exofs: BUG: Avoid sbi realloc

Since the beginning we realloced the sbi structure when a bigger
then one device table was specified. (I know that was really stupid).

Then much later when "register bdi" was added (By Jens) it was
registering the pointer to sbi->bdi before the realloc.

We never saw this problem because up till now the realloc did not
do anything since the device table was small enough to fit in the
original allocation. But once we starting testing with large device
tables (Bigger then 28) we noticed the crash of writeback operating
on a deallocated pointer.

* Avoid the all mess by allocating the device-table as a second array
  and get rid of the variable-sized structure and the rest of this
  mess.
* Take the chance to clean near by structures and comments.
* Add a needed dprint on startup to indicate the loaded layout.
* Also move the bdi registration to the very end because it will
  only fail in a low memory, which will probably fail before hand.
  There are many more likely causes to not load before that. This
  way the error handling is made simpler. (Just doing this would be
  enough to fix the BUG)

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

1 files changed, 3 insertions, 6 deletions

diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index e103dbd86fe1..9f62349a5a5c 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -66,13 +66,14 @@ struct exofs_layout {
         enum exofs_inode_layout_gen_functions lay_func;
 
         unsigned        s_numdevs;              /* Num of devices in array    */
-        struct osd_dev  *s_ods[0];              /* Variable length            */
+        struct osd_dev  **s_ods;                /* osd_dev array              */
 };
 
 /*
  * our extension to the in-memory superblock
  */
 struct exofs_sb_info {
+        struct backing_dev_info bdi;            /* register our bdi with VFS  */
         struct exofs_sb_stats s_ess;            /* Written often, pre-allocate*/
         int             s_timeout;              /* timeout for OSD operations */
         uint64_t        s_nextid;               /* highest object ID used     */
@@ -81,15 +82,11 @@ struct exofs_sb_info {
         u32             s_next_generation;      /* next gen # to use          */
         atomic_t        s_curr_pending;         /* number of pending commands */
         uint8_t         s_cred[OSD_CAP_LEN];    /* credential for the fscb    */
-        struct          backing_dev_info bdi;   /* register our bdi with VFS  */
 
         struct pnfs_osd_data_map data_map;      /* Default raid to use
                                                  * FIXME: Needed ?
                                                  */
-/*      struct exofs_layout     dir_layout;*/   /* Default dir layout */
-        struct exofs_layout     layout;         /* Default files layout,
-                                                 * contains the variable osd_dev
-                                                 * array. Keep last */
+        struct exofs_layout     layout;         /* Default files layout       */
         struct osd_dev  *_min_one_dev[1];       /* Place holder for one dev   */
 };