glusterfs.git/xlators/cluster/afr/src/afr-lk-common.c, branch v4.1.10

cluster/afr: Prevent execution of code after call_count decrementing

2018-07-10T08:49:30+00:00

Problem:
When call_count is decremented by one thread, another thread can
go ahead with the operation leading to undefined behavior for the
thread executing statements after decrementing call count.

Fix:
Do the operations necessary before decrementing call count.

fixes bz#1599629
Change-Id: Icc90cd92ac16e5fbdfe534d9f0a61312943393fe
Signed-off-by: Pranith Kumar K 
(cherry picked from commit 03f1f5bdc46076178f1afdf8e2a76c5b973fe11f)

cluster/afr: Make AFR eager-locking similar to EC

2018-03-14T13:32:35+00:00

Problem:
1) Afr's eager-lock only works for data transactions.
2) When there are conflicting writes, write with conflicting region initiates
unlock of eager-lock leading to extra pre-ops and post-ops on the file. When
eager-lock goes off, it leads to extra fsyncs for random-write workload in afr.

Solution (that is modeled after EC):
In EC, when there is a conflicting write, it waits for the current write to
complete before it winds the conflicted write. This leads to better utilization
of network and disk, because we will not be doing extra xattrops and FSYNCs and
inodelk/unlock. Moved fd based counters to inode based counters.

I tried to model the solution based on EC's locking, but it is not similar to
AFR because we had to keep backward compatibility.

Lifecycle of lock:
==================
First transaction is added to inode->owners list and an inodelk will be sent on
the wire. All the next transactions will be put in inode->waiters list until
the first transaction completes inodelk and [f]xattrop completely.  Once
[f]xattrop also completes, all the requests in the inode->waiters list are
checked if it conflict with any of the existing locks which are in
inode->owners list and if not are added to inode->owners list and resumed with
doing transaction. When these transactions complete fop phase they will be
moved to inode->post_op list and resume the transactions that were paused
because of conflicts. Post-op and unlock will not be issued on the wire until
that is the last transaction on that inode. Last transaction when it has to
perform post-op can choose to sleep for deyed-post-op-secs value. During that
time if any other transaction comes, it will wake up the sleeping transaction
and takes over the ownership of the lock and the cycle continues. If the
dealyed-post-op-secs expire, then the timer thread will wakeup the sleeping
transaction and it will set lock->release to true and starts doing post-op and
then unlock. During this time if any other transactions come, they will be put
in inode->frozen list. Once the previous unlock comes it will move the frozen
list to waiters list and moves the first element from this waiters-list to
owners-list and attempts the lock and the cycle continues. This is the general
idea.  There is logic at the time of dealying and at the time of new
transaction or in flush fop to wakeup existing sleeping transactions or
choosing whether to delay a transaction etc, which is subjected to change based
on future enhancements etc.

Fixes: #418
BUG: 1549606
Change-Id: I88b570bbcf332a27c82d2767dfa82472f60055dc
Signed-off-by: Pranith Kumar K

cluster/afr: Remove unused code paths

2018-03-06T08:49:31+00:00

Removed
1) afr-v1 self-heal locks related code which is not used anymore
2) transaction has some data types that are not needed, so removed them
3) Never used lock tracing available in afr as gluster's network tracing does
the job. So removed that as well.
4) Changelog is always enabled and afr is always used with locks, so
__changelog_enabled, afr_lock_server_count etc functions can be deleted.
5) transaction.fop/done/resume always call the same functions, so no need
to have these variables.

BUG: 1549606
Change-Id: I370c146fec2892d40e674d232a5d7256e003c7f1
Signed-off-by: Pranith Kumar K

cluster/afr: Fixing the flaws in arbiter becoming source patch

2018-01-13T02:55:44+00:00

Problem:
Setting the write_subvol value to read_subvol in case of metadata
transaction during pre-op (commit 19f9bcff4aada589d4321356c2670ed283f02c03)
might lead to the original problem of arbiter becoming source.

Scenario:
1) All bricks are up and good
2) 2 writes w1 and w2 are in progress in parallel
3) ctx->read_subvol is good for all the subvolumes
4) w1 succeeds on brick0 and fails on brick1, yet to do post-op on
   the disk
5) read/lookup comes on the same file and refreshes read_subvols back
   to all good
6) metadata transaction happens which makes ctx->write_subvol to be
   assigned with ctx->read_subvol which is all good
7) w2 succeeds on brick1 and fails on brick0 and this will update the
   brick in reverse order leading to arbiter becoming source

Fix:
Instead of setting the ctx->write_subvol to ctx->read_subvol in the
pre-op statge, if there is a metadata transaction, check in the
function __afr_set_in_flight_sb_status() if it is a data/metadata
transaction. Use the value of ctx->write_subvol if it is a data
transactions and ctx->read_subvol value for other transactions.

With this patch we assign the value of ctx->write_subvol in the
afr_transaction_perform_fop() with the on disk value, instead of
assigning it in the afr_changelog_pre_op() with the in memory value.

Change-Id: Id2025a7e965f0578af35b1abaac793b019c43cc4
BUG: 1482064
Signed-off-by: karthik-us

cluster/afr: Fix for arbiter becoming source

2017-11-18T00:38:20+00:00

Problem:
When eager-lock is on, and two writes happen in parallel on a FD
we were observing the following behaviour:
- First write fails on one data brick
- Since the post-op is not yet happened, the inode refresh will get
  both the data bricks as readable and set it in the inode context
- In flight split brain check see both the data bricks as readable
  and allows the second write
- Second write fails on the other data brick
- Now the post-op happens and marks both the data bricks as bad and
  arbiter will become source for healing

Fix:
Adding one more variable called write_suvol in inode context and it
will have the in memory representation of the writable subvols. Inode
refresh will not update this value and its lifetime is pre-op through
unlock in the afr transaction. Initially the pre-op will set this
value same as read_subvol in inode context and then in the in flight
split brain check we will use this value instead of read_subvol.
After all the checks we will update the value of this and set the
read_subvol same as this to avoid having incorrect value in that.

Change-Id: I2ef6904524ab91af861d59690974bbc529ab1af3
BUG: 1482064
Signed-off-by: karthik-us

cluster/afr: Fix bugs in [f]inodelk/[f]entrylk

2016-11-26T15:34:59+00:00

Problems:
1) Inodelk is not taking quorum into account
2) finodelk, [f]entrylk are not implemented correctly
3) By default afr doesn't go for non-blocking parallel locks.

Fix:
Implemented a common framework which can be used by
[f]inodelk/[f]entrylk.  Used quorum for the same.

Change-Id: I239f13875a065298630d266941df10cfa3addc85
BUG: 1369077
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/15802
Tested-by: Krutika Dhananjay 
Reviewed-by: Krutika Dhananjay 
Smoke: Gluster Build System 
Reviewed-by: Ravishankar N 
CentOS-regression: Gluster Build System 
NetBSD-regression: NetBSD Build System

afr: Consume compound fops in afr transaction

2016-09-01T17:22:39+00:00

Change-Id: Ib06ece3cce1b10d28d6d2953da28444f5c2457ad
BUG: 1290304
Signed-off-by: Anuradha Talur 
Reviewed-on: http://review.gluster.org/15014
Tested-by: Pranith Kumar Karampuri 
Smoke: Gluster Build System 
CentOS-regression: Gluster Build System 
NetBSD-regression: NetBSD Build System 
Reviewed-by: Krutika Dhananjay 
Reviewed-by: Pranith Kumar Karampuri

cluster/afr: Give option to do consistent-io

2016-08-22T20:55:42+00:00

Problem:
When tiering/rebalance does migrations and afr with 2-way replica is in
picture, migration can read stale data if the source brick goes down and writes
to the destination. After this deletion of the file leads to permanent loss of
data after migration.

Fix:
Rebalance/tiering should migrate only when the data is definitely not stale. So
introduce an option in afr called consistent-io which will be enabled in
migration daemons.

BUG: 1306398
Change-Id: I750f65091cc70a3ed4bf3c12f83d0949af43920a
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/13425
Reviewed-by: Anuradha Talur 
Reviewed-by: Krutika Dhananjay 
Smoke: Gluster Build System 
NetBSD-regression: NetBSD Build System 
CentOS-regression: Gluster Build System

cluster/afr: Check for required number of entrylks

2016-05-24T08:23:46+00:00

Problem:
Parallel rmdir operations on the same directory results in ENOTCONN messages
eventhough there was no network disconnect.

In blocking entry lock during rmdir, AFR takes 2 set of locks on all its
children-One (parentdir,name of dir to be deleted), the other (full lock
on the dir being deleted). We proceed to pre-op stage even if only a single
lock (but not all the needed locks) was obtained, only to fail it with ENOTCONN
because afr_locked_nodes_get() returns zero nodes  in afr_changelog_pre_op().

Fix:
After we get replies for all blocking lock requests, if we don't have
the minimum number of locks to carry out the FOP, unlock and fail the
FOP. The op_errno will be that of the last failed reply we got, i.e.
whatever is set in afr_lock_cbk().

Change-Id: Ibef25e65b468ebb5ea6ae1f5121a5f1201072293
BUG: 1336381
Signed-off-by: Ravishankar N 
Reviewed-on: http://review.gluster.org/14358
Reviewed-by: Pranith Kumar Karampuri 
Tested-by: Pranith Kumar Karampuri 
Smoke: Gluster Build System 
NetBSD-regression: NetBSD Build System 
CentOS-regression: Gluster Build System

all: reduce "inline" usage

2015-09-01T11:55:15+00:00

There are three kinds of inline functions: plain inline, extern inline,
and static inline.  All three have been removed from .c files, except
those in "contrib" which aren't our problem.  Inlines in .h files, which
are overwhelmingly "static inline" already, have generally been left
alone.  Over time we should be able to "lower" these into .c files, but
that has to be done in a case-by-case fashion requiring more manual
effort.  This part was easy to do automatically without (as far as I can
tell) any ill effect.

In the process, several pieces of dead code were flagged by the
compiler, and were removed.

Change-Id: I56a5e614735c9e0a6ee420dab949eac22e25c155
BUG: 1245331
Signed-off-by: Jeff Darcy 
Reviewed-on: http://review.gluster.org/11769
Tested-by: NetBSD Build System 
Reviewed-by: Dan Lambright 
Reviewed-by: Kaleb KEITHLEY 
Reviewed-by: Niels de Vos 
Reviewed-by: Raghavendra Bhat 
Reviewed-by: Venky Shankar