WSL2-Linux-Kernel/fs/xfs/scrub/parent.c

318 строки
8.6 KiB
C
Исходник Обычный вид История

/*
* 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 = 0;
*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 = 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)) {
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;
}