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linux/fs/9p/v9fs.h
Dominique Martinet be2ca38253 Revert "fs/9p: simplify iget to remove unnecessary paths" 
This reverts commit 724a08450f.

This code simplification introduced significant regressions on servers
that do not remap inode numbers when exporting multiple underlying
filesystems with colliding inodes, as can be illustrated with simple
tmpfs exports in qemu with remapping disabled:
```
# host side
cd /tmp/linux-test
mkdir m1 m2
mount -t tmpfs tmpfs m1
mount -t tmpfs tmpfs m2
mkdir m1/dir m2/dir
echo foo > m1/dir/foo
echo bar > m2/dir/bar

# guest side
# started with -virtfs local,path=/tmp/linux-test,mount_tag=tmp,security_model=mapped-file
mount -t 9p -o trans=virtio,debug=1 tmp /mnt/t

ls /mnt/t/m1/dir
# foo
ls /mnt/t/m2/dir
# bar (works ok if directry isn't open)

# cd to keep first dir's inode alive
cd /mnt/t/m1/dir
ls /mnt/t/m2/dir
# foo (should be bar)
```
Other examples can be crafted with regular files with fscache enabled,
in which case I/Os just happen to the wrong file leading to
corruptions, or guest failing to boot with:
  | VFS: Lookup of 'com.android.runtime' in 9p 9p would have caused loop

In theory, we'd want the servers to be smart enough and ensure they
never send us two different files with the same 'qid.path', but while
qemu has an option to remap that is recommended (and qemu prints a
warning if this case happens), there are many other servers which do
not (kvmtool, nfs-ganesha, probably diod...), we should at least ensure
we don't cause regressions on this:
- assume servers can't be trusted and operations that should get a 'new'
inode properly do so. commit d05dcfdf5e (" fs/9p: mitigate inode
collisions") attempted to do this, but v9fs_fid_iget_dotl() was not
called so some higher level of caching got in the way; this needs to be
fixed properly before we can re-apply the patches.
- if we ever want to really simplify this code, we will need to add some
negotiation with the server at mount time where the server could claim
they handle this properly, at which point we could optimize this out.
(but that might not be needed at all if we properly handle the 'new'
check?)

Fixes: 724a08450f ("fs/9p: simplify iget to remove unnecessary paths")
Reported-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/all/20240408141436.GA17022@redhat.com/
Link: https://lkml.kernel.org/r/20240923100508.GA32066@willie-the-truck
Cc: stable@vger.kernel.org # v6.9+
Message-ID: <20241024-revert_iget-v1-4-4cac63d25f72@codewreck.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
2024-10-25 06:26:09 +09:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* V9FS definitions.
*
* Copyright (C) 2004-2008 by Eric Van Hensbergen <ericvh@gmail.com>
* Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
*/
#ifndef FS_9P_V9FS_H
#define FS_9P_V9FS_H
#include <linux/backing-dev.h>
#include <linux/netfs.h>
/**
* enum p9_session_flags - option flags for each 9P session
* @V9FS_PROTO_2000U: whether or not to use 9P2000.u extensions
* @V9FS_PROTO_2000L: whether or not to use 9P2000.l extensions
* @V9FS_ACCESS_SINGLE: only the mounting user can access the hierarchy
* @V9FS_ACCESS_USER: a new attach will be issued for every user (default)
* @V9FS_ACCESS_CLIENT: Just like user, but access check is performed on client.
* @V9FS_ACCESS_ANY: use a single attach for all users
* @V9FS_ACCESS_MASK: bit mask of different ACCESS options
* @V9FS_POSIX_ACL: POSIX ACLs are enforced
*
* Session flags reflect options selected by users at mount time
*/
#define V9FS_ACCESS_ANY (V9FS_ACCESS_SINGLE | \
V9FS_ACCESS_USER | \
V9FS_ACCESS_CLIENT)
#define V9FS_ACCESS_MASK V9FS_ACCESS_ANY
#define V9FS_ACL_MASK V9FS_POSIX_ACL
enum p9_session_flags {
V9FS_PROTO_2000U = 0x01,
V9FS_PROTO_2000L = 0x02,
V9FS_ACCESS_SINGLE = 0x04,
V9FS_ACCESS_USER = 0x08,
V9FS_ACCESS_CLIENT = 0x10,
V9FS_POSIX_ACL = 0x20,
V9FS_NO_XATTR = 0x40,
V9FS_IGNORE_QV = 0x80, /* ignore qid.version for cache hints */
V9FS_DIRECT_IO = 0x100,
V9FS_SYNC = 0x200
};
/**
* enum p9_cache_shortcuts - human readable cache preferences
* @CACHE_SC_NONE: disable all caches
* @CACHE_SC_READAHEAD: only provide caching for readahead
* @CACHE_SC_MMAP: provide caching to enable mmap
* @CACHE_SC_LOOSE: non-coherent caching for files and meta data
* @CACHE_SC_FSCACHE: persistent non-coherent caching for files and meta-data
*
*/
enum p9_cache_shortcuts {
CACHE_SC_NONE = 0b00000000,
CACHE_SC_READAHEAD = 0b00000001,
CACHE_SC_MMAP = 0b00000101,
CACHE_SC_LOOSE = 0b00001111,
CACHE_SC_FSCACHE = 0b10001111,
};
/**
* enum p9_cache_bits - possible values of ->cache
* @CACHE_NONE: caches disabled
* @CACHE_FILE: file caching (open to close)
* @CACHE_META: meta-data and directory caching
* @CACHE_WRITEBACK: write-back caching for files
* @CACHE_LOOSE: don't check cache consistency
* @CACHE_FSCACHE: local persistent caches
*
*/
enum p9_cache_bits {
CACHE_NONE = 0b00000000,
CACHE_FILE = 0b00000001,
CACHE_META = 0b00000010,
CACHE_WRITEBACK = 0b00000100,
CACHE_LOOSE = 0b00001000,
CACHE_FSCACHE = 0b10000000,
};
/**
* struct v9fs_session_info - per-instance session information
* @flags: session options of type &p9_session_flags
* @nodev: set to 1 to disable device mapping
* @debug: debug level
* @afid: authentication handle
* @cache: cache mode of type &p9_cache_bits
* @cachetag: the tag of the cache associated with this session
* @fscache: session cookie associated with FS-Cache
* @uname: string user name to mount hierarchy as
* @aname: mount specifier for remote hierarchy
* @maxdata: maximum data to be sent/recvd per protocol message
* @dfltuid: default numeric userid to mount hierarchy as
* @dfltgid: default numeric groupid to mount hierarchy as
* @uid: if %V9FS_ACCESS_SINGLE, the numeric uid which mounted the hierarchy
* @clnt: reference to 9P network client instantiated for this session
* @slist: reference to list of registered 9p sessions
*
* This structure holds state for each session instance established during
* a sys_mount() .
*
* Bugs: there seems to be a lot of state which could be condensed and/or
* removed.
*/
struct v9fs_session_info {
/* options */
unsigned int flags;
unsigned char nodev;
unsigned short debug;
unsigned int afid;
unsigned int cache;
#ifdef CONFIG_9P_FSCACHE
char *cachetag;
struct fscache_volume *fscache;
#endif
char *uname; /* user name to mount as */
char *aname; /* name of remote hierarchy being mounted */
unsigned int maxdata; /* max data for client interface */
kuid_t dfltuid; /* default uid/muid for legacy support */
kgid_t dfltgid; /* default gid for legacy support */
kuid_t uid; /* if ACCESS_SINGLE, the uid that has access */
struct p9_client *clnt; /* 9p client */
struct list_head slist; /* list of sessions registered with v9fs */
struct rw_semaphore rename_sem;
long session_lock_timeout; /* retry interval for blocking locks */
};
/* cache_validity flags */
#define V9FS_INO_INVALID_ATTR 0x01
struct v9fs_inode {
struct netfs_inode netfs; /* Netfslib context and vfs inode */
struct p9_qid qid;
unsigned int cache_validity;
struct mutex v_mutex;
};
static inline struct v9fs_inode *V9FS_I(const struct inode *inode)
{
return container_of(inode, struct v9fs_inode, netfs.inode);
}
static inline struct fscache_cookie *v9fs_inode_cookie(struct v9fs_inode *v9inode)
{
#ifdef CONFIG_9P_FSCACHE
return netfs_i_cookie(&v9inode->netfs);
#else
return NULL;
#endif
}
static inline struct fscache_volume *v9fs_session_cache(struct v9fs_session_info *v9ses)
{
#ifdef CONFIG_9P_FSCACHE
return v9ses->fscache;
#else
return NULL;
#endif
}
extern int v9fs_show_options(struct seq_file *m, struct dentry *root);
struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
const char *dev_name, char *data);
extern void v9fs_session_close(struct v9fs_session_info *v9ses);
extern void v9fs_session_cancel(struct v9fs_session_info *v9ses);
extern void v9fs_session_begin_cancel(struct v9fs_session_info *v9ses);
extern struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);
extern int v9fs_vfs_unlink(struct inode *i, struct dentry *d);
extern int v9fs_vfs_rmdir(struct inode *i, struct dentry *d);
extern int v9fs_vfs_rename(struct mnt_idmap *idmap,
struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags);
extern struct inode *v9fs_inode_from_fid(struct v9fs_session_info *v9ses,
struct p9_fid *fid,
struct super_block *sb, int new);
extern const struct inode_operations v9fs_dir_inode_operations_dotl;
extern const struct inode_operations v9fs_file_inode_operations_dotl;
extern const struct inode_operations v9fs_symlink_inode_operations_dotl;
extern const struct netfs_request_ops v9fs_req_ops;
extern struct inode *v9fs_inode_from_fid_dotl(struct v9fs_session_info *v9ses,
struct p9_fid *fid,
struct super_block *sb, int new);
/* other default globals */
#define V9FS_PORT 564
#define V9FS_DEFUSER "nobody"
#define V9FS_DEFANAME ""
#define V9FS_DEFUID KUIDT_INIT(-2)
#define V9FS_DEFGID KGIDT_INIT(-2)
static inline struct v9fs_session_info *v9fs_inode2v9ses(struct inode *inode)
{
return inode->i_sb->s_fs_info;
}
static inline struct v9fs_session_info *v9fs_dentry2v9ses(struct dentry *dentry)
{
return dentry->d_sb->s_fs_info;
}
static inline int v9fs_proto_dotu(struct v9fs_session_info *v9ses)
{
return v9ses->flags & V9FS_PROTO_2000U;
}
static inline int v9fs_proto_dotl(struct v9fs_session_info *v9ses)
{
return v9ses->flags & V9FS_PROTO_2000L;
}
/**
* v9fs_get_inode_from_fid - Helper routine to populate an inode by
* issuing a attribute request
* @v9ses: session information
* @fid: fid to issue attribute request for
* @sb: superblock on which to create inode
*
*/
static inline struct inode *
v9fs_get_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
struct super_block *sb)
{
if (v9fs_proto_dotl(v9ses))
return v9fs_inode_from_fid_dotl(v9ses, fid, sb, 0);
else
return v9fs_inode_from_fid(v9ses, fid, sb, 0);
}
/**
* v9fs_get_new_inode_from_fid - Helper routine to populate an inode by
* issuing a attribute request
* @v9ses: session information
* @fid: fid to issue attribute request for
* @sb: superblock on which to create inode
*
*/
static inline struct inode *
v9fs_get_new_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
struct super_block *sb)
{
if (v9fs_proto_dotl(v9ses))
return v9fs_inode_from_fid_dotl(v9ses, fid, sb, 1);
else
return v9fs_inode_from_fid(v9ses, fid, sb, 1);
}
#endif
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