--- /dev/null
+/*
+ * Copyright (C) 2017 Oracle. All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_icache.h"
+#include "xfs_dir2.h"
+#include "xfs_dir2_priv.h"
+#include "xfs_ialloc.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+
+/* Set us up to scrub parents. */
+int
+xfs_scrub_setup_parent(
+ struct xfs_scrub_context *sc,
+ struct xfs_inode *ip)
+{
+ return xfs_scrub_setup_inode_contents(sc, ip, 0);
+}
+
+/* Parent pointers */
+
+/* Look for an entry in a parent pointing to this inode. */
+
+struct xfs_scrub_parent_ctx {
+ struct dir_context dc;
+ xfs_ino_t ino;
+ xfs_nlink_t nlink;
+};
+
+/* Look for a single entry in a directory pointing to an inode. */
+STATIC int
+xfs_scrub_parent_actor(
+ struct dir_context *dc,
+ const char *name,
+ int namelen,
+ loff_t pos,
+ u64 ino,
+ unsigned type)
+{
+ struct xfs_scrub_parent_ctx *spc;
+
+ spc = container_of(dc, struct xfs_scrub_parent_ctx, dc);
+ if (spc->ino == ino)
+ spc->nlink++;
+ return 0;
+}
+
+/* Count the number of dentries in the parent dir that point to this inode. */
+STATIC int
+xfs_scrub_parent_count_parent_dentries(
+ struct xfs_scrub_context *sc,
+ struct xfs_inode *parent,
+ xfs_nlink_t *nlink)
+{
+ struct xfs_scrub_parent_ctx spc = {
+ .dc.actor = xfs_scrub_parent_actor,
+ .dc.pos = 0,
+ .ino = sc->ip->i_ino,
+ .nlink = 0,
+ };
+ size_t bufsize;
+ loff_t oldpos;
+ uint lock_mode;
+ int error = 0;
+
+ /*
+ * If there are any blocks, read-ahead block 0 as we're almost
+ * certain to have the next operation be a read there. This is
+ * how we guarantee that the parent's extent map has been loaded,
+ * if there is one.
+ */
+ lock_mode = xfs_ilock_data_map_shared(parent);
+ if (parent->i_d.di_nextents > 0)
+ error = xfs_dir3_data_readahead(parent, 0, -1);
+ xfs_iunlock(parent, lock_mode);
+ if (error)
+ return error;
+
+ /*
+ * Iterate the parent dir to confirm that there is
+ * exactly one entry pointing back to the inode being
+ * scanned.
+ */
+ bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE,
+ parent->i_d.di_size);
+ oldpos = 0;
+ while (true) {
+ error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize);
+ if (error)
+ goto out;
+ if (oldpos == spc.dc.pos)
+ break;
+ oldpos = spc.dc.pos;
+ }
+ *nlink = spc.nlink;
+out:
+ return error;
+}
+
+/*
+ * Given the inode number of the alleged parent of the inode being
+ * scrubbed, try to validate that the parent has exactly one directory
+ * entry pointing back to the inode being scrubbed.
+ */
+STATIC int
+xfs_scrub_parent_validate(
+ struct xfs_scrub_context *sc,
+ xfs_ino_t dnum,
+ bool *try_again)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_inode *dp = NULL;
+ xfs_nlink_t expected_nlink;
+ xfs_nlink_t nlink;
+ int error;
+
+ *try_again = false;
+
+ /* '..' must not point to ourselves. */
+ if (sc->ip->i_ino == dnum) {
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out;
+ }
+
+ /*
+ * If we're an unlinked directory, the parent /won't/ have a link
+ * to us. Otherwise, it should have one link.
+ */
+ expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
+
+ /*
+ * Grab this parent inode. We release the inode before we
+ * cancel the scrub transaction. Since we're don't know a
+ * priori that releasing the inode won't trigger eofblocks
+ * cleanup (which allocates what would be a nested transaction)
+ * if the parent pointer erroneously points to a file, we
+ * can't use DONTCACHE here because DONTCACHE inodes can trigger
+ * immediate inactive cleanup of the inode.
+ */
+ error = xfs_iget(mp, sc->tp, dnum, 0, 0, &dp);
+ if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
+ goto out;
+ if (dp == sc->ip) {
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out_rele;
+ }
+
+ /*
+ * We prefer to keep the inode locked while we lock and search
+ * its alleged parent for a forward reference. If we can grab
+ * the iolock, validate the pointers and we're done. We must
+ * use nowait here to avoid an ABBA deadlock on the parent and
+ * the child inodes.
+ */
+ if (xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED)) {
+ error = xfs_scrub_parent_count_parent_dentries(sc, dp, &nlink);
+ if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0,
+ &error))
+ goto out_unlock;
+ if (nlink != expected_nlink)
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out_unlock;
+ }
+
+ /*
+ * The game changes if we get here. We failed to lock the parent,
+ * so we're going to try to verify both pointers while only holding
+ * one lock so as to avoid deadlocking with something that's actually
+ * trying to traverse down the directory tree.
+ */
+ xfs_iunlock(sc->ip, sc->ilock_flags);
+ sc->ilock_flags = 0;
+ xfs_ilock(dp, XFS_IOLOCK_SHARED);
+
+ /* Go looking for our dentry. */
+ error = xfs_scrub_parent_count_parent_dentries(sc, dp, &nlink);
+ if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
+ goto out_unlock;
+
+ /* Drop the parent lock, relock this inode. */
+ xfs_iunlock(dp, XFS_IOLOCK_SHARED);
+ sc->ilock_flags = XFS_IOLOCK_EXCL;
+ xfs_ilock(sc->ip, sc->ilock_flags);
+
+ /*
+ * If we're an unlinked directory, the parent /won't/ have a link
+ * to us. Otherwise, it should have one link. We have to re-set
+ * it here because we dropped the lock on sc->ip.
+ */
+ expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
+
+ /* Look up '..' to see if the inode changed. */
+ error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
+ if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
+ goto out_rele;
+
+ /* Drat, parent changed. Try again! */
+ if (dnum != dp->i_ino) {
+ iput(VFS_I(dp));
+ *try_again = true;
+ return 0;
+ }
+ iput(VFS_I(dp));
+
+ /*
+ * '..' didn't change, so check that there was only one entry
+ * for us in the parent.
+ */
+ if (nlink != expected_nlink)
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ return error;
+
+out_unlock:
+ xfs_iunlock(dp, XFS_IOLOCK_SHARED);
+out_rele:
+ iput(VFS_I(dp));
+out:
+ return error;
+}
+
+/* Scrub a parent pointer. */
+int
+xfs_scrub_parent(
+ struct xfs_scrub_context *sc)
+{
+ struct xfs_mount *mp = sc->mp;
+ xfs_ino_t dnum;
+ bool try_again;
+ int tries = 0;
+ int error;
+
+ /*
+ * If we're a directory, check that the '..' link points up to
+ * a directory that has one entry pointing to us.
+ */
+ if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
+ return -ENOENT;
+
+ /* We're not a special inode, are we? */
+ if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) {
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out;
+ }
+
+ /*
+ * The VFS grabs a read or write lock via i_rwsem before it reads
+ * or writes to a directory. If we've gotten this far we've
+ * already obtained IOLOCK_EXCL, which (since 4.10) is the same as
+ * getting a write lock on i_rwsem. Therefore, it is safe for us
+ * to drop the ILOCK here in order to do directory lookups.
+ */
+ sc->ilock_flags &= ~(XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
+ xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
+
+ /* Look up '..' */
+ error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
+ if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
+ goto out;
+ if (!xfs_verify_dir_ino(mp, dnum)) {
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out;
+ }
+
+ /* Is this the root dir? Then '..' must point to itself. */
+ if (sc->ip == mp->m_rootip) {
+ if (sc->ip->i_ino != mp->m_sb.sb_rootino ||
+ sc->ip->i_ino != dnum)
+ xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ goto out;
+ }
+
+ do {
+ error = xfs_scrub_parent_validate(sc, dnum, &try_again);
+ if (error)
+ goto out;
+ } while (try_again && ++tries < 20);
+
+ /*
+ * We gave it our best shot but failed, so mark this scrub
+ * incomplete. Userspace can decide if it wants to try again.
+ */
+ if (try_again && tries == 20)
+ xfs_scrub_set_incomplete(sc);
+out:
+ return error;
+}
projects / users / hch / xfs.git / commitdiff