1 /* 2 * Copyright (C) 2017 Oracle. All Rights Reserved. 3 * 4 * Author: Darrick J. Wong <darrick.wong@oracle.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 2 9 * of the License, or (at your option) any later version. 10 * 11 * This program is distributed in the hope that it would be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. 19 */ 20 #include "xfs.h" 21 #include "xfs_fs.h" 22 #include "xfs_shared.h" 23 #include "xfs_format.h" 24 #include "xfs_trans_resv.h" 25 #include "xfs_mount.h" 26 #include "xfs_defer.h" 27 #include "xfs_btree.h" 28 #include "xfs_bit.h" 29 #include "xfs_log_format.h" 30 #include "xfs_trans.h" 31 #include "xfs_sb.h" 32 #include "xfs_inode.h" 33 #include "xfs_icache.h" 34 #include "xfs_dir2.h" 35 #include "xfs_dir2_priv.h" 36 #include "xfs_ialloc.h" 37 #include "scrub/xfs_scrub.h" 38 #include "scrub/scrub.h" 39 #include "scrub/common.h" 40 #include "scrub/trace.h" 41 42 /* Set us up to scrub parents. */ 43 int 44 xfs_scrub_setup_parent( 45 struct xfs_scrub_context *sc, 46 struct xfs_inode *ip) 47 { 48 return xfs_scrub_setup_inode_contents(sc, ip, 0); 49 } 50 51 /* Parent pointers */ 52 53 /* Look for an entry in a parent pointing to this inode. */ 54 55 struct xfs_scrub_parent_ctx { 56 struct dir_context dc; 57 xfs_ino_t ino; 58 xfs_nlink_t nlink; 59 }; 60 61 /* Look for a single entry in a directory pointing to an inode. */ 62 STATIC int 63 xfs_scrub_parent_actor( 64 struct dir_context *dc, 65 const char *name, 66 int namelen, 67 loff_t pos, 68 u64 ino, 69 unsigned type) 70 { 71 struct xfs_scrub_parent_ctx *spc; 72 73 spc = container_of(dc, struct xfs_scrub_parent_ctx, dc); 74 if (spc->ino == ino) 75 spc->nlink++; 76 return 0; 77 } 78 79 /* Count the number of dentries in the parent dir that point to this inode. */ 80 STATIC int 81 xfs_scrub_parent_count_parent_dentries( 82 struct xfs_scrub_context *sc, 83 struct xfs_inode *parent, 84 xfs_nlink_t *nlink) 85 { 86 struct xfs_scrub_parent_ctx spc = { 87 .dc.actor = xfs_scrub_parent_actor, 88 .dc.pos = 0, 89 .ino = sc->ip->i_ino, 90 .nlink = 0, 91 }; 92 size_t bufsize; 93 loff_t oldpos; 94 uint lock_mode; 95 int error = 0; 96 97 /* 98 * If there are any blocks, read-ahead block 0 as we're almost 99 * certain to have the next operation be a read there. This is 100 * how we guarantee that the parent's extent map has been loaded, 101 * if there is one. 102 */ 103 lock_mode = xfs_ilock_data_map_shared(parent); 104 if (parent->i_d.di_nextents > 0) 105 error = xfs_dir3_data_readahead(parent, 0, -1); 106 xfs_iunlock(parent, lock_mode); 107 if (error) 108 return error; 109 110 /* 111 * Iterate the parent dir to confirm that there is 112 * exactly one entry pointing back to the inode being 113 * scanned. 114 */ 115 bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE, 116 parent->i_d.di_size); 117 oldpos = 0; 118 while (true) { 119 error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize); 120 if (error) 121 goto out; 122 if (oldpos == spc.dc.pos) 123 break; 124 oldpos = spc.dc.pos; 125 } 126 *nlink = spc.nlink; 127 out: 128 return error; 129 } 130 131 /* 132 * Given the inode number of the alleged parent of the inode being 133 * scrubbed, try to validate that the parent has exactly one directory 134 * entry pointing back to the inode being scrubbed. 135 */ 136 STATIC int 137 xfs_scrub_parent_validate( 138 struct xfs_scrub_context *sc, 139 xfs_ino_t dnum, 140 bool *try_again) 141 { 142 struct xfs_mount *mp = sc->mp; 143 struct xfs_inode *dp = NULL; 144 xfs_nlink_t expected_nlink; 145 xfs_nlink_t nlink; 146 int error = 0; 147 148 *try_again = false; 149 150 /* '..' must not point to ourselves. */ 151 if (sc->ip->i_ino == dnum) { 152 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 153 goto out; 154 } 155 156 /* 157 * If we're an unlinked directory, the parent /won't/ have a link 158 * to us. Otherwise, it should have one link. 159 */ 160 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; 161 162 /* 163 * Grab this parent inode. We release the inode before we 164 * cancel the scrub transaction. Since we're don't know a 165 * priori that releasing the inode won't trigger eofblocks 166 * cleanup (which allocates what would be a nested transaction) 167 * if the parent pointer erroneously points to a file, we 168 * can't use DONTCACHE here because DONTCACHE inodes can trigger 169 * immediate inactive cleanup of the inode. 170 */ 171 error = xfs_iget(mp, sc->tp, dnum, 0, 0, &dp); 172 if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 173 goto out; 174 if (dp == sc->ip) { 175 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 176 goto out_rele; 177 } 178 179 /* 180 * We prefer to keep the inode locked while we lock and search 181 * its alleged parent for a forward reference. If we can grab 182 * the iolock, validate the pointers and we're done. We must 183 * use nowait here to avoid an ABBA deadlock on the parent and 184 * the child inodes. 185 */ 186 if (xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED)) { 187 error = xfs_scrub_parent_count_parent_dentries(sc, dp, &nlink); 188 if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, 189 &error)) 190 goto out_unlock; 191 if (nlink != expected_nlink) 192 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 193 goto out_unlock; 194 } 195 196 /* 197 * The game changes if we get here. We failed to lock the parent, 198 * so we're going to try to verify both pointers while only holding 199 * one lock so as to avoid deadlocking with something that's actually 200 * trying to traverse down the directory tree. 201 */ 202 xfs_iunlock(sc->ip, sc->ilock_flags); 203 sc->ilock_flags = 0; 204 xfs_ilock(dp, XFS_IOLOCK_SHARED); 205 206 /* Go looking for our dentry. */ 207 error = xfs_scrub_parent_count_parent_dentries(sc, dp, &nlink); 208 if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 209 goto out_unlock; 210 211 /* Drop the parent lock, relock this inode. */ 212 xfs_iunlock(dp, XFS_IOLOCK_SHARED); 213 sc->ilock_flags = XFS_IOLOCK_EXCL; 214 xfs_ilock(sc->ip, sc->ilock_flags); 215 216 /* 217 * If we're an unlinked directory, the parent /won't/ have a link 218 * to us. Otherwise, it should have one link. We have to re-set 219 * it here because we dropped the lock on sc->ip. 220 */ 221 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; 222 223 /* Look up '..' to see if the inode changed. */ 224 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); 225 if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 226 goto out_rele; 227 228 /* Drat, parent changed. Try again! */ 229 if (dnum != dp->i_ino) { 230 iput(VFS_I(dp)); 231 *try_again = true; 232 return 0; 233 } 234 iput(VFS_I(dp)); 235 236 /* 237 * '..' didn't change, so check that there was only one entry 238 * for us in the parent. 239 */ 240 if (nlink != expected_nlink) 241 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 242 return error; 243 244 out_unlock: 245 xfs_iunlock(dp, XFS_IOLOCK_SHARED); 246 out_rele: 247 iput(VFS_I(dp)); 248 out: 249 return error; 250 } 251 252 /* Scrub a parent pointer. */ 253 int 254 xfs_scrub_parent( 255 struct xfs_scrub_context *sc) 256 { 257 struct xfs_mount *mp = sc->mp; 258 xfs_ino_t dnum; 259 bool try_again; 260 int tries = 0; 261 int error = 0; 262 263 /* 264 * If we're a directory, check that the '..' link points up to 265 * a directory that has one entry pointing to us. 266 */ 267 if (!S_ISDIR(VFS_I(sc->ip)->i_mode)) 268 return -ENOENT; 269 270 /* We're not a special inode, are we? */ 271 if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) { 272 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 273 goto out; 274 } 275 276 /* 277 * The VFS grabs a read or write lock via i_rwsem before it reads 278 * or writes to a directory. If we've gotten this far we've 279 * already obtained IOLOCK_EXCL, which (since 4.10) is the same as 280 * getting a write lock on i_rwsem. Therefore, it is safe for us 281 * to drop the ILOCK here in order to do directory lookups. 282 */ 283 sc->ilock_flags &= ~(XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); 284 xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); 285 286 /* Look up '..' */ 287 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); 288 if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 289 goto out; 290 if (!xfs_verify_dir_ino(mp, dnum)) { 291 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 292 goto out; 293 } 294 295 /* Is this the root dir? Then '..' must point to itself. */ 296 if (sc->ip == mp->m_rootip) { 297 if (sc->ip->i_ino != mp->m_sb.sb_rootino || 298 sc->ip->i_ino != dnum) 299 xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 300 goto out; 301 } 302 303 do { 304 error = xfs_scrub_parent_validate(sc, dnum, &try_again); 305 if (error) 306 goto out; 307 } while (try_again && ++tries < 20); 308 309 /* 310 * We gave it our best shot but failed, so mark this scrub 311 * incomplete. Userspace can decide if it wants to try again. 312 */ 313 if (try_again && tries == 20) 314 xfs_scrub_set_incomplete(sc); 315 out: 316 return error; 317 } 318