From 642fb4d1f1dd2417aa69189fe5ceb81e4fb72900 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 6 Jan 2006 00:11:41 -0800 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ramfs/inode.c | 22 +--------------------- 1 file changed, 1 insertion(+), 21 deletions(-) (limited to 'fs/ramfs/inode.c') 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 @@ #include #include +#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 @@ static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * 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, -- cgit v1.2.3-58-ga151