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, 13 insertions, 4 deletions

diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
index 20f015431a0..ee50329f03b 100644
--- a/xlators/mount/fuse/src/fuse-bridge.c
+++ b/xlators/mount/fuse/src/fuse-bridge.c
@@ -3056,6 +3056,10 @@ fuse_readdirp_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 		if (!linked_inode)
 			goto next_entry;
 
+                if (entry->inode != linked_inode) {
+                        memset (&entry->d_stat, 0, sizeof (entry->d_stat));
+                }
+
 		feo->nodeid = inode_to_fuse_nodeid (linked_inode);
 
                 if (!((strcmp (entry->d_name, ".") == 0) ||
@@ -3069,10 +3073,15 @@ fuse_readdirp_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
 			calc_timeout_sec (priv->entry_timeout);
 		feo->entry_valid_nsec =
 			calc_timeout_nsec (priv->entry_timeout);
-		feo->attr_valid =
-			calc_timeout_sec (priv->attribute_timeout);
-		feo->attr_valid_nsec =
-			calc_timeout_nsec (priv->attribute_timeout);
+
+                if (entry->d_stat.ia_ctime) {
+                        feo->attr_valid =
+                                calc_timeout_sec (priv->attribute_timeout);
+                        feo->attr_valid_nsec =
+                                calc_timeout_nsec (priv->attribute_timeout);
+                } else {
+                        feo->attr_valid = feo->attr_valid_nsec = 0;
+                }
 
 next_entry:
                 if (size == max_size)