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, 49 insertions, 3 deletions

diff --git a/xlators/performance/readdir-ahead/src/readdir-ahead.h b/xlators/performance/readdir-ahead/src/readdir-ahead.h
index 3c06cc0f107..7dbed4c60ed 100644
--- a/xlators/performance/readdir-ahead/src/readdir-ahead.h
+++ b/xlators/performance/readdir-ahead/src/readdir-ahead.h
@@ -19,6 +19,44 @@
 #define RDA_FD_BYPASS	(1 << 4)
 #define RDA_FD_PLUGGED	(1 << 5)
 
+
+#define RDA_COMMON_MODIFICATION_FOP(name, frame, this, __inode, __xdata, args ...)\
+        do {                                                                   \
+                struct rda_local *__local = NULL;                              \
+                rda_inode_ctx_t  *ctx_p   = NULL;                              \
+                                                                               \
+                __local = mem_get0 (this->local_pool);                         \
+                __local->inode = inode_ref (__inode);                          \
+                LOCK (&__inode->lock);                                         \
+                {                                                              \
+                        ctx_p = __rda_inode_ctx_get (__inode, this);           \
+                }                                                              \
+                UNLOCK (&__inode->lock);                                       \
+                __local->generation   = GF_ATOMIC_GET (ctx_p->generation);     \
+                                                                               \
+                frame->local = __local;                                        \
+                if (__xdata)                                                   \
+                        __local->xattrs = dict_ref (__xdata);                  \
+                                                                               \
+                STACK_WIND (frame, rda_##name##_cbk, FIRST_CHILD(this),        \
+                            FIRST_CHILD(this)->fops->name, args, __xdata);     \
+        } while (0)
+
+
+#define RDA_STACK_UNWIND(fop, frame, params ...) do {          \
+        struct rda_local *__local = NULL;                      \
+        if (frame) {                                           \
+                __local = frame->local;                        \
+                frame->local = NULL;                           \
+        }                                                      \
+        STACK_UNWIND_STRICT (fop, frame, params);              \
+        if (__local) {                                         \
+                rda_local_wipe (__local);                      \
+                mem_put (__local);                             \
+        }                                                      \
+} while (0)
+
+
 struct rda_fd_ctx {
 	off_t cur_offset;	/* current head of the ctx */
 	size_t cur_size;	/* current size of the preload */
@@ -34,9 +72,12 @@ struct rda_fd_ctx {
 
 struct rda_local {
 	struct rda_fd_ctx *ctx;
-	fd_t *fd;
-	off_t offset;
-        dict_t *xattrs;      /* xattrs to be sent in readdirp() */
+	fd_t              *fd;
+        dict_t            *xattrs; /* md-cache keys to be sent in readdirp() */
+        inode_t           *inode;
+        off_t              offset;
+        uint64_t           generation;
+        int32_t            skip_dir;
 };
 
 struct rda_priv {
@@ -48,4 +89,9 @@ struct rda_priv {
         gf_boolean_t parallel_readdir;
 };
 
+typedef struct rda_inode_ctx {
+        struct iatt statbuf;
+        gf_atomic_t generation;
+} rda_inode_ctx_t;
+
 #endif /* __READDIR_AHEAD_H */