[PATCH] NOMMU: Provide shared-writable mmap support on ramfs
The attached patch makes ramfs support shared-writable mmaps by:
(1) Attempting to perform a contiguous block allocation to the requested size
when truncate attempts to increase the file from zero size, such as
happens when:
fd = shm_open("/file/on/ramfs", ...):
ftruncate(fd, size_requested);
addr = mmap(NULL, subsize, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED,
fd, offset);
(2) Permitting any shared-writable mapping over any contiguous set of extant
pages. get_unmapped_area() will return the address into the actual ramfs
pages. The mapping may start anywhere and be of any size, but may not go
over the end of file. Multiple mappings may overlap in any way.
(3) Not permitting a file to be shrunk if it would truncate any shared
mappings (private mappings are copied).
Thus this patch provides support for POSIX shared memory on NOMMU kernels,
with certain limitations such as there being a large enough block of pages
available to support the allocation and it only working on directly mappable
filesystems.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 0a88917..c66bd5e 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -34,13 +34,12 @@
#include <linux/ramfs.h>
#include <asm/uaccess.h>
+#include "internal.h"
/* some random number */
#define RAMFS_MAGIC 0x858458f6
static struct super_operations ramfs_ops;
-static struct address_space_operations ramfs_aops;
-static struct inode_operations ramfs_file_inode_operations;
static struct inode_operations ramfs_dir_inode_operations;
static struct backing_dev_info ramfs_backing_dev_info = {
@@ -142,25 +141,6 @@
return error;
}
-static struct address_space_operations ramfs_aops = {
- .readpage = simple_readpage,
- .prepare_write = simple_prepare_write,
- .commit_write = simple_commit_write
-};
-
-struct file_operations ramfs_file_operations = {
- .read = generic_file_read,
- .write = generic_file_write,
- .mmap = generic_file_mmap,
- .fsync = simple_sync_file,
- .sendfile = generic_file_sendfile,
- .llseek = generic_file_llseek,
-};
-
-static struct inode_operations ramfs_file_inode_operations = {
- .getattr = simple_getattr,
-};
-
static struct inode_operations ramfs_dir_inode_operations = {
.create = ramfs_create,
.lookup = simple_lookup,
