// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (C) 2017 Oracle. All Rights Reserved.
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* Author: Darrick J. Wong <darrick.wong@oracle.com>
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*/
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#include "xfs.h"
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#include "xfs_fs.h"
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#include "xfs_shared.h"
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#include "xfs_format.h"
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#include "xfs_trans_resv.h"
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#include "xfs_mount.h"
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#include "xfs_log_format.h"
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#include "xfs_inode.h"
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#include "xfs_icache.h"
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#include "xfs_dir2.h"
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#include "xfs_dir2_priv.h"
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#include "scrub/scrub.h"
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#include "scrub/common.h"
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/* Set us up to scrub parents. */
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int
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xchk_setup_parent(
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struct xfs_scrub *sc,
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struct xfs_inode *ip)
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{
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return xchk_setup_inode_contents(sc, ip, 0);
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}
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/* Parent pointers */
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/* Look for an entry in a parent pointing to this inode. */
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struct xchk_parent_ctx {
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struct dir_context dc;
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struct xfs_scrub *sc;
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xfs_ino_t ino;
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xfs_nlink_t nlink;
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bool cancelled;
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};
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/* Look for a single entry in a directory pointing to an inode. */
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STATIC int
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xchk_parent_actor(
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struct dir_context *dc,
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const char *name,
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int namelen,
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loff_t pos,
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u64 ino,
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unsigned type)
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{
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struct xchk_parent_ctx *spc;
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int error = 0;
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spc = container_of(dc, struct xchk_parent_ctx, dc);
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if (spc->ino == ino)
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spc->nlink++;
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/*
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* If we're facing a fatal signal, bail out. Store the cancellation
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* status separately because the VFS readdir code squashes error codes
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* into short directory reads.
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*/
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if (xchk_should_terminate(spc->sc, &error))
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spc->cancelled = true;
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return error;
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}
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/* Count the number of dentries in the parent dir that point to this inode. */
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STATIC int
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xchk_parent_count_parent_dentries(
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struct xfs_scrub *sc,
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struct xfs_inode *parent,
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xfs_nlink_t *nlink)
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{
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struct xchk_parent_ctx spc = {
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.dc.actor = xchk_parent_actor,
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.ino = sc->ip->i_ino,
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.sc = sc,
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};
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size_t bufsize;
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loff_t oldpos;
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uint lock_mode;
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int error = 0;
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/*
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* If there are any blocks, read-ahead block 0 as we're almost
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* certain to have the next operation be a read there. This is
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* how we guarantee that the parent's extent map has been loaded,
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* if there is one.
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*/
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lock_mode = xfs_ilock_data_map_shared(parent);
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if (parent->i_df.if_nextents > 0)
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error = xfs_dir3_data_readahead(parent, 0, 0);
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xfs_iunlock(parent, lock_mode);
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if (error)
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return error;
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/*
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* Iterate the parent dir to confirm that there is
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* exactly one entry pointing back to the inode being
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* scanned.
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*/
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bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE,
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parent->i_d.di_size);
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oldpos = 0;
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while (true) {
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error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize);
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if (error)
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goto out;
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if (spc.cancelled) {
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error = -EAGAIN;
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goto out;
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}
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if (oldpos == spc.dc.pos)
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break;
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oldpos = spc.dc.pos;
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}
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*nlink = spc.nlink;
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out:
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return error;
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}
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/*
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* Given the inode number of the alleged parent of the inode being
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* scrubbed, try to validate that the parent has exactly one directory
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* entry pointing back to the inode being scrubbed.
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*/
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STATIC int
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xchk_parent_validate(
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struct xfs_scrub *sc,
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xfs_ino_t dnum,
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bool *try_again)
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{
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struct xfs_mount *mp = sc->mp;
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struct xfs_inode *dp = NULL;
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xfs_nlink_t expected_nlink;
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xfs_nlink_t nlink;
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int error = 0;
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*try_again = false;
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if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
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goto out;
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/* '..' must not point to ourselves. */
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if (sc->ip->i_ino == dnum) {
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out;
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}
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/*
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* If we're an unlinked directory, the parent /won't/ have a link
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* to us. Otherwise, it should have one link.
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*/
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expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
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/*
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* Grab this parent inode. We release the inode before we
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* cancel the scrub transaction. Since we're don't know a
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* priori that releasing the inode won't trigger eofblocks
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* cleanup (which allocates what would be a nested transaction)
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* if the parent pointer erroneously points to a file, we
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* can't use DONTCACHE here because DONTCACHE inodes can trigger
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* immediate inactive cleanup of the inode.
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*
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* If _iget returns -EINVAL then the parent inode number is garbage
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* and the directory is corrupt. If the _iget returns -EFSCORRUPTED
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* or -EFSBADCRC then the parent is corrupt which is a cross
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* referencing error. Any other error is an operational error.
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*/
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error = xfs_iget(mp, sc->tp, dnum, XFS_IGET_UNTRUSTED, 0, &dp);
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if (error == -EINVAL) {
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error = -EFSCORRUPTED;
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xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error);
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goto out;
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}
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if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
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goto out;
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if (dp == sc->ip || !S_ISDIR(VFS_I(dp)->i_mode)) {
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out_rele;
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}
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/*
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* We prefer to keep the inode locked while we lock and search
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* its alleged parent for a forward reference. If we can grab
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* the iolock, validate the pointers and we're done. We must
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* use nowait here to avoid an ABBA deadlock on the parent and
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* the child inodes.
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*/
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if (xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED)) {
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error = xchk_parent_count_parent_dentries(sc, dp, &nlink);
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if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0,
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&error))
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goto out_unlock;
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if (nlink != expected_nlink)
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out_unlock;
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}
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/*
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* The game changes if we get here. We failed to lock the parent,
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* so we're going to try to verify both pointers while only holding
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* one lock so as to avoid deadlocking with something that's actually
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* trying to traverse down the directory tree.
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*/
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xfs_iunlock(sc->ip, sc->ilock_flags);
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sc->ilock_flags = 0;
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error = xchk_ilock_inverted(dp, XFS_IOLOCK_SHARED);
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if (error)
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goto out_rele;
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/* Go looking for our dentry. */
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error = xchk_parent_count_parent_dentries(sc, dp, &nlink);
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if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
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goto out_unlock;
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/* Drop the parent lock, relock this inode. */
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xfs_iunlock(dp, XFS_IOLOCK_SHARED);
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error = xchk_ilock_inverted(sc->ip, XFS_IOLOCK_EXCL);
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if (error)
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goto out_rele;
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sc->ilock_flags = XFS_IOLOCK_EXCL;
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/*
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* If we're an unlinked directory, the parent /won't/ have a link
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* to us. Otherwise, it should have one link. We have to re-set
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* it here because we dropped the lock on sc->ip.
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*/
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expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
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/* Look up '..' to see if the inode changed. */
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error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
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if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
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goto out_rele;
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/* Drat, parent changed. Try again! */
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if (dnum != dp->i_ino) {
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xfs_irele(dp);
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*try_again = true;
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return 0;
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}
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xfs_irele(dp);
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/*
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* '..' didn't change, so check that there was only one entry
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* for us in the parent.
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*/
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if (nlink != expected_nlink)
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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return error;
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out_unlock:
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xfs_iunlock(dp, XFS_IOLOCK_SHARED);
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out_rele:
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xfs_irele(dp);
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out:
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return error;
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}
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/* Scrub a parent pointer. */
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int
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xchk_parent(
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struct xfs_scrub *sc)
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{
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struct xfs_mount *mp = sc->mp;
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xfs_ino_t dnum;
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bool try_again;
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int tries = 0;
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int error = 0;
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/*
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* If we're a directory, check that the '..' link points up to
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* a directory that has one entry pointing to us.
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*/
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if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
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return -ENOENT;
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/* We're not a special inode, are we? */
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if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) {
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out;
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}
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/*
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* The VFS grabs a read or write lock via i_rwsem before it reads
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* or writes to a directory. If we've gotten this far we've
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* already obtained IOLOCK_EXCL, which (since 4.10) is the same as
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* getting a write lock on i_rwsem. Therefore, it is safe for us
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* to drop the ILOCK here in order to do directory lookups.
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*/
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sc->ilock_flags &= ~(XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
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xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
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/* Look up '..' */
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error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
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if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
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goto out;
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if (!xfs_verify_dir_ino(mp, dnum)) {
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out;
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}
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/* Is this the root dir? Then '..' must point to itself. */
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if (sc->ip == mp->m_rootip) {
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if (sc->ip->i_ino != mp->m_sb.sb_rootino ||
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sc->ip->i_ino != dnum)
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xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
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goto out;
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}
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do {
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error = xchk_parent_validate(sc, dnum, &try_again);
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if (error)
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goto out;
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} while (try_again && ++tries < 20);
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/*
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* We gave it our best shot but failed, so mark this scrub
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* incomplete. Userspace can decide if it wants to try again.
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*/
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if (try_again && tries == 20)
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xchk_set_incomplete(sc);
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out:
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/*
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* If we failed to lock the parent inode even after a retry, just mark
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* this scrub incomplete and return.
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*/
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if ((sc->flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
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error = 0;
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xchk_set_incomplete(sc);
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}
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return error;
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}
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