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authorDavid Howells <dhowells@redhat.com>2006-01-06 03:11:41 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-06 11:33:32 -0500
commit642fb4d1f1dd2417aa69189fe5ceb81e4fb72900 (patch)
tree77427e3141a6160bfa09ed3af4428c6e874f3e0c /fs/ramfs/inode.c
parent9f6d4b0c21a6894dad7665d3dda4174c7c120784 (diff)
[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>
Diffstat (limited to 'fs/ramfs/inode.c')
-rw-r--r--fs/ramfs/inode.c22
1 files changed, 1 insertions, 21 deletions
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 0a88917605ae..c66bd5e4c05c 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -34,13 +34,12 @@
34#include <linux/ramfs.h> 34#include <linux/ramfs.h>
35 35
36#include <asm/uaccess.h> 36#include <asm/uaccess.h>
37#include "internal.h"
37 38
38/* some random number */ 39/* some random number */
39#define RAMFS_MAGIC 0x858458f6 40#define RAMFS_MAGIC 0x858458f6
40 41
41static struct super_operations ramfs_ops; 42static struct super_operations ramfs_ops;
42static struct address_space_operations ramfs_aops;
43static struct inode_operations ramfs_file_inode_operations;
44static struct inode_operations ramfs_dir_inode_operations; 43static struct inode_operations ramfs_dir_inode_operations;
45 44
46static struct backing_dev_info ramfs_backing_dev_info = { 45static struct backing_dev_info ramfs_backing_dev_info = {
@@ -142,25 +141,6 @@ static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char *
142 return error; 141 return error;
143} 142}
144 143
145static struct address_space_operations ramfs_aops = {
146 .readpage = simple_readpage,
147 .prepare_write = simple_prepare_write,
148 .commit_write = simple_commit_write
149};
150
151struct file_operations ramfs_file_operations = {
152 .read = generic_file_read,
153 .write = generic_file_write,
154 .mmap = generic_file_mmap,
155 .fsync = simple_sync_file,
156 .sendfile = generic_file_sendfile,
157 .llseek = generic_file_llseek,
158};
159
160static struct inode_operations ramfs_file_inode_operations = {
161 .getattr = simple_getattr,
162};
163
164static struct inode_operations ramfs_dir_inode_operations = { 144static struct inode_operations ramfs_dir_inode_operations = {
165 .create = ramfs_create, 145 .create = ramfs_create,
166 .lookup = simple_lookup, 146 .lookup = simple_lookup,