
BUG: 1447953
Signed-off-by: Kaushal M &lt;kaushal@redhat.com&gt;
Reviewed-on: https://review.gluster.org/17174
Smoke: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Niels de Vos &lt;ndevos@redhat.com&gt;
NetBSD-regression: NetBSD Build System &lt;jenkins@build.gluster.org&gt;
CentOS-regression: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Amar Tumballi &lt;amarts@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Halo Replication feature for AFR translator</title>
<updated>2017-05-02T10:23:53+00:00</updated>
<author>
<name>Kevin Vigor</name>
<email>kvigor@fb.com</email>
</author>
<published>2017-03-21T15:23:25+00:00</published>
<link rel='alternate' type='text/html' href='http://git.gluster.org/cgit/glusterfs.git/commit/?id=07cc8679cdf3b29680f4f105d0222da168d8bfc1'/>
<id>07cc8679cdf3b29680f4f105d0222da168d8bfc1</id>
<content type='text'>
Summary:
Halo Geo-replication is a feature which allows Gluster or NFS clients to write
locally to their region (as defined by a latency "halo" or threshold if you
like), and have their writes asynchronously propagate from their origin to the
rest of the cluster.  Clients can also write synchronously to the cluster
simply by specifying a halo-latency which is very large (e.g. 10seconds) which
will include all bricks.

In other words, it allows clients to decide at mount time if they desire
synchronous or asynchronous IO into a cluster and the cluster can support both
of these modes to any number of clients simultaneously.

There are a few new volume options due to this feature:
  halo-shd-latency:  The threshold below which self-heal daemons will
  consider children (bricks) connected.

  halo-nfsd-latency: The threshold below which NFS daemons will consider
  children (bricks) connected.

  halo-latency: The threshold below which all other clients will
  consider children (bricks) connected.

  halo-min-replicas: The minimum number of replicas which are to
  be enforced regardless of latency specified in the above 3 options.
  If the number of children falls below this threshold the next
  best (chosen by latency) shall be swapped in.

New FUSE mount options:
  halo-latency &amp; halo-min-replicas: As descripted above.

This feature combined with multi-threaded SHD support (D1271745) results in
some pretty cool geo-replication possibilities.

Operational Notes:
- Global consistency is gaurenteed for synchronous clients, this is provided by
  the existing entry-locking mechanism.
- Asynchronous clients on the other hand and merely consistent to their region.
  Writes &amp; deletes will be protected via entry-locks as usual preventing
  concurrent writes into files which are undergoing replication.  Read operations
  on the other hand should never block.
- Writes are allowed from _any_ region and propagated from the origin to all
  other regions.  The take away from this is care should be taken to ensure
  multiple writers do not write the same files resulting in a gfid split-brain
  which will require resolution via split-brain policies (majority, mtime &amp;
  size).  Recommended method for preventing this is using the nfs-auth feature to
  define which region for each share has RW permissions, tiers not in the origin
  region should have RO perms.

TODO:
- Synchronous clients (including the SHD) should choose clients from their own
  region as preferred sources for reads.  Most of the plumbing is in place for
  this via the child_latency array.
- Better GFID split brain handling &amp; better dent type split brain handling
  (i.e. create a trash can and move the offending files into it).
- Tagging in addition to latency as a means of defining which children you wish
  to synchronously write to

Test Plan:
- The usual suspects, clang, gcc w/ address sanitizer &amp; valgrind
- Prove tests

Reviewers: jackl, dph, cjh, meyering

Reviewed By: meyering

Subscribers: ethanr

Differential Revision: https://phabricator.fb.com/D1272053

Tasks: 4117827

Change-Id: I694a9ab429722da538da171ec528406e77b5e6d1
BUG: 1428061
Signed-off-by: Kevin Vigor &lt;kvigor@fb.com&gt;
Reviewed-on: http://review.gluster.org/16099
Reviewed-on: https://review.gluster.org/16177
Tested-by: Pranith Kumar Karampuri &lt;pkarampu@redhat.com&gt;
Smoke: Gluster Build System &lt;jenkins@build.gluster.org&gt;
NetBSD-regression: NetBSD Build System &lt;jenkins@build.gluster.org&gt;
CentOS-regression: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Pranith Kumar Karampuri &lt;pkarampu@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Summary:
Halo Geo-replication is a feature which allows Gluster or NFS clients to write
locally to their region (as defined by a latency "halo" or threshold if you
like), and have their writes asynchronously propagate from their origin to the
rest of the cluster.  Clients can also write synchronously to the cluster
simply by specifying a halo-latency which is very large (e.g. 10seconds) which
will include all bricks.

In other words, it allows clients to decide at mount time if they desire
synchronous or asynchronous IO into a cluster and the cluster can support both
of these modes to any number of clients simultaneously.

There are a few new volume options due to this feature:
  halo-shd-latency:  The threshold below which self-heal daemons will
  consider children (bricks) connected.

  halo-nfsd-latency: The threshold below which NFS daemons will consider
  children (bricks) connected.

  halo-latency: The threshold below which all other clients will
  consider children (bricks) connected.

  halo-min-replicas: The minimum number of replicas which are to
  be enforced regardless of latency specified in the above 3 options.
  If the number of children falls below this threshold the next
  best (chosen by latency) shall be swapped in.

New FUSE mount options:
  halo-latency &amp; halo-min-replicas: As descripted above.

This feature combined with multi-threaded SHD support (D1271745) results in
some pretty cool geo-replication possibilities.

Operational Notes:
- Global consistency is gaurenteed for synchronous clients, this is provided by
  the existing entry-locking mechanism.
- Asynchronous clients on the other hand and merely consistent to their region.
  Writes &amp; deletes will be protected via entry-locks as usual preventing
  concurrent writes into files which are undergoing replication.  Read operations
  on the other hand should never block.
- Writes are allowed from _any_ region and propagated from the origin to all
  other regions.  The take away from this is care should be taken to ensure
  multiple writers do not write the same files resulting in a gfid split-brain
  which will require resolution via split-brain policies (majority, mtime &amp;
  size).  Recommended method for preventing this is using the nfs-auth feature to
  define which region for each share has RW permissions, tiers not in the origin
  region should have RO perms.

TODO:
- Synchronous clients (including the SHD) should choose clients from their own
  region as preferred sources for reads.  Most of the plumbing is in place for
  this via the child_latency array.
- Better GFID split brain handling &amp; better dent type split brain handling
  (i.e. create a trash can and move the offending files into it).
- Tagging in addition to latency as a means of defining which children you wish
  to synchronously write to

Test Plan:
- The usual suspects, clang, gcc w/ address sanitizer &amp; valgrind
- Prove tests

Reviewers: jackl, dph, cjh, meyering

Reviewed By: meyering

Subscribers: ethanr

Differential Revision: https://phabricator.fb.com/D1272053

Tasks: 4117827

Change-Id: I694a9ab429722da538da171ec528406e77b5e6d1
BUG: 1428061
Signed-off-by: Kevin Vigor &lt;kvigor@fb.com&gt;
Reviewed-on: http://review.gluster.org/16099
Reviewed-on: https://review.gluster.org/16177
Tested-by: Pranith Kumar Karampuri &lt;pkarampu@redhat.com&gt;
Smoke: Gluster Build System &lt;jenkins@build.gluster.org&gt;
NetBSD-regression: NetBSD Build System &lt;jenkins@build.gluster.org&gt;
CentOS-regression: Gluster Build System &lt;jenkins@build.gluster.org&gt;
Reviewed-by: Pranith Kumar Karampuri &lt;pkarampu@redhat.com&gt;
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