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
  65         kfree(scb);
  66         _leave(" = %d", ret);
  67         return ret;
  68 }
  69
  70 /**
  71  * afs_sillyrename - Perform a silly-rename of a dentry
  72  *
  73  * AFS is stateless and the server doesn't know when the client is holding a
  74  * file open.  To prevent application problems when a file is unlinked while
  75  * it's still open, the client performs a "silly-rename".  That is, it renames
  76  * the file to a hidden file in the same directory, and only performs the
  77  * unlink once the last reference to it is put.
  78  *
  79  * The final cleanup is done during dentry_iput.
  80  */
  81 int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  82                     struct dentry *dentry, struct key *key)
  83 {
  84         static unsigned int sillycounter;
  85         struct dentry *sdentry = NULL;
  86         unsigned char silly[16];
  87         int ret = -EBUSY;
  88
  89         _enter("");
  90
  91         /* We don't allow a dentry to be silly-renamed twice. */
  92         if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
  93                 return -EBUSY;
  94
  95         sdentry = NULL;
  96         do {
  97                 int slen;
  98
  99                 dput(sdentry);
 100                 sillycounter++;
 101
 102                 /* Create a silly name.  Note that the ".__afs" prefix is
 103                  * understood by the salvager and must not be changed.
 104                  */
 105                 slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
 106                 sdentry = lookup_one_len(silly, dentry->d_parent, slen);
 107
 108                 /* N.B. Better to return EBUSY here ... it could be dangerous
 109                  * to delete the file while it's in use.
 110                  */
 111                 if (IS_ERR(sdentry))
 112                         goto out;
 113         } while (!d_is_negative(sdentry));
 114
 115         ihold(&vnode->vfs_inode);
 116
 117         ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
 118         switch (ret) {
 119         case 0:
 120                 /* The rename succeeded. */
 121                 d_move(dentry, sdentry);
 122                 break;
 123         case -ERESTARTSYS:
 124                 /* The result of the rename is unknown. Play it safe by forcing
 125                  * a new lookup.
 126                  */
 127                 d_drop(dentry);
 128                 d_drop(sdentry);
 129         }
 130
 131         iput(&vnode->vfs_inode);
 132         dput(sdentry);
 133 out:
 134         _leave(" = %d", ret);
 135         return ret;
 136 }
 137
 138 /*
 139  * Tell the server to remove a sillyrename file.
 140  */
 141 static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 142                                struct dentry *dentry, struct key *key)
 143 {
 144         struct afs_fs_cursor fc;
 145         struct afs_status_cb *scb;
 146         int ret = -ERESTARTSYS;
 147
 148         _enter("");
 149
 150         scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
 151         if (!scb)
 152                 return -ENOMEM;
 153
 154         trace_afs_silly_rename(vnode, true);
 155         if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
 156                 afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
 157
 158                 while (afs_select_fileserver(&fc)) {
 159                         fc.cb_break = afs_calc_vnode_cb_break(dvnode);
 160
 161                         if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
 162                             !test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
 163                                 yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
 164                                                     &scb[0], &scb[1]);
 165                                 if (fc.ac.error != -ECONNABORTED ||
 166                                     fc.ac.abort_code != RXGEN_OPCODE)
 167                                         continue;
 168                                 set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
 169                         }
 170
 171                         afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
 172                 }
 173
 174                 afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
 175                                         &dir_data_version, &scb[0]);
 176                 ret = afs_end_vnode_operation(&fc);
 177                 if (ret == 0) {
 178                         drop_nlink(&vnode->vfs_inode);
 179                         if (vnode->vfs_inode.i_nlink == 0) {
 180                                 set_bit(AFS_VNODE_DELETED, &vnode->flags);
 181                                 clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
 182                         }
 183                 }
 184                 if (ret == 0 &&
 185                     test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
 186                         afs_edit_dir_remove(dvnode, &dentry->d_name,
 187                                             afs_edit_dir_for_unlink);
 188         }
 189
 190         kfree(scb);
 191         _leave(" = %d", ret);
 192         return ret;
 193 }
 194
 195 /*
 196  * Remove sillyrename file on iput.
 197  */
 198 int afs_silly_iput(struct dentry *dentry, struct inode *inode)
 199 {
 200         struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
 201         struct afs_vnode *vnode = AFS_FS_I(inode);
 202         struct dentry *alias;
 203         int ret;
 204
 205         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 206
 207         _enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
 208
 209         down_read(&dvnode->rmdir_lock);
 210
 211         alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
 212         if (IS_ERR(alias)) {
 213                 up_read(&dvnode->rmdir_lock);
 214                 return 0;
 215         }
 216
 217         if (!d_in_lookup(alias)) {
 218                 /* We raced with lookup...  See if we need to transfer the
 219                  * sillyrename information to the aliased dentry.
 220                  */
 221                 ret = 0;
 222                 spin_lock(&alias->d_lock);
 223                 if (d_really_is_positive(alias) &&
 224                     !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
 225                         alias->d_flags |= DCACHE_NFSFS_RENAMED;
 226                         ret = 1;
 227                 }
 228                 spin_unlock(&alias->d_lock);
 229                 up_read(&dvnode->rmdir_lock);
 230                 dput(alias);
 231                 return ret;
 232         }
 233
 234         /* Stop lock-release from complaining. */
 235         spin_lock(&vnode->lock);
 236         vnode->lock_state = AFS_VNODE_LOCK_DELETED;
 237         trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
 238         spin_unlock(&vnode->lock);
 239
 240         afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
 241         up_read(&dvnode->rmdir_lock);
 242         d_lookup_done(alias);
 243         dput(alias);
 244         return 1;
 245 }