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@redhat.com>
> Reviewed-on: https://review.gluster.org/17115
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
> Signed-off-by: Susant Palai <spalai@redhat.com>

Change-Id: I9854cdd4955d9e24494f348fb29ba856ea7ac50a
BUG: 1473140
Signed-off-by: Susant Palai <spalai@redhat.com>
Reviewed-on: https://review.gluster.org/17837
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>

4 files changed, 35 insertions, 20 deletions

diff --git a/xlators/cluster/dht/src/dht-common.c b/xlators/cluster/dht/src/dht-common.c
index c0da25613d2..7504a46d871 100644
--- a/xlators/cluster/dht/src/dht-common.c
+++ b/xlators/cluster/dht/src/dht-common.c
@@ -4170,6 +4170,9 @@ dht_setxattr (call_frame_t *frame, xlator_t *this,
                         goto err;
                 }
 
+                if (gf_uuid_is_null (local->loc.pargfid))
+                        gf_uuid_copy (local->loc.pargfid, local->loc.parent->gfid);
+
                 methods->migration_get_dst_subvol(this, local);
 
                 if (!local->rebalance.target_node) {
diff --git a/xlators/cluster/dht/src/dht-common.h b/xlators/cluster/dht/src/dht-common.h
index 6f0dd774181..c2583e4f962 100644
--- a/xlators/cluster/dht/src/dht-common.h
+++ b/xlators/cluster/dht/src/dht-common.h
@@ -501,9 +501,6 @@ struct gf_defrag_info_ {
         int32_t                      current_thread_count;
         pthread_cond_t               df_wakeup_thread;
 
-        /* Hard link handle requirement */
-        synclock_t                   link_lock;
-
         /* lock migration flag */
         gf_boolean_t                 lock_migration_enabled;
 
@@ -604,6 +601,10 @@ struct dht_conf {
 
         gf_boolean_t    lock_migration_enabled;
         gf_lock_t       lock;
+
+        /* Hard link handle requirement for migration triggered from client*/
+        synclock_t      link_lock;
+
 };
 typedef struct dht_conf dht_conf_t;
 
diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index 9d6858cb535..30d8d878be8 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -495,7 +495,7 @@ out:
 static int
 __check_file_has_hardlink (xlator_t *this, loc_t *loc,
                            struct iatt *stbuf, dict_t *xattrs, int flags,
-                           gf_defrag_info_t *defrag, int *fop_errno)
+                           gf_defrag_info_t *defrag, dht_conf_t *conf, int *fop_errno)
 {
        int ret = 0;
 
@@ -506,10 +506,10 @@ __check_file_has_hardlink (xlator_t *this, loc_t *loc,
        if (stbuf->ia_nlink > 1) {
                 /* support for decomission */
                 if (flags == GF_DHT_MIGRATE_HARDLINK) {
-                        synclock_lock (&defrag->link_lock);
+                        synclock_lock (&conf->link_lock);
                         ret = gf_defrag_handle_hardlink
                                 (this, loc, xattrs, stbuf, fop_errno);
-                        synclock_unlock (&defrag->link_lock);
+                        synclock_unlock (&conf->link_lock);
                         /*
                         Returning zero will force the file to be remigrated.
                         Checkout gf_defrag_handle_hardlink for more information.
@@ -546,7 +546,8 @@ __check_file_has_hardlink (xlator_t *this, loc_t *loc,
 static int
 __is_file_migratable (xlator_t *this, loc_t *loc,
                       struct iatt *stbuf, dict_t *xattrs, int flags,
-                                gf_defrag_info_t *defrag, int *fop_errno)
+                      gf_defrag_info_t *defrag, dht_conf_t *conf,
+                      int *fop_errno)
 {
         int ret = -1;
         int lock_count = 0;
@@ -561,7 +562,7 @@ __is_file_migratable (xlator_t *this, loc_t *loc,
                 goto out;
         }
 
-        if (!defrag->lock_migration_enabled) {
+        if (!conf->lock_migration_enabled) {
                 ret = dict_get_int32 (xattrs, GLUSTERFS_POSIXLK_COUNT,
                                       &lock_count);
                 if (ret) {
@@ -588,7 +589,7 @@ __is_file_migratable (xlator_t *this, loc_t *loc,
 
         /* Check if file has hardlink*/
         ret = __check_file_has_hardlink (this, loc, stbuf, xattrs,
-                                         flags, defrag, fop_errno);
+                                         flags, defrag, conf, fop_errno);
 out:
         return ret;
 }
@@ -1493,11 +1494,19 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         fd_t                    *linkto_fd              = NULL;
         gf_boolean_t            ignore_failure          = _gf_false;
 
+
+        /* If defrag is NULL, it should be assumed that migration is triggered
+         * from client */
         defrag = conf->defrag;
-        if (!defrag)
+
+        /* migration of files from clients is restricted to non-tiered clients
+         * for now */
+        if (!defrag && dht_is_tier_xlator (this)) {
+                ret = ENOTSUP;
                 goto out;
+        }
 
-        if (defrag->tier_conf.is_tier)
+        if (defrag && defrag->tier_conf.is_tier)
                 log_level = GF_LOG_TRACE;
 
         gf_log (this->name,
@@ -1526,7 +1535,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
         /* Do not migrate file in case lock migration is not enabled on the
          * volume*/
-        if (!defrag->lock_migration_enabled) {
+        if (!conf->lock_migration_enabled) {
                 ret = dict_set_int32 (dict,
                                  GLUSTERFS_POSIXLK_COUNT, sizeof(int32_t));
                 if (ret) {
@@ -1582,7 +1591,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         src_ia_prot = stbuf.ia_prot;
 
         /* Check if file can be migrated */
-        ret = __is_file_migratable (this, loc, &stbuf, xattr_rsp, flag, defrag,
+        ret = __is_file_migratable (this, loc, &stbuf, xattr_rsp, flag, defrag, conf,
                                     fop_errno);
         if (ret) {
                 if (ret == -2)
@@ -1702,7 +1711,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
         /* Check again if file has hardlink */
         ret = __check_file_has_hardlink (this, loc, &stbuf, xattr_rsp,
-                                         flag, defrag, fop_errno);
+                                         flag, defrag, conf, fop_errno);
         if (ret) {
                 if (ret == -2)
                         ret = 0;
@@ -1714,7 +1723,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
 
         /* All I/O happens in this function */
-        if (defrag->cmd == GF_DEFRAG_CMD_START_TIER) {
+        if (defrag && defrag->cmd == GF_DEFRAG_CMD_START_TIER) {
                 ret = __tier_migrate_data (defrag, from, to, src_fd, dst_fd,
                                                     stbuf.ia_size,
                                                     file_has_holes, fop_errno);
@@ -1773,7 +1782,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
         /* Take meta lock  */
 
-        if (defrag->lock_migration_enabled) {
+        if (conf->lock_migration_enabled) {
                 meta_dict = dict_new ();
                 if (!meta_dict) {
                         gf_msg (this->name, GF_LOG_ERROR, 0,
@@ -1821,7 +1830,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
                 }
         }
 
-        if (!defrag->lock_migration_enabled) {
+        if (!conf->lock_migration_enabled) {
                 plock.l_type = F_WRLCK;
                 plock.l_start = 0;
                 plock.l_len = 0;
@@ -2019,7 +2028,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         }
 
         /* store size of previous migrated file  */
-        if (defrag->tier_conf.is_tier) {
+        if (defrag && defrag->tier_conf.is_tier) {
                 if (from != TIER_HASHED_SUBVOL) {
                         defrag->tier_conf.st_last_promoted_size = stbuf.ia_size;
                 } else {
@@ -2129,7 +2138,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
 metaunlock:
 
-        if (defrag->lock_migration_enabled && meta_locked) {
+        if (conf->lock_migration_enabled && meta_locked) {
 
                 dict_del (meta_dict, GF_META_LOCK_KEY);
 
diff --git a/xlators/cluster/dht/src/dht-shared.c b/xlators/cluster/dht/src/dht-shared.c
index 96b9699f228..f84b40a8d91 100644
--- a/xlators/cluster/dht/src/dht-shared.c
+++ b/xlators/cluster/dht/src/dht-shared.c
@@ -241,6 +241,8 @@ dht_fini (xlator_t *this)
 
                 GF_FREE (conf->subvolume_status);
 
+                synclock_destroy (&conf->link_lock);
+
                 if (conf->lock_pool)
                         mem_pool_destroy (conf->lock_pool);
 
@@ -678,6 +680,7 @@ dht_init (xlator_t *this)
         LOCK_INIT (&conf->subvolume_lock);
         LOCK_INIT (&conf->layout_lock);
         LOCK_INIT (&conf->lock);
+        synclock_init (&conf->link_lock, SYNC_LOCK_DEFAULT);
 
         /* We get the commit-hash to set only for rebalance process */
         if (dict_get_uint32 (this->options,
@@ -733,7 +736,6 @@ dht_init (xlator_t *this)
 
                 defrag->wakeup_crawler = 0;
 
-                synclock_init (&defrag->link_lock, SYNC_LOCK_DEFAULT);
                 pthread_mutex_init (&defrag->dfq_mutex, 0);
                 pthread_cond_init  (&defrag->parallel_migration_cond, 0);
                 pthread_cond_init  (&defrag->rebalance_crawler_alarm, 0);