454e2398be
Extend the get_sb() filesystem operation to take an extra argument that
permits the VFS to pass in the target vfsmount that defines the mountpoint.
The filesystem is then required to manually set the superblock and root dentry
pointers. For most filesystems, this should be done with simple_set_mnt()
which will set the superblock pointer and then set the root dentry to the
superblock's s_root (as per the old default behaviour).
The get_sb() op now returns an integer as there's now no need to return the
superblock pointer.
This patch permits a superblock to be implicitly shared amongst several mount
points, such as can be done with NFS to avoid potential inode aliasing. In
such a case, simple_set_mnt() would not be called, and instead the mnt_root
and mnt_sb would be set directly.
The patch also makes the following changes:
(*) the get_sb_*() convenience functions in the core kernel now take a vfsmount
pointer argument and return an integer, so most filesystems have to change
very little.
(*) If one of the convenience function is not used, then get_sb() should
normally call simple_set_mnt() to instantiate the vfsmount. This will
always return 0, and so can be tail-called from get_sb().
(*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the
dcache upon superblock destruction rather than shrink_dcache_anon().
This is required because the superblock may now have multiple trees that
aren't actually bound to s_root, but that still need to be cleaned up. The
currently called functions assume that the whole tree is rooted at s_root,
and that anonymous dentries are not the roots of trees which results in
dentries being left unculled.
However, with the way NFS superblock sharing are currently set to be
implemented, these assumptions are violated: the root of the filesystem is
simply a dummy dentry and inode (the real inode for '/' may well be
inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries
with child trees.
[*] Anonymous until discovered from another tree.
(*) The documentation has been adjusted, including the additional bit of
changing ext2_* into foo_* in the documentation.
[akpm@osdl.org: convert ipath_fs, do other stuff]
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nathan Scott <nathans@sgi.com>
Cc: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
651 lines
15 KiB
C
651 lines
15 KiB
C
/*
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* ROMFS file system, Linux implementation
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*
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* Copyright (C) 1997-1999 Janos Farkas <chexum@shadow.banki.hu>
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*
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* Using parts of the minix filesystem
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* and parts of the affs filesystem additionally
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* Copyright (C) 1993 Ray Burr
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* Copyright (C) 1996 Hans-Joachim Widmaier
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Changes
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* Changed for 2.1.19 modules
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* Jan 1997 Initial release
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* Jun 1997 2.1.43+ changes
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* Proper page locking in readpage
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* Changed to work with 2.1.45+ fs
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* Jul 1997 Fixed follow_link
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* 2.1.47
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* lookup shouldn't return -ENOENT
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* from Horst von Brand:
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* fail on wrong checksum
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* double unlock_super was possible
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* correct namelen for statfs
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* spotted by Bill Hawes:
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* readlink shouldn't iput()
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* Jun 1998 2.1.106 from Avery Pennarun: glibc scandir()
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* exposed a problem in readdir
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* 2.1.107 code-freeze spellchecker run
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* Aug 1998 2.1.118+ VFS changes
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* Sep 1998 2.1.122 another VFS change (follow_link)
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* Apr 1999 2.2.7 no more EBADF checking in
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* lookup/readdir, use ERR_PTR
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* Jun 1999 2.3.6 d_alloc_root use changed
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* 2.3.9 clean up usage of ENOENT/negative
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* dentries in lookup
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* clean up page flags setting
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* (error, uptodate, locking) in
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* in readpage
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* use init_special_inode for
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* fifos/sockets (and streamline) in
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* read_inode, fix _ops table order
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* Aug 1999 2.3.16 __initfunc() => __init change
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* Oct 1999 2.3.24 page->owner hack obsoleted
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* Nov 1999 2.3.27 2.3.25+ page->offset => index change
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*/
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/* todo:
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* - see Documentation/filesystems/romfs.txt
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* - use allocated, not stack memory for file names?
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* - considering write access...
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* - network (tftp) files?
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* - merge back some _op tables
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*/
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/*
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* Sorry about some optimizations and for some goto's. I just wanted
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* to squeeze some more bytes out of this code.. :)
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/slab.h>
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#include <linux/romfs_fs.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/pagemap.h>
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#include <linux/smp_lock.h>
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#include <linux/buffer_head.h>
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#include <linux/vfs.h>
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#include <asm/uaccess.h>
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struct romfs_inode_info {
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unsigned long i_metasize; /* size of non-data area */
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unsigned long i_dataoffset; /* from the start of fs */
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struct inode vfs_inode;
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};
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/* instead of private superblock data */
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static inline unsigned long romfs_maxsize(struct super_block *sb)
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{
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return (unsigned long)sb->s_fs_info;
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}
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static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
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{
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return list_entry(inode, struct romfs_inode_info, vfs_inode);
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}
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static __u32
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romfs_checksum(void *data, int size)
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{
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__u32 sum;
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__be32 *ptr;
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sum = 0; ptr = data;
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size>>=2;
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while (size>0) {
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sum += be32_to_cpu(*ptr++);
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size--;
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}
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return sum;
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}
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static struct super_operations romfs_ops;
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static int romfs_fill_super(struct super_block *s, void *data, int silent)
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{
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struct buffer_head *bh;
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struct romfs_super_block *rsb;
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struct inode *root;
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int sz;
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/* I would parse the options here, but there are none.. :) */
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sb_set_blocksize(s, ROMBSIZE);
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s->s_maxbytes = 0xFFFFFFFF;
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bh = sb_bread(s, 0);
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if (!bh) {
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/* XXX merge with other printk? */
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printk ("romfs: unable to read superblock\n");
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goto outnobh;
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}
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rsb = (struct romfs_super_block *)bh->b_data;
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sz = be32_to_cpu(rsb->size);
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if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
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|| sz < ROMFH_SIZE) {
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if (!silent)
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printk ("VFS: Can't find a romfs filesystem on dev "
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"%s.\n", s->s_id);
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goto out;
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}
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if (romfs_checksum(rsb, min_t(int, sz, 512))) {
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printk ("romfs: bad initial checksum on dev "
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"%s.\n", s->s_id);
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goto out;
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}
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s->s_magic = ROMFS_MAGIC;
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s->s_fs_info = (void *)(long)sz;
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s->s_flags |= MS_RDONLY;
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/* Find the start of the fs */
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sz = (ROMFH_SIZE +
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strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
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& ROMFH_MASK;
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s->s_op = &romfs_ops;
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root = iget(s, sz);
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if (!root)
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goto out;
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s->s_root = d_alloc_root(root);
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if (!s->s_root)
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goto outiput;
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brelse(bh);
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return 0;
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outiput:
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iput(root);
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out:
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brelse(bh);
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outnobh:
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return -EINVAL;
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}
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/* That's simple too. */
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static int
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romfs_statfs(struct super_block *sb, struct kstatfs *buf)
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{
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buf->f_type = ROMFS_MAGIC;
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buf->f_bsize = ROMBSIZE;
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buf->f_bfree = buf->f_bavail = buf->f_ffree;
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buf->f_blocks = (romfs_maxsize(sb)+ROMBSIZE-1)>>ROMBSBITS;
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buf->f_namelen = ROMFS_MAXFN;
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return 0;
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}
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/* some helper routines */
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static int
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romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
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{
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struct buffer_head *bh;
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unsigned long avail, maxsize, res;
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maxsize = romfs_maxsize(i->i_sb);
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if (offset >= maxsize)
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return -1;
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/* strnlen is almost always valid */
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if (count > maxsize || offset+count > maxsize)
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count = maxsize-offset;
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bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
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if (!bh)
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return -1; /* error */
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avail = ROMBSIZE - (offset & ROMBMASK);
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maxsize = min_t(unsigned long, count, avail);
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res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
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brelse(bh);
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if (res < maxsize)
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return res; /* found all of it */
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while (res < count) {
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offset += maxsize;
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bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
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if (!bh)
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return -1;
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maxsize = min_t(unsigned long, count - res, ROMBSIZE);
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avail = strnlen(bh->b_data, maxsize);
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res += avail;
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brelse(bh);
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if (avail < maxsize)
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return res;
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}
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return res;
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}
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static int
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romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
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{
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struct buffer_head *bh;
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unsigned long avail, maxsize, res;
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maxsize = romfs_maxsize(i->i_sb);
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if (offset >= maxsize || count > maxsize || offset+count>maxsize)
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return -1;
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bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
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if (!bh)
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return -1; /* error */
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avail = ROMBSIZE - (offset & ROMBMASK);
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maxsize = min_t(unsigned long, count, avail);
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memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
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brelse(bh);
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res = maxsize; /* all of it */
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while (res < count) {
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offset += maxsize;
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dest += maxsize;
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bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
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if (!bh)
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return -1;
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maxsize = min_t(unsigned long, count - res, ROMBSIZE);
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memcpy(dest, bh->b_data, maxsize);
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brelse(bh);
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res += maxsize;
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}
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return res;
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}
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static unsigned char romfs_dtype_table[] = {
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DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
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};
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static int
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romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
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{
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struct inode *i = filp->f_dentry->d_inode;
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struct romfs_inode ri;
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unsigned long offset, maxoff;
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int j, ino, nextfh;
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int stored = 0;
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char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
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lock_kernel();
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maxoff = romfs_maxsize(i->i_sb);
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offset = filp->f_pos;
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if (!offset) {
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offset = i->i_ino & ROMFH_MASK;
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if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
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goto out;
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offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
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}
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/* Not really failsafe, but we are read-only... */
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for(;;) {
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if (!offset || offset >= maxoff) {
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offset = maxoff;
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filp->f_pos = offset;
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goto out;
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}
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filp->f_pos = offset;
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/* Fetch inode info */
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if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
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goto out;
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j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
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if (j < 0)
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goto out;
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fsname[j]=0;
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romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
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ino = offset;
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nextfh = be32_to_cpu(ri.next);
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if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
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ino = be32_to_cpu(ri.spec);
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if (filldir(dirent, fsname, j, offset, ino,
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romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
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goto out;
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}
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stored++;
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offset = nextfh & ROMFH_MASK;
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}
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out:
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unlock_kernel();
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return stored;
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}
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static struct dentry *
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romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
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{
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unsigned long offset, maxoff;
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int fslen, res;
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struct inode *inode;
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char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
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struct romfs_inode ri;
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const char *name; /* got from dentry */
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int len;
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res = -EACCES; /* placeholder for "no data here" */
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offset = dir->i_ino & ROMFH_MASK;
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lock_kernel();
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if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
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goto out;
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maxoff = romfs_maxsize(dir->i_sb);
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offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
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/* OK, now find the file whose name is in "dentry" in the
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* directory specified by "dir". */
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name = dentry->d_name.name;
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len = dentry->d_name.len;
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for(;;) {
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if (!offset || offset >= maxoff)
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goto out0;
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if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
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goto out;
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/* try to match the first 16 bytes of name */
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fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
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if (len < ROMFH_SIZE) {
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if (len == fslen) {
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/* both are shorter, and same size */
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romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
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if (strncmp (name, fsname, len) == 0)
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break;
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}
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} else if (fslen >= ROMFH_SIZE) {
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/* both are longer; XXX optimize max size */
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fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
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if (len == fslen) {
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romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
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if (strncmp(name, fsname, len) == 0)
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break;
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}
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}
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/* next entry */
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offset = be32_to_cpu(ri.next) & ROMFH_MASK;
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}
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/* Hard link handling */
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if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
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offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
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if ((inode = iget(dir->i_sb, offset)))
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goto outi;
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/*
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* it's a bit funky, _lookup needs to return an error code
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* (negative) or a NULL, both as a dentry. ENOENT should not
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* be returned, instead we need to create a negative dentry by
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* d_add(dentry, NULL); and return 0 as no error.
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* (Although as I see, it only matters on writable file
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* systems).
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*/
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out0: inode = NULL;
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outi: res = 0;
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d_add (dentry, inode);
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out: unlock_kernel();
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return ERR_PTR(res);
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}
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/*
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* Ok, we do readpage, to be able to execute programs. Unfortunately,
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* we can't use bmap, since we may have looser alignments.
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*/
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static int
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romfs_readpage(struct file *file, struct page * page)
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{
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struct inode *inode = page->mapping->host;
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loff_t offset, avail, readlen;
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void *buf;
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int result = -EIO;
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page_cache_get(page);
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lock_kernel();
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buf = kmap(page);
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if (!buf)
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goto err_out;
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/* 32 bit warning -- but not for us :) */
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offset = page_offset(page);
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if (offset < i_size_read(inode)) {
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avail = inode->i_size-offset;
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readlen = min_t(unsigned long, avail, PAGE_SIZE);
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if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
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if (readlen < PAGE_SIZE) {
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memset(buf + readlen,0,PAGE_SIZE-readlen);
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}
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SetPageUptodate(page);
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result = 0;
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}
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}
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if (result) {
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memset(buf, 0, PAGE_SIZE);
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SetPageError(page);
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}
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flush_dcache_page(page);
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unlock_page(page);
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kunmap(page);
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err_out:
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page_cache_release(page);
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unlock_kernel();
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return result;
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}
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/* Mapping from our types to the kernel */
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static struct address_space_operations romfs_aops = {
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.readpage = romfs_readpage
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};
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static const struct file_operations romfs_dir_operations = {
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.read = generic_read_dir,
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.readdir = romfs_readdir,
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};
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|
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static struct inode_operations romfs_dir_inode_operations = {
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.lookup = romfs_lookup,
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};
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static mode_t romfs_modemap[] =
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{
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0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
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S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
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};
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|
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static void
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romfs_read_inode(struct inode *i)
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{
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|
int nextfh, ino;
|
|
struct romfs_inode ri;
|
|
|
|
ino = i->i_ino & ROMFH_MASK;
|
|
i->i_mode = 0;
|
|
|
|
/* Loop for finding the real hard link */
|
|
for(;;) {
|
|
if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
|
|
printk("romfs: read error for inode 0x%x\n", ino);
|
|
return;
|
|
}
|
|
/* XXX: do romfs_checksum here too (with name) */
|
|
|
|
nextfh = be32_to_cpu(ri.next);
|
|
if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
|
|
break;
|
|
|
|
ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
|
|
}
|
|
|
|
i->i_nlink = 1; /* Hard to decide.. */
|
|
i->i_size = be32_to_cpu(ri.size);
|
|
i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
|
|
i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
|
|
i->i_uid = i->i_gid = 0;
|
|
|
|
/* Precalculate the data offset */
|
|
ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
|
|
if (ino >= 0)
|
|
ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
|
|
else
|
|
ino = 0;
|
|
|
|
ROMFS_I(i)->i_metasize = ino;
|
|
ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
|
|
|
|
/* Compute permissions */
|
|
ino = romfs_modemap[nextfh & ROMFH_TYPE];
|
|
/* only "normal" files have ops */
|
|
switch (nextfh & ROMFH_TYPE) {
|
|
case 1:
|
|
i->i_size = ROMFS_I(i)->i_metasize;
|
|
i->i_op = &romfs_dir_inode_operations;
|
|
i->i_fop = &romfs_dir_operations;
|
|
if (nextfh & ROMFH_EXEC)
|
|
ino |= S_IXUGO;
|
|
i->i_mode = ino;
|
|
break;
|
|
case 2:
|
|
i->i_fop = &generic_ro_fops;
|
|
i->i_data.a_ops = &romfs_aops;
|
|
if (nextfh & ROMFH_EXEC)
|
|
ino |= S_IXUGO;
|
|
i->i_mode = ino;
|
|
break;
|
|
case 3:
|
|
i->i_op = &page_symlink_inode_operations;
|
|
i->i_data.a_ops = &romfs_aops;
|
|
i->i_mode = ino | S_IRWXUGO;
|
|
break;
|
|
default:
|
|
/* depending on MBZ for sock/fifos */
|
|
nextfh = be32_to_cpu(ri.spec);
|
|
init_special_inode(i, ino,
|
|
MKDEV(nextfh>>16,nextfh&0xffff));
|
|
}
|
|
}
|
|
|
|
static kmem_cache_t * romfs_inode_cachep;
|
|
|
|
static struct inode *romfs_alloc_inode(struct super_block *sb)
|
|
{
|
|
struct romfs_inode_info *ei;
|
|
ei = (struct romfs_inode_info *)kmem_cache_alloc(romfs_inode_cachep, SLAB_KERNEL);
|
|
if (!ei)
|
|
return NULL;
|
|
return &ei->vfs_inode;
|
|
}
|
|
|
|
static void romfs_destroy_inode(struct inode *inode)
|
|
{
|
|
kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
|
|
}
|
|
|
|
static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
|
|
{
|
|
struct romfs_inode_info *ei = (struct romfs_inode_info *) foo;
|
|
|
|
if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
|
|
SLAB_CTOR_CONSTRUCTOR)
|
|
inode_init_once(&ei->vfs_inode);
|
|
}
|
|
|
|
static int init_inodecache(void)
|
|
{
|
|
romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
|
|
sizeof(struct romfs_inode_info),
|
|
0, (SLAB_RECLAIM_ACCOUNT|
|
|
SLAB_MEM_SPREAD),
|
|
init_once, NULL);
|
|
if (romfs_inode_cachep == NULL)
|
|
return -ENOMEM;
|
|
return 0;
|
|
}
|
|
|
|
static void destroy_inodecache(void)
|
|
{
|
|
if (kmem_cache_destroy(romfs_inode_cachep))
|
|
printk(KERN_INFO "romfs_inode_cache: not all structures were freed\n");
|
|
}
|
|
|
|
static int romfs_remount(struct super_block *sb, int *flags, char *data)
|
|
{
|
|
*flags |= MS_RDONLY;
|
|
return 0;
|
|
}
|
|
|
|
static struct super_operations romfs_ops = {
|
|
.alloc_inode = romfs_alloc_inode,
|
|
.destroy_inode = romfs_destroy_inode,
|
|
.read_inode = romfs_read_inode,
|
|
.statfs = romfs_statfs,
|
|
.remount_fs = romfs_remount,
|
|
};
|
|
|
|
static int romfs_get_sb(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
|
|
{
|
|
return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
|
|
mnt);
|
|
}
|
|
|
|
static struct file_system_type romfs_fs_type = {
|
|
.owner = THIS_MODULE,
|
|
.name = "romfs",
|
|
.get_sb = romfs_get_sb,
|
|
.kill_sb = kill_block_super,
|
|
.fs_flags = FS_REQUIRES_DEV,
|
|
};
|
|
|
|
static int __init init_romfs_fs(void)
|
|
{
|
|
int err = init_inodecache();
|
|
if (err)
|
|
goto out1;
|
|
err = register_filesystem(&romfs_fs_type);
|
|
if (err)
|
|
goto out;
|
|
return 0;
|
|
out:
|
|
destroy_inodecache();
|
|
out1:
|
|
return err;
|
|
}
|
|
|
|
static void __exit exit_romfs_fs(void)
|
|
{
|
|
unregister_filesystem(&romfs_fs_type);
|
|
destroy_inodecache();
|
|
}
|
|
|
|
/* Yes, works even as a module... :) */
|
|
|
|
module_init(init_romfs_fs)
|
|
module_exit(exit_romfs_fs)
|
|
MODULE_LICENSE("GPL");
|