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, 22 insertions, 58 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 4c611871d7e6..ff38a1df22f7 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -43,33 +43,7 @@
 
 #include "mtdcore.h"
 
-/*
- * backing device capabilities for non-mappable devices (such as NAND flash)
- * - permits private mappings, copies are taken of the data
- */
-static struct backing_dev_info mtd_bdi_unmappable = {
-        .capabilities   = BDI_CAP_MAP_COPY,
-};
-
-/*
- * backing device capabilities for R/O mappable devices (such as ROM)
- * - permits private mappings, copies are taken of the data
- * - permits non-writable shared mappings
- */
-static struct backing_dev_info mtd_bdi_ro_mappable = {
-        .capabilities   = (BDI_CAP_MAP_COPY | BDI_CAP_MAP_DIRECT |
-                           BDI_CAP_EXEC_MAP | BDI_CAP_READ_MAP),
-};
-
-/*
- * backing device capabilities for writable mappable devices (such as RAM)
- * - permits private mappings, copies are taken of the data
- * - permits non-writable shared mappings
- */
-static struct backing_dev_info mtd_bdi_rw_mappable = {
-        .capabilities   = (BDI_CAP_MAP_COPY | BDI_CAP_MAP_DIRECT |
-                           BDI_CAP_EXEC_MAP | BDI_CAP_READ_MAP |
-                           BDI_CAP_WRITE_MAP),
+static struct backing_dev_info mtd_bdi = {
 };
 
 static int mtd_cls_suspend(struct device *dev, pm_message_t state);
@@ -365,6 +339,22 @@ static struct device_type mtd_devtype = {
         .release        = mtd_release,
 };
 
+#ifndef CONFIG_MMU
+unsigned mtd_mmap_capabilities(struct mtd_info *mtd)
+{
+        switch (mtd->type) {
+        case MTD_RAM:
+                return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT | NOMMU_MAP_EXEC |
+                        NOMMU_MAP_READ | NOMMU_MAP_WRITE;
+        case MTD_ROM:
+                return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT | NOMMU_MAP_EXEC |
+                        NOMMU_MAP_READ;
+        default:
+                return NOMMU_MAP_COPY;
+        }
+}
+#endif
+
 /**
  *      add_mtd_device - register an MTD device
  *      @mtd: pointer to new MTD device info structure
@@ -380,19 +370,7 @@ int add_mtd_device(struct mtd_info *mtd)
         struct mtd_notifier *not;
         int i, error;
 
-        if (!mtd->backing_dev_info) {
-                switch (mtd->type) {
-                case MTD_RAM:
-                        mtd->backing_dev_info = &mtd_bdi_rw_mappable;
-                        break;
-                case MTD_ROM:
-                        mtd->backing_dev_info = &mtd_bdi_ro_mappable;
-                        break;
-                default:
-                        mtd->backing_dev_info = &mtd_bdi_unmappable;
-                        break;
-                }
-        }
+        mtd->backing_dev_info = &mtd_bdi;
 
         BUG_ON(mtd->writesize == 0);
         mutex_lock(&mtd_table_mutex);
@@ -1237,17 +1215,9 @@ static int __init init_mtd(void)
         if (ret)
                 goto err_reg;
 
-        ret = mtd_bdi_init(&mtd_bdi_unmappable, "mtd-unmap");
-        if (ret)
-                goto err_bdi1;
-
-        ret = mtd_bdi_init(&mtd_bdi_ro_mappable, "mtd-romap");
-        if (ret)
-                goto err_bdi2;
-
-        ret = mtd_bdi_init(&mtd_bdi_rw_mappable, "mtd-rwmap");
+        ret = mtd_bdi_init(&mtd_bdi, "mtd");
         if (ret)
-                goto err_bdi3;
+                goto err_bdi;
 
         proc_mtd = proc_create("mtd", 0, NULL, &mtd_proc_ops);
 
@@ -1260,11 +1230,7 @@ static int __init init_mtd(void)
 out_procfs:
         if (proc_mtd)
                 remove_proc_entry("mtd", NULL);
-err_bdi3:
-        bdi_destroy(&mtd_bdi_ro_mappable);
-err_bdi2:
-        bdi_destroy(&mtd_bdi_unmappable);
-err_bdi1:
+err_bdi:
         class_unregister(&mtd_class);
 err_reg:
         pr_err("Error registering mtd class or bdi: %d\n", ret);
@@ -1277,9 +1243,7 @@ static void __exit cleanup_mtd(void)
         if (proc_mtd)
                 remove_proc_entry("mtd", NULL);
         class_unregister(&mtd_class);
-        bdi_destroy(&mtd_bdi_unmappable);
-        bdi_destroy(&mtd_bdi_ro_mappable);
-        bdi_destroy(&mtd_bdi_rw_mappable);
+        bdi_destroy(&mtd_bdi);
 }
 
 module_init(init_mtd);