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30d61efe11
9p wants to be able to build a path from given dentry to fs root and keep it valid over a blocking operation. ->s_vfs_rename_mutex would be a natural candidate, but there are places where we need that and where we have no way to tell if ->s_vfs_rename_mutex is already held deeper in callchain. Moreover, it's only held for cross-directory renames; name changes within the same directory happen without it. Solution: * have d_move() done in ->rename() rather than in its caller * maintain a 9p-private rwsem (per-filesystem) * hold it exclusive over the relevant part of ->rename() * hold it shared over the places where we want the path. That almost works. FS_RENAME_DOES_D_MOVE is enough to put all d_move() and d_exchange() calls under filesystem's control. However, there's also __d_unalias(), which isn't covered by any of that. If ->lookup() hits a directory inode with preexisting dentry elsewhere (due to e.g. rename done on server behind our back), d_splice_alias() called by ->lookup() will move/rename that alias. Add a couple of optional methods, so that __d_unalias() would do if alias->d_op->d_unalias_trylock != NULL if (!alias->d_op->d_unalias_trylock(alias)) fail (resulting in -ESTALE from lookup) __d_move(...) if alias->d_op->d_unalias_unlock != NULL alias->d_unalias_unlock(alias) where it currently does __d_move(). 9p instances do down_write_trylock() and up_write() of ->rename_mutex. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
134 lines
3.2 KiB
C
134 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* This file contians vfs dentry ops for the 9P2000 protocol.
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*
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* Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
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* Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
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*/
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/pagemap.h>
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#include <linux/stat.h>
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#include <linux/string.h>
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#include <linux/namei.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <net/9p/9p.h>
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#include <net/9p/client.h>
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#include "v9fs.h"
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#include "v9fs_vfs.h"
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#include "fid.h"
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/**
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* v9fs_cached_dentry_delete - called when dentry refcount equals 0
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* @dentry: dentry in question
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*
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*/
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static int v9fs_cached_dentry_delete(const struct dentry *dentry)
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{
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p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p)\n",
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dentry, dentry);
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/* Don't cache negative dentries */
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if (d_really_is_negative(dentry))
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return 1;
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return 0;
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}
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/**
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* v9fs_dentry_release - called when dentry is going to be freed
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* @dentry: dentry that is being release
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*
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*/
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static void v9fs_dentry_release(struct dentry *dentry)
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{
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struct hlist_node *p, *n;
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struct hlist_head head;
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p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p)\n",
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dentry, dentry);
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spin_lock(&dentry->d_lock);
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hlist_move_list((struct hlist_head *)&dentry->d_fsdata, &head);
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spin_unlock(&dentry->d_lock);
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hlist_for_each_safe(p, n, &head)
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p9_fid_put(hlist_entry(p, struct p9_fid, dlist));
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}
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static int __v9fs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct p9_fid *fid;
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struct inode *inode;
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struct v9fs_inode *v9inode;
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if (flags & LOOKUP_RCU)
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return -ECHILD;
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inode = d_inode(dentry);
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if (!inode)
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goto out_valid;
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v9inode = V9FS_I(inode);
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if (v9inode->cache_validity & V9FS_INO_INVALID_ATTR) {
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int retval;
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struct v9fs_session_info *v9ses;
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fid = v9fs_fid_lookup(dentry);
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if (IS_ERR(fid))
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return PTR_ERR(fid);
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v9ses = v9fs_inode2v9ses(inode);
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if (v9fs_proto_dotl(v9ses))
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retval = v9fs_refresh_inode_dotl(fid, inode);
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else
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retval = v9fs_refresh_inode(fid, inode);
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p9_fid_put(fid);
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if (retval == -ENOENT)
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return 0;
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if (retval < 0)
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return retval;
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}
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out_valid:
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return 1;
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}
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static int v9fs_lookup_revalidate(struct inode *dir, const struct qstr *name,
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struct dentry *dentry, unsigned int flags)
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{
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return __v9fs_lookup_revalidate(dentry, flags);
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}
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static bool v9fs_dentry_unalias_trylock(const struct dentry *dentry)
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{
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struct v9fs_session_info *v9ses = v9fs_dentry2v9ses(dentry);
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return down_write_trylock(&v9ses->rename_sem);
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}
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static void v9fs_dentry_unalias_unlock(const struct dentry *dentry)
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{
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struct v9fs_session_info *v9ses = v9fs_dentry2v9ses(dentry);
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up_write(&v9ses->rename_sem);
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}
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const struct dentry_operations v9fs_cached_dentry_operations = {
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.d_revalidate = v9fs_lookup_revalidate,
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.d_weak_revalidate = __v9fs_lookup_revalidate,
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.d_delete = v9fs_cached_dentry_delete,
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.d_release = v9fs_dentry_release,
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.d_unalias_trylock = v9fs_dentry_unalias_trylock,
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.d_unalias_unlock = v9fs_dentry_unalias_unlock,
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};
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const struct dentry_operations v9fs_dentry_operations = {
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.d_delete = always_delete_dentry,
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.d_release = v9fs_dentry_release,
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.d_unalias_trylock = v9fs_dentry_unalias_trylock,
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.d_unalias_unlock = v9fs_dentry_unalias_unlock,
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};
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