exofs: convert io_state to use pages array instead of bio at input

* inode.c operations are full-pages based, and not actually
  true scatter-gather
* Lets us use more pages at once upto 512 (from 249) in 64 bit
* Brings us much much closer to be able to use exofs's io_state engine
  from objlayout driver. (Once I decide where to put the common code)

After RAID0 patch the outer (input) bio was never used as a bio, but
was simply a page carrier into the raid engine. Even in the simple
mirror/single-dev arrangement pages info was copied into a second bio.
It is now easer to just pass a pages array into the io_state and prepare
bio(s) once.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index 0d8a34b21ae1..acfebd36de83 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -128,7 +128,10 @@ struct exofs_io_state {
         loff_t                  offset;
         unsigned long           length;
         void                    *kern_buff;
-        struct bio              *bio;
+
+        struct page             **pages;
+        unsigned                nr_pages;
+        unsigned                pgbase;
 
         /* Attributes */
         unsigned                in_attr_len;