performance/readdir-ahead: keep stats of cached dentries in sync with modifications

PROBLEM:

Stats of dentries that are readdirp'd ahead can become stale due to
fops like writes, truncate etc that modify the file pointed by
dentries. When a readdir is finally wound at offset corresponding to
these entries, the iatts that are returned to the application come
from readdir-ahead's cache, which are stale by now. This problem gets
further aggravated when caching translators/modules cache and continue
to serve this stale information.

FIX:

* Store the iatt in context of the inode pointed by dentry.
* Whenever the inode pointed by dentry undergoes modification, in cbk
  of modification fop, update the iatt stored in inode-ctx to reflect
  the modification.
* When serving a readdirp response from application, update iatts of
  dentries with the iatts stored in the context of inodes pointed by
  these dentries.
* Some fops don't have valid iatts in their responses. For eg., write
  response whose data is still cached in write-behind will have zeroed
  out stat. In this case keep only ia_type and ia_gfid and reset rest
  of the iatt members to zero.
  - fuse-bridge in this case just sends "entry" information back to
    kernel and attr is not sent.
  - gfapi sets entry->inode to NULL and zeroes out the entire stat
* There is one tiny race between the entry creation and a readdirp on
  its parent dir, which could cause the inode-ctx setting and inode
  ctx reading to happen on two different inode objects. To prevent
  this, when entry->inode doesn't eqaul to linked_inode,
  - fuse-bridge is made to send only "entry" information without
    attributes
  - gfapi sets entry->inode to NULL and zeroes out the entire stat.

Change-Id: Ia27ff49a61922e88c73a1547ad8aacc9968a69df
BUG: 1390050
Updates: bz#1390050
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Signed-off-by: Raghavendra G <rgowdapp@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/xlators/cluster/dht/src/dht-common.c b/xlators/cluster/dht/src/dht-common.c
index afec1889071..055c92fcbfc 100644
--- a/xlators/cluster/dht/src/dht-common.c
+++ b/xlators/cluster/dht/src/dht-common.c
@@ -6336,9 +6336,9 @@ dht_file_removexattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 
 out:
         if (local->fop == GF_FOP_REMOVEXATTR) {
-                DHT_STACK_UNWIND (removexattr, frame, op_ret, op_errno, NULL);
+                DHT_STACK_UNWIND (removexattr, frame, op_ret, op_errno, xdata);
         } else {
-                DHT_STACK_UNWIND (fremovexattr, frame, op_ret, op_errno, NULL);
+                DHT_STACK_UNWIND (fremovexattr, frame, op_ret, op_errno, xdata);
         }
         return 0;