4b19de6d1c
The previous patch db203d53d4 ("mm:
tiny-shmem fix lock ordering: mmap_sem vs i_mutex") to fix the lock
ordering in tiny-shmem breaks shared anonymous and IPC memory on NOMMU
architectures because it was using the expanding truncate to signal ramfs
to allocate a physically contiguous RAM backing the inode (otherwise it is
unusable for "memory mapping" it to userspace).
However do_truncate is what caused the lock ordering error, due to it
taking i_mutex. In this case, we can actually just call ramfs directly to
allocate memory for the mapping, rather than go via truncate.
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
133 lines
2.9 KiB
C
133 lines
2.9 KiB
C
/*
|
|
* tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
|
|
*
|
|
* Matt Mackall <mpm@selenic.com> January, 2004
|
|
* derived from mm/shmem.c and fs/ramfs/inode.c
|
|
*
|
|
* This is intended for small system where the benefits of the full
|
|
* shmem code (swap-backed and resource-limited) are outweighed by
|
|
* their complexity. On systems without swap this code should be
|
|
* effectively equivalent, but much lighter weight.
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/init.h>
|
|
#include <linux/vfs.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/file.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/module.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/ramfs.h>
|
|
|
|
static struct file_system_type tmpfs_fs_type = {
|
|
.name = "tmpfs",
|
|
.get_sb = ramfs_get_sb,
|
|
.kill_sb = kill_litter_super,
|
|
};
|
|
|
|
static struct vfsmount *shm_mnt;
|
|
|
|
static int __init init_tmpfs(void)
|
|
{
|
|
BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
|
|
|
|
shm_mnt = kern_mount(&tmpfs_fs_type);
|
|
BUG_ON(IS_ERR(shm_mnt));
|
|
|
|
return 0;
|
|
}
|
|
module_init(init_tmpfs)
|
|
|
|
/**
|
|
* shmem_file_setup - get an unlinked file living in tmpfs
|
|
* @name: name for dentry (to be seen in /proc/<pid>/maps
|
|
* @size: size to be set for the file
|
|
* @flags: vm_flags
|
|
*/
|
|
struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
|
|
{
|
|
int error;
|
|
struct file *file;
|
|
struct inode *inode;
|
|
struct dentry *dentry, *root;
|
|
struct qstr this;
|
|
|
|
if (IS_ERR(shm_mnt))
|
|
return (void *)shm_mnt;
|
|
|
|
error = -ENOMEM;
|
|
this.name = name;
|
|
this.len = strlen(name);
|
|
this.hash = 0; /* will go */
|
|
root = shm_mnt->mnt_root;
|
|
dentry = d_alloc(root, &this);
|
|
if (!dentry)
|
|
goto put_memory;
|
|
|
|
error = -ENFILE;
|
|
file = get_empty_filp();
|
|
if (!file)
|
|
goto put_dentry;
|
|
|
|
error = -ENOSPC;
|
|
inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
|
|
if (!inode)
|
|
goto close_file;
|
|
|
|
d_instantiate(dentry, inode);
|
|
inode->i_size = size;
|
|
inode->i_nlink = 0; /* It is unlinked */
|
|
init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
|
|
&ramfs_file_operations);
|
|
|
|
#ifndef CONFIG_MMU
|
|
error = ramfs_nommu_expand_for_mapping(inode, size);
|
|
if (error)
|
|
goto close_file;
|
|
#endif
|
|
return file;
|
|
|
|
close_file:
|
|
put_filp(file);
|
|
put_dentry:
|
|
dput(dentry);
|
|
put_memory:
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
/**
|
|
* shmem_zero_setup - setup a shared anonymous mapping
|
|
* @vma: the vma to be mmapped is prepared by do_mmap_pgoff
|
|
*/
|
|
int shmem_zero_setup(struct vm_area_struct *vma)
|
|
{
|
|
struct file *file;
|
|
loff_t size = vma->vm_end - vma->vm_start;
|
|
|
|
file = shmem_file_setup("dev/zero", size, vma->vm_flags);
|
|
if (IS_ERR(file))
|
|
return PTR_ERR(file);
|
|
|
|
if (vma->vm_file)
|
|
fput(vma->vm_file);
|
|
vma->vm_file = file;
|
|
vma->vm_ops = &generic_file_vm_ops;
|
|
return 0;
|
|
}
|
|
|
|
int shmem_unuse(swp_entry_t entry, struct page *page)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
#ifndef CONFIG_MMU
|
|
unsigned long shmem_get_unmapped_area(struct file *file,
|
|
unsigned long addr,
|
|
unsigned long len,
|
|
unsigned long pgoff,
|
|
unsigned long flags)
|
|
{
|
|
return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
|
|
}
|
|
#endif
|