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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
/*
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* tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
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*
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* Matt Mackall <mpm@selenic.com> January, 2004
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* derived from mm/shmem.c and fs/ramfs/inode.c
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*
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* This is intended for small system where the benefits of the full
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* shmem code (swap-backed and resource-limited) are outweighed by
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* their complexity. On systems without swap this code should be
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* effectively equivalent, but much lighter weight.
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*/
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/vfs.h>
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#include <linux/mount.h>
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/swap.h>
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#include <linux/ramfs.h>
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static struct file_system_type tmpfs_fs_type = {
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.name = "tmpfs",
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.get_sb = ramfs_get_sb,
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.kill_sb = kill_litter_super,
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};
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static struct vfsmount *shm_mnt;
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static int __init init_tmpfs(void)
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{
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BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
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shm_mnt = kern_mount(&tmpfs_fs_type);
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BUG_ON(IS_ERR(shm_mnt));
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return 0;
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}
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module_init(init_tmpfs)
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/**
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* shmem_file_setup - get an unlinked file living in tmpfs
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* @name: name for dentry (to be seen in /proc/<pid>/maps
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* @size: size to be set for the file
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* @flags: vm_flags
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*/
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struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
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{
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int error;
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struct file *file;
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struct inode *inode;
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struct dentry *dentry, *root;
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struct qstr this;
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if (IS_ERR(shm_mnt))
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return (void *)shm_mnt;
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error = -ENOMEM;
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this.name = name;
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this.len = strlen(name);
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this.hash = 0; /* will go */
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root = shm_mnt->mnt_root;
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dentry = d_alloc(root, &this);
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if (!dentry)
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goto put_memory;
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error = -ENFILE;
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file = get_empty_filp();
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if (!file)
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goto put_dentry;
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error = -ENOSPC;
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inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
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if (!inode)
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goto close_file;
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d_instantiate(dentry, inode);
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inode->i_size = size;
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inode->i_nlink = 0; /* It is unlinked */
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init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
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&ramfs_file_operations);
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#ifndef CONFIG_MMU
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error = ramfs_nommu_expand_for_mapping(inode, size);
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if (error)
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goto close_file;
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#endif
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return file;
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close_file:
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put_filp(file);
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put_dentry:
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dput(dentry);
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put_memory:
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return ERR_PTR(error);
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}
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/**
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* shmem_zero_setup - setup a shared anonymous mapping
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* @vma: the vma to be mmapped is prepared by do_mmap_pgoff
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*/
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int shmem_zero_setup(struct vm_area_struct *vma)
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{
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struct file *file;
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loff_t size = vma->vm_end - vma->vm_start;
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file = shmem_file_setup("dev/zero", size, vma->vm_flags);
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if (IS_ERR(file))
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return PTR_ERR(file);
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if (vma->vm_file)
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fput(vma->vm_file);
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vma->vm_file = file;
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vma->vm_ops = &generic_file_vm_ops;
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return 0;
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}
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int shmem_unuse(swp_entry_t entry, struct page *page)
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{
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return 0;
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}
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#ifndef CONFIG_MMU
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unsigned long shmem_get_unmapped_area(struct file *file,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags)
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{
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return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
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}
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#endif
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