| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * V9FS FID Management |
| * |
| * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net> |
| * Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com> |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/errno.h> |
| #include <linux/fs.h> |
| #include <linux/slab.h> |
| #include <linux/sched.h> |
| #include <linux/idr.h> |
| #include <net/9p/9p.h> |
| #include <net/9p/client.h> |
| |
| #include "v9fs.h" |
| #include "v9fs_vfs.h" |
| #include "fid.h" |
| |
| static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid) |
| { |
| hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata); |
| } |
| |
| |
| /** |
| * v9fs_fid_add - add a fid to a dentry |
| * @dentry: dentry that the fid is being added to |
| * @fid: fid to add |
| * |
| */ |
| void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid) |
| { |
| spin_lock(&dentry->d_lock); |
| __add_fid(dentry, fid); |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /** |
| * v9fs_fid_find_inode - search for an open fid off of the inode list |
| * @inode: return a fid pointing to a specific inode |
| * @uid: return a fid belonging to the specified user |
| * |
| */ |
| |
| static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid) |
| { |
| struct hlist_head *h; |
| struct p9_fid *fid, *ret = NULL; |
| |
| p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode); |
| |
| spin_lock(&inode->i_lock); |
| h = (struct hlist_head *)&inode->i_private; |
| hlist_for_each_entry(fid, h, ilist) { |
| if (uid_eq(fid->uid, uid)) { |
| refcount_inc(&fid->count); |
| ret = fid; |
| break; |
| } |
| } |
| spin_unlock(&inode->i_lock); |
| return ret; |
| } |
| |
| /** |
| * v9fs_open_fid_add - add an open fid to an inode |
| * @inode: inode that the fid is being added to |
| * @fid: fid to add |
| * |
| */ |
| |
| void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid) |
| { |
| spin_lock(&inode->i_lock); |
| hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private); |
| spin_unlock(&inode->i_lock); |
| } |
| |
| |
| /** |
| * v9fs_fid_find - retrieve a fid that belongs to the specified uid |
| * @dentry: dentry to look for fid in |
| * @uid: return fid that belongs to the specified user |
| * @any: if non-zero, return any fid associated with the dentry |
| * |
| */ |
| |
| static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) |
| { |
| struct p9_fid *fid, *ret; |
| |
| p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n", |
| dentry, dentry, from_kuid(&init_user_ns, uid), |
| any); |
| ret = NULL; |
| /* we'll recheck under lock if there's anything to look in */ |
| if (dentry->d_fsdata) { |
| struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; |
| |
| spin_lock(&dentry->d_lock); |
| hlist_for_each_entry(fid, h, dlist) { |
| if (any || uid_eq(fid->uid, uid)) { |
| ret = fid; |
| refcount_inc(&ret->count); |
| break; |
| } |
| } |
| spin_unlock(&dentry->d_lock); |
| } else { |
| if (dentry->d_inode) |
| ret = v9fs_fid_find_inode(dentry->d_inode, uid); |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * We need to hold v9ses->rename_sem as long as we hold references |
| * to returned path array. Array element contain pointers to |
| * dentry names. |
| */ |
| static int build_path_from_dentry(struct v9fs_session_info *v9ses, |
| struct dentry *dentry, const unsigned char ***names) |
| { |
| int n = 0, i; |
| const unsigned char **wnames; |
| struct dentry *ds; |
| |
| for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) |
| n++; |
| |
| wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL); |
| if (!wnames) |
| goto err_out; |
| |
| for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) |
| wnames[i] = ds->d_name.name; |
| |
| *names = wnames; |
| return n; |
| err_out: |
| return -ENOMEM; |
| } |
| |
| static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, |
| kuid_t uid, int any) |
| { |
| struct dentry *ds; |
| const unsigned char **wnames, *uname; |
| int i, n, l, clone, access; |
| struct v9fs_session_info *v9ses; |
| struct p9_fid *fid, *old_fid; |
| |
| v9ses = v9fs_dentry2v9ses(dentry); |
| access = v9ses->flags & V9FS_ACCESS_MASK; |
| fid = v9fs_fid_find(dentry, uid, any); |
| if (fid) |
| return fid; |
| /* |
| * we don't have a matching fid. To do a TWALK we need |
| * parent fid. We need to prevent rename when we want to |
| * look at the parent. |
| */ |
| down_read(&v9ses->rename_sem); |
| ds = dentry->d_parent; |
| fid = v9fs_fid_find(ds, uid, any); |
| if (fid) { |
| /* Found the parent fid do a lookup with that */ |
| struct p9_fid *ofid = fid; |
| |
| fid = p9_client_walk(ofid, 1, &dentry->d_name.name, 1); |
| p9_client_clunk(ofid); |
| goto fid_out; |
| } |
| up_read(&v9ses->rename_sem); |
| |
| /* start from the root and try to do a lookup */ |
| fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); |
| if (!fid) { |
| /* the user is not attached to the fs yet */ |
| if (access == V9FS_ACCESS_SINGLE) |
| return ERR_PTR(-EPERM); |
| |
| if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) |
| uname = NULL; |
| else |
| uname = v9ses->uname; |
| |
| fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, |
| v9ses->aname); |
| if (IS_ERR(fid)) |
| return fid; |
| |
| refcount_inc(&fid->count); |
| v9fs_fid_add(dentry->d_sb->s_root, fid); |
| } |
| /* If we are root ourself just return that */ |
| if (dentry->d_sb->s_root == dentry) |
| return fid; |
| /* |
| * Do a multipath walk with attached root. |
| * When walking parent we need to make sure we |
| * don't have a parallel rename happening |
| */ |
| down_read(&v9ses->rename_sem); |
| n = build_path_from_dentry(v9ses, dentry, &wnames); |
| if (n < 0) { |
| fid = ERR_PTR(n); |
| goto err_out; |
| } |
| old_fid = fid; |
| clone = 1; |
| i = 0; |
| while (i < n) { |
| l = min(n - i, P9_MAXWELEM); |
| /* |
| * We need to hold rename lock when doing a multipath |
| * walk to ensure none of the patch component change |
| */ |
| fid = p9_client_walk(fid, l, &wnames[i], clone); |
| /* non-cloning walk will return the same fid */ |
| if (fid != old_fid) { |
| p9_client_clunk(old_fid); |
| old_fid = fid; |
| } |
| if (IS_ERR(fid)) { |
| kfree(wnames); |
| goto err_out; |
| } |
| i += l; |
| clone = 0; |
| } |
| kfree(wnames); |
| fid_out: |
| if (!IS_ERR(fid)) { |
| spin_lock(&dentry->d_lock); |
| if (d_unhashed(dentry)) { |
| spin_unlock(&dentry->d_lock); |
| p9_client_clunk(fid); |
| fid = ERR_PTR(-ENOENT); |
| } else { |
| __add_fid(dentry, fid); |
| refcount_inc(&fid->count); |
| spin_unlock(&dentry->d_lock); |
| } |
| } |
| err_out: |
| up_read(&v9ses->rename_sem); |
| return fid; |
| } |
| |
| /** |
| * v9fs_fid_lookup - lookup for a fid, try to walk if not found |
| * @dentry: dentry to look for fid in |
| * |
| * Look for a fid in the specified dentry for the current user. |
| * If no fid is found, try to create one walking from a fid from the parent |
| * dentry (if it has one), or the root dentry. If the user haven't accessed |
| * the fs yet, attach now and walk from the root. |
| */ |
| |
| struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) |
| { |
| kuid_t uid; |
| int any, access; |
| struct v9fs_session_info *v9ses; |
| |
| v9ses = v9fs_dentry2v9ses(dentry); |
| access = v9ses->flags & V9FS_ACCESS_MASK; |
| switch (access) { |
| case V9FS_ACCESS_SINGLE: |
| case V9FS_ACCESS_USER: |
| case V9FS_ACCESS_CLIENT: |
| uid = current_fsuid(); |
| any = 0; |
| break; |
| |
| case V9FS_ACCESS_ANY: |
| uid = v9ses->uid; |
| any = 1; |
| break; |
| |
| default: |
| uid = INVALID_UID; |
| any = 0; |
| break; |
| } |
| return v9fs_fid_lookup_with_uid(dentry, uid, any); |
| } |
| |
| struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) |
| { |
| int err; |
| struct p9_fid *fid, *ofid; |
| |
| ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); |
| fid = clone_fid(ofid); |
| if (IS_ERR(fid)) |
| goto error_out; |
| p9_client_clunk(ofid); |
| /* |
| * writeback fid will only be used to write back the |
| * dirty pages. We always request for the open fid in read-write |
| * mode so that a partial page write which result in page |
| * read can work. |
| */ |
| err = p9_client_open(fid, O_RDWR); |
| if (err < 0) { |
| p9_client_clunk(fid); |
| fid = ERR_PTR(err); |
| goto error_out; |
| } |
| error_out: |
| return fid; |
| } |