afr: Avoid resetting event_gen when brick is always down

Problem:
__afr_set_in_flight_sb_status(), which resets event_gen to zero, is
called if failed_subvols[i] is non-zero for any brick. But failed_subvols[i]
is true even if the brick was down *before* the transaction started.
Hence say if 1 brick is down in  a replica-3, every writev that comes
will trigger an inode refresh because of this resetting, as seen from
the no. of FSTATs in the profile info in the BZ.

Fix:
Reset event gen only if the brick was previously a valid read child and
the FOP failed on it the first time.

Also `s/afr_inode_read_subvol_reset/afr_inode_event_gen_reset` because
the function only resets event gen and not the data/metadata readable.

> Signed-off-by: Ravishankar N <ravishankar@redhat.com>
> Reviewed-on: http://review.gluster.org/16309
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
> Tested-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
(cherry picked from commit 522640be476a3f97dac932f7046f0643ec0ec2f2)

Change-Id: I603ae646cbde96995c35db77916e2ed80b602a91
BUG: 1412886
Reviewed-on: http://review.gluster.org/16385
Tested-by: Ravishankar N <ravishankar@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>

1 files changed, 1 insertions, 5 deletions

diff --git a/xlators/cluster/afr/src/afr.h b/xlators/cluster/afr/src/afr.h
index 642d633f9c4..e1df803c172 100644
--- a/xlators/cluster/afr/src/afr.h
+++ b/xlators/cluster/afr/src/afr.h
@@ -882,7 +882,7 @@ afr_inode_read_subvol_set (inode_t *inode, xlator_t *this,
 			   int event_generation);
 
 int
-afr_inode_read_subvol_reset (inode_t *inode, xlator_t *this);
+afr_inode_event_gen_reset (inode_t *inode, xlator_t *this);
 
 int
 afr_read_subvol_select_by_policy (inode_t *inode, xlator_t *this,
@@ -906,10 +906,6 @@ afr_read_subvol_get (inode_t *inode, xlator_t *this, int *subvol_p,
 	afr_read_subvol_get(i, t, s, r, e, AFR_METADATA_TRANSACTION, a)
 
 int
-afr_inode_ctx_reset_unreadable_subvol (inode_t *inode, xlator_t *this,
-                                       int subvol_idx, int txn_type);
-
-int
 afr_inode_refresh (call_frame_t *frame, xlator_t *this, inode_t *inode,
                    uuid_t gfid, afr_inode_refresh_cbk_t cbk);