fs/afs/dir_silly.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* AFS silly rename handling
   3  *
   4  * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  * - Derived from NFS's sillyrename.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/fs.h>
  11 #include <linux/namei.h>
  12 #include <linux/fsnotify.h>
  13 #include "internal.h"
  14
  15 /*
  16  * Actually perform the silly rename step.
  17  */
  18 static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  19                                struct dentry *old, struct dentry *new,
  20                                struct key *key)
  21 {
  22         struct afs_fs_cursor fc;
  23         struct afs_status_cb *scb;
  24         int ret = -ERESTARTSYS;
  25
  26         _enter("%pd,%pd", old, new);
  27
  28         scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
  29         if (!scb)
  30                 return -ENOMEM;
  31
  32         trace_afs_silly_rename(vnode, false);
  33         if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
  34                 afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
  35
  36                 while (afs_select_fileserver(&fc)) {
  37                         fc.cb_break = afs_calc_vnode_cb_break(dvnode);
  38                         afs_fs_rename(&fc, old->d_name.name,
  39                                       dvnode, new->d_name.name,
  40                                       scb, scb);
  41                 }
  42
  43                 afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
  44                                         &dir_data_version, scb);
  45                 ret = afs_end_vnode_operation(&fc);
  46         }
  47
  48         if (ret == 0) {
  49                 spin_lock(&old->d_lock);
  50                 old->d_flags |= DCACHE_NFSFS_RENAMED;
  51                 spin_unlock(&old->d_lock);
  52                 if (dvnode->silly_key != key) {
  53                         key_put(dvnode->silly_key);
  54                         dvnode->silly_key = key_get(key);
  55                 }
  56
  57                 if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
  58                         afs_edit_dir_remove(dvnode, &old->d_name,
  59                                             afs_edit_dir_for_silly_0);
  60                 if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
  61                         afs_edit_dir_add(dvnode, &new->d_name,
  62                                          &vnode->fid, afs_edit_dir_for_silly_1);
  63
  64                 /* vfs_unlink and the like do not issue this when a file is
  65                  * sillyrenamed, so do it here.
  66                  */
  67                 fsnotify_nameremove(old, 0);
  68         }
  69
  70         kfree(scb);
  71         _leave(" = %d", ret);
  72         return ret;
  73 }
  74
  75 /**
  76  * afs_sillyrename - Perform a silly-rename of a dentry
  77  *
  78  * AFS is stateless and the server doesn't know when the client is holding a
  79  * file open.  To prevent application problems when a file is unlinked while
  80  * it's still open, the client performs a "silly-rename".  That is, it renames
  81  * the file to a hidden file in the same directory, and only performs the
  82  * unlink once the last reference to it is put.
  83  *
  84  * The final cleanup is done during dentry_iput.
  85  */
  86 int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  87                     struct dentry *dentry, struct key *key)
  88 {
  89         static unsigned int sillycounter;
  90         struct dentry *sdentry = NULL;
  91         unsigned char silly[16];
  92         int ret = -EBUSY;
  93
  94         _enter("");
  95
  96         /* We don't allow a dentry to be silly-renamed twice. */
  97         if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
  98                 return -EBUSY;
  99
 100         sdentry = NULL;
 101         do {
 102                 int slen;
 103
 104                 dput(sdentry);
 105                 sillycounter++;
 106
 107                 /* Create a silly name.  Note that the ".__afs" prefix is
 108                  * understood by the salvager and must not be changed.
 109                  */
 110                 slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
 111                 sdentry = lookup_one_len(silly, dentry->d_parent, slen);
 112
 113                 /* N.B. Better to return EBUSY here ... it could be dangerous
 114                  * to delete the file while it's in use.
 115                  */
 116                 if (IS_ERR(sdentry))
 117                         goto out;
 118         } while (!d_is_negative(sdentry));
 119
 120         ihold(&vnode->vfs_inode);
 121
 122         ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
 123         switch (ret) {
 124         case 0:
 125                 /* The rename succeeded. */
 126                 d_move(dentry, sdentry);
 127                 break;
 128         case -ERESTARTSYS:
 129                 /* The result of the rename is unknown. Play it safe by forcing
 130                  * a new lookup.
 131                  */
 132                 d_drop(dentry);
 133                 d_drop(sdentry);
 134         }
 135
 136         iput(&vnode->vfs_inode);
 137         dput(sdentry);
 138 out:
 139         _leave(" = %d", ret);
 140         return ret;
 141 }
 142
 143 /*
 144  * Tell the server to remove a sillyrename file.
 145  */
 146 static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 147                                struct dentry *dentry, struct key *key)
 148 {
 149         struct afs_fs_cursor fc;
 150         struct afs_status_cb *scb;
 151         int ret = -ERESTARTSYS;
 152
 153         _enter("");
 154
 155         scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
 156         if (!scb)
 157                 return -ENOMEM;
 158
 159         trace_afs_silly_rename(vnode, true);
 160         if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
 161                 afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
 162
 163                 while (afs_select_fileserver(&fc)) {
 164                         fc.cb_break = afs_calc_vnode_cb_break(dvnode);
 165
 166                         if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
 167                             !test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
 168                                 yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
 169                                                     &scb[0], &scb[1]);
 170                                 if (fc.ac.error != -ECONNABORTED ||
 171                                     fc.ac.abort_code != RXGEN_OPCODE)
 172                                         continue;
 173                                 set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
 174                         }
 175
 176                         afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
 177                 }
 178
 179                 afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
 180                                         &dir_data_version, &scb[0]);
 181                 ret = afs_end_vnode_operation(&fc);
 182                 if (ret == 0) {
 183                         drop_nlink(&vnode->vfs_inode);
 184                         if (vnode->vfs_inode.i_nlink == 0) {
 185                                 set_bit(AFS_VNODE_DELETED, &vnode->flags);
 186                                 clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
 187                         }
 188                 }
 189                 if (ret == 0 &&
 190                     test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
 191                         afs_edit_dir_remove(dvnode, &dentry->d_name,
 192                                             afs_edit_dir_for_unlink);
 193         }
 194
 195         kfree(scb);
 196         _leave(" = %d", ret);
 197         return ret;
 198 }
 199
 200 /*
 201  * Remove sillyrename file on iput.
 202  */
 203 int afs_silly_iput(struct dentry *dentry, struct inode *inode)
 204 {
 205         struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
 206         struct afs_vnode *vnode = AFS_FS_I(inode);
 207         struct dentry *alias;
 208         int ret;
 209
 210         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 211
 212         _enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
 213
 214         down_read(&dvnode->rmdir_lock);
 215
 216         alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
 217         if (IS_ERR(alias)) {
 218                 up_read(&dvnode->rmdir_lock);
 219                 return 0;
 220         }
 221
 222         if (!d_in_lookup(alias)) {
 223                 /* We raced with lookup...  See if we need to transfer the
 224                  * sillyrename information to the aliased dentry.
 225                  */
 226                 ret = 0;
 227                 spin_lock(&alias->d_lock);
 228                 if (d_really_is_positive(alias) &&
 229                     !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
 230                         alias->d_flags |= DCACHE_NFSFS_RENAMED;
 231                         ret = 1;
 232                 }
 233                 spin_unlock(&alias->d_lock);
 234                 up_read(&dvnode->rmdir_lock);
 235                 dput(alias);
 236                 return ret;
 237         }
 238
 239         /* Stop lock-release from complaining. */
 240         spin_lock(&vnode->lock);
 241         vnode->lock_state = AFS_VNODE_LOCK_DELETED;
 242         trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
 243         spin_unlock(&vnode->lock);
 244
 245         afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
 246         up_read(&dvnode->rmdir_lock);
 247         d_lookup_done(alias);
 248         dput(alias);
 249         return 1;
 250 }