fs: introduce f_op->mmap_capabilities for nommu mmap support

Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.

Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead.  Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device.  It also removes the need for
the mtd_inodefs filesystem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 0 insertions, 10 deletions

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index b9000563b9f4..eacc3aac7327 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -732,8 +732,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
 
         concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
 
-        concat->mtd.backing_dev_info = subdev[0]->backing_dev_info;
-
         concat->subdev[0] = subdev[0];
 
         for (i = 1; i < num_devs; i++) {
@@ -761,14 +759,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
                                     subdev[i]->flags & MTD_WRITEABLE;
                 }
 
-                /* only permit direct mapping if the BDIs are all the same
-                 * - copy-mapping is still permitted
-                 */
-                if (concat->mtd.backing_dev_info !=
-                    subdev[i]->backing_dev_info)
-                        concat->mtd.backing_dev_info =
-                                &default_backing_dev_info;
-
                 concat->mtd.size += subdev[i]->size;
                 concat->mtd.ecc_stats.badblocks +=
                         subdev[i]->ecc_stats.badblocks;