[Bugs] [Bug 1515572] New: Accessing a file when source brick is down results in that FOP being hung

Tue Nov 21 04:11:01 UTC 2017

https://bugzilla.redhat.com/show_bug.cgi?id=1515572

            Bug ID: 1515572
           Summary: Accessing a file when source brick is down results in
                    that FOP being hung
           Product: GlusterFS
           Version: 3.13
         Component: replicate
          Keywords: Triaged
          Assignee: bugs at gluster.org
          Reporter: ravishankar at redhat.com
                CC: bugs at gluster.org
        Depends On: 1467250
            Blocks: 1467247

+++ This bug was initially created as a clone of Bug #1467250 +++

This was a hyper converged setup with arbiter volume:

Volume Name: arbvol
Type: Replicate
Volume ID: d7ccfadd-63e1-4fef-b70f-77d0e2cb2bba
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x (2 + 1) = 3
Transport-type: tcp
Bricks:
Brick1: node1:/gluster/brick1/b1
Brick2: node2:/gluster/brick1/b1
Brick3: node3:/gluster/brick1/b1 (arbiter)
Options Reconfigured:
cluster.self-heal-daemon: off
performance.strict-o-direct: on
cluster.granular-entry-heal: enable
network.ping-timeout: 10
user.cifs: off
features.shard: on
cluster.shd-wait-qlength: 10000
cluster.shd-max-threads: 8
cluster.locking-scheme: granular
cluster.data-self-heal-algorithm: full
cluster.server-quorum-type: server
cluster.quorum-type: auto
cluster.eager-lock: on
network.remote-dio: off
performance.low-prio-threads: 32
performance.stat-prefetch: off
performance.io-cache: off
performance.read-ahead: off
performance.quick-read: off
transport.address-family: inet
nfs.disable: on
cluster.data-self-heal: off
cluster.metadata-self-heal: off
cluster.entry-self-heal: off

In a hc setup, writes, truncates and reads were happening from a single client
while the bricks were continuously being killed and brought backup one by one
in a loop. I/O was then getting hung from the mount.

gdb back trace  of mount:
#3  0x00007f45a762f5ee in shard_make_block_abspath (block_num=159197526,
gfid=0x7f45a805a0a8 "$r\342\366{\260E\032\251\020\254>\312B\245\274",
filepath=0x7f45ac9e1f90
"/.shard/2472e2f6-7bb0-451a-a910-ac3eca42a5bc.159197525", len=4096)
    at shard.c:57
#4  0x00007f45a7632605 in shard_common_resolve_shards (frame=0x7f45a8000b60,
this=0x7f45a80121e0, post_res_handler=0x7f45a763a344
<shard_post_resolve_truncate_handler>) at shard.c:635
#5  0x00007f45a763337b in shard_refresh_dot_shard (frame=0x7f45a8000b60,
this=0x7f45a80121e0) at shard.c:884
#6  0x00007f45a763b2a4 in shard_truncate_begin (frame=0x7f45a8000b60,
this=0x7f45a80121e0) at shard.c:1989
#7  0x00007f45a763c7e3 in shard_post_lookup_truncate_handler
(frame=0x7f45a8000b60, this=0x7f45a80121e0) at shard.c:2063
#8  0x00007f45a7634b79 in shard_lookup_base_file_cbk (frame=0x7f45a8000b60,
cookie=0x7f45a804e130, this=0x7f45a80121e0, op_ret=0, op_errno=117,
inode=0x7f45a805a0a0, buf=0x7f45a804ee68, xdata=0x7f45a8071ad0,
postparent=0x7f45a804f098)
    at shard.c:1149
#9  0x00007f45a7892dd4 in dht_discover_complete (this=0x7f45a8010ab0,
discover_frame=0x7f45a8060f60) at dht-common.c:577
#10 0x00007f45a78937f1 in dht_discover_cbk (frame=0x7f45a8060f60,
cookie=0x7f45a800de50, this=0x7f45a8010ab0, op_ret=0, op_errno=117,
inode=0x7f45a805a0a0, stbuf=0x7f45a807d890, xattr=0x7f45a8071ad0,
postparent=0x7f45a807d900)
    at dht-common.c:700
#11 0x00007f45a7b71ad6 in afr_discover_done (frame=0x7f45a8066d60,
this=0x7f45a800de50) at afr-common.c:2624
#12 0x00007f45a7b71e19 in afr_discover_cbk (frame=0x7f45a8066d60, cookie=0x2,
this=0x7f45a800de50, op_ret=0, op_errno=0, inode=0x7f45a805a0a0,
buf=0x7f45ac9e3900, xdata=0x7f45a806cb50, postparent=0x7f45ac9e3890) at
afr-common.c:2669

shard_common_resolve_shards() was stuck in while (shard_idx_iter <=
local->last_block) because local->last_block was -1. Turns out afr served the
lookup from a bad copy (the good brick was down) and shard used the iatt values
in the lookup cbk to calculate size and block count which were not correct.

xattr values of the FILE on the bad brick from which lookup was served:

[root at node2]# g /gluster/brick1/b1/FILE 
getfattr: Removing leading '/' from absolute path names
# file: gluster/brick1/b1/FILE
security.selinux=0x73797374656d5f753a6f626a6563745f723a676c7573746572645f627269636b5f743a733000
trusted.afr.arbvol-client-2=0x000003e00000046700000000
trusted.afr.dirty=0x000000020000012e00000000
trusted.gfid=0x0e47074be70b4c25bdf2f5d40a26a049
trusted.glusterfs.shard.block-size=0x0000000000400000
trusted.glusterfs.shard.file-size=0xfffffffffff214000000000000000000fffffffffffff80a0000000000000000

--- Additional comment from Worker Ant on 2017-07-03 05:03:05 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#1) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-07-04 22:45:20 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#2) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-07-06 01:51:02 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#3) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-08-27 08:47:59 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#4) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-09-06 12:56:05 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#5) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-09-13 05:32:19 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#6) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-10-17 08:17:43 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#7) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-10-18 02:25:40 EDT ---

REVIEW: https://review.gluster.org/17673 (afr: add checks for allowing lookups)
posted (#8) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Worker Ant on 2017-11-17 19:39:24 EST ---

COMMIT: https://review.gluster.org/17673 committed in master by \"Ravishankar
N\" <ravishankar at redhat.com> with a commit message- afr: add checks for
allowing lookups

Problem:
In an arbiter volume, lookup was being served from one of the sink
bricks (source brick was down). shard uses the iatt values from lookup cbk
to calculate the size and block count, which in this case were incorrect
values. shard_local_t->last_block was thus initialised to -1, resulting
in an infinite while loop in shard_common_resolve_shards().

Fix:
Use client quorum logic to allow or fail the lookups from afr if there
are no readable subvolumes. So in replica-3 or arbiter vols, if there is
no good copy or if quorum is not met, fail lookup with ENOTCONN.

With this fix, we are also removing support for quorum-reads xlator
option. So if quorum is not met, neither read nor write txns are allowed
and we fail the fop with ENOTCONN.

Change-Id: Ic65c00c24f77ece007328b421494eee62a505fa0
BUG: 1467250
Signed-off-by: Ravishankar N <ravishankar at redhat.com>

Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1467247
[Bug 1467247] Accessing a file when source brick is down results in  that
FOP being hung
https://bugzilla.redhat.com/show_bug.cgi?id=1467250
[Bug 1467250] Accessing a file when source brick is down results in  that
FOP being hung
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