// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2017 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*/
#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_log_format.h"
#include "xfs_inode.h"
#include "xfs_icache.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
/* Set us up to scrub parents. */
int
xchk_setup_parent(
struct xfs_scrub *sc,
struct xfs_inode *ip)
{
return xchk_setup_inode_contents(sc, ip, 0);
}
/* Parent pointers */
/* Look for an entry in a parent pointing to this inode. */
struct xchk_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
xchk_parent_actor(
struct dir_context *dc,
const char *name,
int namelen,
loff_t pos,
u64 ino,
unsigned type)
{
struct xchk_parent_ctx *spc;
spc = container_of(dc, struct xchk_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
xchk_parent_count_parent_dentries(
struct xfs_scrub *sc,
struct xfs_inode *parent,
xfs_nlink_t *nlink)
{
struct xchk_parent_ctx spc = {
.dc.actor = xchk_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
xchk_parent_validate(
struct xfs_scrub *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 = 0;
*try_again = false;
if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
goto out;
/* '..' must not point to ourselves. */
if (sc->ip->i_ino == dnum) {
xchk_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.
*
* If _iget returns -EINVAL then the parent inode number is garbage
* and the directory is corrupt. If the _iget returns -EFSCORRUPTED
* or -EFSBADCRC then the parent is corrupt which is a cross
* referencing error. Any other error is an operational error.
*/
error = xfs_iget(mp, sc->tp, dnum, XFS_IGET_UNTRUSTED, 0, &dp);
if (error == -EINVAL) {
error = -EFSCORRUPTED;
xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error);
goto out;
}
if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
goto out;
if (dp == sc->ip || !S_ISDIR(VFS_I(dp)->i_mode)) {
xchk_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 = xchk_parent_count_parent_dentries(sc, dp, &nlink);
if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0,
&error))
goto out_unlock;
if (nlink != expected_nlink)
xchk_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;
error = xchk_ilock_inverted(dp, XFS_IOLOCK_SHARED);
if (error)
goto out_rele;
/* Go looking for our dentry. */
error = xchk_parent_count_parent_dentries(sc, dp, &nlink);
if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
goto out_unlock;
/* Drop the parent lock, relock this inode. */
xfs_iunlock(dp, XFS_IOLOCK_SHARED);
error = xchk_ilock_inverted(sc->ip, XFS_IOLOCK_EXCL);
if (error)
goto out_rele;
sc->ilock_flags = XFS_IOLOCK_EXCL;
/*
* 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 (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
goto out_rele;
/* Drat, parent changed. Try again! */
if (dnum != dp->i_ino) {
xfs_irele(dp);
*try_again = true;
return 0;
}
xfs_irele(dp);
/*
* '..' didn't change, so check that there was only one entry
* for us in the parent.
*/
if (nlink != expected_nlink)
xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
return error;
out_unlock:
xfs_iunlock(dp, XFS_IOLOCK_SHARED);
out_rele:
xfs_irele(dp);
out:
return error;
}
/* Scrub a parent pointer. */
int
xchk_parent(
struct xfs_scrub *sc)
{
struct xfs_mount *mp = sc->mp;
xfs_ino_t dnum;
bool try_again;
int tries = 0;
int error = 0;
/*
* 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)) {
xchk_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 (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
goto out;
if (!xfs_verify_dir_ino(mp, dnum)) {
xchk_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)
xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
goto out;
}
do {
error = xchk_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)
xchk_set_incomplete(sc);
out:
/*
* If we failed to lock the parent inode even after a retry, just mark
* this scrub incomplete and return.
*/
if ((sc->flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
error = 0;
xchk_set_incomplete(sc);
}
return error;
}