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

Backport of https://review.gluster.org/19045

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: 1566131
Signed-off-by: karthik-us <ksubrahm@redhat.com>
Signed-off-by: Ravishankar N <ravishankar@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/xlators/cluster/afr/src/afr-messages.h b/xlators/cluster/afr/src/afr-messages.h
index 02eb206fd08..39b22ff1270 100644
--- a/xlators/cluster/afr/src/afr-messages.h
+++ b/xlators/cluster/afr/src/afr-messages.h
@@ -369,5 +369,12 @@
 */
 #define AFR_MSG_SBRAIN_FAV_CHILD_POLICY  (GLFS_COMP_BASE_AFR + 42)
 
+/*!
+ * @messageid 108025
+ * @diagnosis
+ * @recommendedaction
+*/
+#define AFR_MSG_INODE_CTX_GET_FAILED     (GLFS_COMP_BASE_AFR + 43)
+
 #define glfs_msg_end_x GLFS_MSGID_END, "Invalid: End of messages"
 #endif /* !_AFR_MESSAGES_H_ */