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| author | David Howells <dhowells@redhat.com> | 2006-09-27 01:50:16 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-27 08:26:14 -0700 |
| commit | 5da6185bca064e35aa73a7c1f27488d2b96434f4 (patch) | |
| tree | b854ad2105e177d4b4ec4bb6a5ac26d41ebe368f /fs/char_dev.c | |
| parent | 0ec76a110f432e98277e464b82ace8dd66571689 (diff) | |
| download | lwn-5da6185bca064e35aa73a7c1f27488d2b96434f4.tar.gz lwn-5da6185bca064e35aa73a7c1f27488d2b96434f4.zip | |
[PATCH] NOMMU: Set BDI capabilities for /dev/mem and /dev/kmem
Set the backing device info capabilities for /dev/mem and /dev/kmem to
permit direct sharing under no-MMU conditions and full mapping capabilities
under MMU conditions. Make the BDI used by these available to all directly
mappable character devices.
Also comment the capabilities for /dev/zero.
[akpm@osdl.org: ifdef reductions]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/char_dev.c')
| -rw-r--r-- | fs/char_dev.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/fs/char_dev.c b/fs/char_dev.c index 3483d3cf8087..0009346d827f 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -19,11 +19,30 @@ #include <linux/kobj_map.h> #include <linux/cdev.h> #include <linux/mutex.h> +#include <linux/backing-dev.h> #ifdef CONFIG_KMOD #include <linux/kmod.h> #endif +/* + * capabilities for /dev/mem, /dev/kmem and similar directly mappable character + * devices + * - permits shared-mmap for read, write and/or exec + * - does not permit private mmap in NOMMU mode (can't do COW) + * - no readahead or I/O queue unplugging required + */ +struct backing_dev_info directly_mappable_cdev_bdi = { + .capabilities = ( +#ifdef CONFIG_MMU + /* permit private copies of the data to be taken */ + BDI_CAP_MAP_COPY | +#endif + /* permit direct mmap, for read, write or exec */ + BDI_CAP_MAP_DIRECT | + BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP), +}; + static struct kobj_map *cdev_map; static DEFINE_MUTEX(chrdevs_lock); @@ -461,3 +480,4 @@ EXPORT_SYMBOL(cdev_del); EXPORT_SYMBOL(cdev_add); EXPORT_SYMBOL(register_chrdev); EXPORT_SYMBOL(unregister_chrdev); +EXPORT_SYMBOL(directly_mappable_cdev_bdi); |