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+what is stat-prefetch?
+======================
+It is a translator which caches the dentries read in readdir. This dentry
+list is stored in the context of fd. Later when lookup happens on
+[parent-inode, basename (path)] combination, this list is searched for the
+basename. The dentry thus searched is used to fill up the stat corresponding
+to path being looked upon, thereby short-cutting lookup calls. This cache is
+preserved till closedir is called on the fd. The purpose of this translator
+is to optimize operations like 'ls -l', where a readdir is followed by
+lookup (stat) calls on each directory entry.
+
+1. stat-prefetch harnesses the efficiency of short lookup calls
+   (saves network roundtrip time for lookup calls from being accounted to
+   the stat call).
+2. To maintain the correctness, it does lookup-behind - lookup is winded to
+   underlying translators after it is unwound to upper translators.
+   lookup-behind is necessary as inode gets populated in server inode table
+   only in lookup-cbk and also because various translators store their
+   contexts in inode contexts during lookup calls.
+
+fops to be implemented:
+=======================
+* lookup
+  1. check the dentry cache stored in context of fds opened by the same process
+     on parent inode for basename. If found unwind with cached stat, else wind
+     the lookup call to underlying translators.
+  2. stat is stored in the context of inode if the path being looked upon
+     happens to be directory. This stat will be used to fill postparent stat
+     when lookup happens on any of the directory contents.
+
+* readdir
+  1. cache the direntries returned in readdir_cbk in the context of fd.
+  2. if the readdir is happening on non-expected offsets (means a seekdir/rewinddir
+     has happened), cache has to be flushed.
+  3. delete the entry corresponding to basename of path on which fd is opened
+     from cache stored in parent.
+
+* chmod/fchmod
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since these calls change st_mode and st_ctime of
+  stat.
+
+* chown/fchown
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since these calls change st_uid/st_gid and
+  st_ctime of stat.
+
+* truncate/ftruncate
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since these calls change st_size/st_mtime of stat.
+
+* utimens
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since this call changes st_atime/st_mtime of stat.
+
+* readlink
+  delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since this call changes st_atime of stat.
+
+* unlink
+  1. delete the entry corresponding to basename from cache stored in context of
+     fds, opened on parent directory containing the file being unlinked.
+  2. delete the entry corresponding to basename of parent directory from cache
+     of grand-parent.
+
+* rmdir
+  1. delete the entry corresponding to basename from cache stored in context of
+     fds opened on parent inode.
+  2. remove the entire cache from all fds opened on inode corresponding to
+     directory being removed.
+  3. delete the entry correspondig to basename of parent from cache stored in
+     grand-parent.
+
+* readv
+  delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since readv changes st_atime of file.
+
+* writev
+  delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since writev can possibly change st_size and definitely
+  changes st_mtime of file.
+
+* fsync
+  there is a confusion here as to whether fsync updates mtime/ctimes. Disk based
+  filesystems (atleast ext2) just writes the times stored in inode to disk
+  during fsync and not the time at which fsync is being done. But in glusterfs,
+  a translator like write-behind actually sends writes during fsync which will
+  change mtime/ctime. Hence stat-prefetch implements fsync to delete the entry
+  corresponding to basename from cache stored in context of fds opened on parent
+  inode.
+
+* rename
+  1. remove entry corresponding to oldname from cache stored in fd contexts of
+     oldparent.
+  2. remove entry corresponding to newname from cache stored in fd contexts of
+     newparent.
+  3. remove entry corresponding to oldparent from cache stored in
+     old-grand-parent, since removing oldname changes st_mtime and st_ctime
+     of oldparent stat.
+  4. remove entry corresponding to newparent from cache stored in
+     new-grand-parent, since adding newname changes st_mtime and st_ctime
+     of newparent stat.
+  5. if oldname happens to be a directory, remove entire cache from all fds
+     opened on it.
+
+* create/mknod/mkdir/symlink/link
+  delete entry corresponding to basename of parent directory in which these
+  operations are happening, from cache stored in context of fds opened on
+  grand-parent, since adding a new entry to a directory changes st_mtime
+  and st_ctime of parent directory.
+
+* setxattr/removexattr
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since setxattr changes st_ctime of file.
+
+* setdents
+  1. remove entry corresponding to basename of path on which fd is opened from
+     cache stored in context of fds opened on parent.
+  2. for each of the entry in the direntry list, delete from cache stored in
+     context of fd, the entry corresponding to basename of path being passed.
+
+* getdents
+  1. remove entry corresponding to basename of path on which fd is opened from
+     cache stored in parent, since getdents changes st_atime.
+  2. remove entries corresponding to symbolic links from cache, since readlink
+     would've changed st_atime.
+
+* checksum
+  delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since st_atime is changed during this call.
+
+* xattrop/fxattrop
+  delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since these calls modify st_ctime of file.
+
+callbacks to be implemented:
+============================
+* releasedir
+  free the context stored in fd.
+
+* forget
+  dree the stat if the inode corresponds to a directory.
+
+limitations:
+============
+* since a readdir does not return extended attributes of file, if need_xattr is
+  set, short-cutting of lookup does not happen and lookup is passed to
+  underlying translators.
+
+* posix_readdir does not check whether the dentries are spanning across multiple
+  mount points. Hence it is not transforming inode numbers in stat buffers if
+  posix is configured to allow export directory spanning on multiple mountpoints.
+  This is a bug which needs to be fixed. posix_readdir should treat dentries the
+  same way as if lookup is happening on dentries.