On Sun, Jun 24, 2018 at 12:25:16PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Repair inconsistent symbolic link data.
.....
> +/*
> + * Symbolic Link Repair
> + * ====================
> + *
> + * There's not much we can do to repair symbolic links -- we truncate them to
> + * the first NULL byte and fix up the remote target block headers if they're
> + * incorrect. Zero-length symlinks are turned into links to /.
> + */
> +
> +/* Blow out the whole symlink; replace contents. */
> +STATIC int
> +xfs_repair_symlink_rewrite(
> + struct xfs_trans **tpp,
> + struct xfs_inode *ip,
> + const char *target_path,
> + int pathlen)
> +{
> + struct xfs_defer_ops dfops;
> + struct xfs_bmbt_irec mval[XFS_SYMLINK_MAPS];
> + struct xfs_ifork *ifp;
> + const char *cur_chunk;
> + struct xfs_mount *mp = (*tpp)->t_mountp;
> + struct xfs_buf *bp;
> + xfs_fsblock_t first_block;
> + xfs_fileoff_t first_fsb;
> + xfs_filblks_t fs_blocks;
> + xfs_daddr_t d;
> + int byte_cnt;
> + int n;
> + int nmaps;
> + int offset;
> + int error = 0;
> +
> + ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> +
> + /* Truncate the whole data fork if it wasn't inline. */
> + if (!(ifp->if_flags & XFS_IFINLINE)) {
> + error = xfs_itruncate_extents(tpp, ip, XFS_DATA_FORK, 0);
> + if (error)
> + goto out;
> + }
> +
> + /* Blow out the in-core fork and zero the on-disk fork. */
> + xfs_idestroy_fork(ip, XFS_DATA_FORK);
> + ip->i_d.di_format = XFS_DINODE_FMT_EXTENTS;
> + ip->i_d.di_nextents = 0;
> + memset(&ip->i_df, 0, sizeof(struct xfs_ifork));
> + ip->i_df.if_flags |= XFS_IFEXTENTS;
This looks familiar - doesn't the fork zapping code do exactly this,
too? factor into a helper?
> +
> + /* Rewrite an inline symlink. */
> + if (pathlen <= XFS_IFORK_DSIZE(ip)) {
> + xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
> +
> + i_size_write(VFS_I(ip), pathlen);
> + ip->i_d.di_size = pathlen;
> + ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
> + xfs_trans_log_inode(*tpp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
> + goto out;
> +
> + }
Might make sense to separate inline vs remote into separate
functions - we tend to do that everywhere else in the symlink code.
> +
> + /* Rewrite a remote symlink. */
> + fs_blocks = xfs_symlink_blocks(mp, pathlen);
> + first_fsb = 0;
> + nmaps = XFS_SYMLINK_MAPS;
> +
> + /* Reserve quota for new blocks. */
> + error = xfs_trans_reserve_quota_nblks(*tpp, ip, fs_blocks, 0,
> + XFS_QMOPT_RES_REGBLKS);
> + if (error)
> + goto out;
> +
> + /* Map blocks, write symlink target. */
> + xfs_defer_init(&dfops, &first_block);
> +
> + error = xfs_bmapi_write(*tpp, ip, first_fsb, fs_blocks,
> + XFS_BMAPI_METADATA, &first_block, fs_blocks,
> + mval, &nmaps, &dfops);
> + if (error)
> + goto out_bmap_cancel;
> +
> + ip->i_d.di_size = pathlen;
> + i_size_write(VFS_I(ip), pathlen);
> + xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
> +
> + cur_chunk = target_path;
> + offset = 0;
> + for (n = 0; n < nmaps; n++) {
> + char *buf;
> +
> + d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
> + byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
> + bp = xfs_trans_get_buf(*tpp, mp->m_ddev_targp, d,
> + BTOBB(byte_cnt), 0);
> + if (!bp) {
> + error = -ENOMEM;
> + goto out_bmap_cancel;
> + }
> + bp->b_ops = &xfs_symlink_buf_ops;
> +
> + byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
> + byte_cnt = min(byte_cnt, pathlen);
> +
> + buf = bp->b_addr;
> + buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
> + byte_cnt, bp);
> +
> + memcpy(buf, cur_chunk, byte_cnt);
> +
> + cur_chunk += byte_cnt;
> + pathlen -= byte_cnt;
> + offset += byte_cnt;
> +
> + xfs_trans_buf_set_type(*tpp, bp, XFS_BLFT_SYMLINK_BUF);
> + xfs_trans_log_buf(*tpp, bp, 0, (buf + byte_cnt - 1) -
> + (char *)bp->b_addr);
> + }
> + ASSERT(pathlen == 0);
This just looks like a copynpaste of main loop in xfs_symlink() -
can you factor that into a helper, please?
> +
> + error = xfs_defer_finish(tpp, &dfops);
> + if (error)
> + goto out_bmap_cancel;
> +
> + return 0;
> +
> +out_bmap_cancel:
> + xfs_defer_cancel(&dfops);
> +out:
> + return error;
> +}
> +
> +/* Fix everything that fails the verifiers in the remote blocks. */
> +STATIC int
> +xfs_repair_symlink_fix_remotes(
> + struct xfs_scrub_context *sc,
> + loff_t len)
> +{
> + struct xfs_bmbt_irec mval[XFS_SYMLINK_MAPS];
> + struct xfs_buf *bp;
> + xfs_filblks_t fsblocks;
> + xfs_daddr_t d;
> + loff_t offset;
> + unsigned int byte_cnt;
> + int n;
> + int nmaps = XFS_SYMLINK_MAPS;
> + int nr;
> + int error;
> +
> + fsblocks = xfs_symlink_blocks(sc->mp, len);
> + error = xfs_bmapi_read(sc->ip, 0, fsblocks, mval, &nmaps, 0);
> + if (error)
> + return error;
> +
> + offset = 0;
> + for (n = 0; n < nmaps; n++) {
> + d = XFS_FSB_TO_DADDR(sc->mp, mval[n].br_startblock);
> + byte_cnt = XFS_FSB_TO_B(sc->mp, mval[n].br_blockcount);
> +
> + error = xfs_trans_read_buf(sc->mp, sc->tp, sc->mp->m_ddev_targp,
> + d, BTOBB(byte_cnt), 0, &bp, NULL);
> + if (error)
> + return error;
> + bp->b_ops = &xfs_symlink_buf_ops;
> +
> + byte_cnt = XFS_SYMLINK_BUF_SPACE(sc->mp, byte_cnt);
> + if (len < byte_cnt)
> + byte_cnt = len;
can we make this the same as the other functions? i.e.
byte_cnt = min(byte_cnt, len);
> +
> + nr = xfs_symlink_hdr_set(sc->mp, sc->ip->i_ino, offset,
> + byte_cnt, bp);
> +
> + len -= byte_cnt;
> + offset += byte_cnt;
> +
> + xfs_trans_buf_set_type(sc->tp, bp, XFS_BLFT_SYMLINK_BUF);
> + xfs_trans_log_buf(sc->tp, bp, 0, nr - 1);
> + xfs_trans_brelse(sc->tp, bp);
xfs_trans_brelse() is a no-op here because the buffer has been
logged. It can be removed.
> + }
> + if (len != 0)
> + return -EFSCORRUPTED;
> +
> + return 0;
> +}
> +
> +/* Fix this inline symlink. */
> +STATIC int
> +xfs_repair_symlink_inline(
> + struct xfs_scrub_context *sc)
> +{
> + struct xfs_inode *ip = sc->ip;
> + struct xfs_ifork *ifp;
> + loff_t len;
> + size_t newlen;
> +
> + ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> + len = i_size_read(VFS_I(ip));
> + xfs_trans_ijoin(sc->tp, ip, 0);
> +
> + if (ifp->if_u1.if_data) {
> + newlen = strnlen(ifp->if_u1.if_data, XFS_IFORK_DSIZE(ip));
> + } else {
> + /* Zero length symlink becomes a root symlink. */
> + ifp->if_u1.if_data = kmem_alloc(4, KM_SLEEP);
> + snprintf(ifp->if_u1.if_data, 4, "/");
> + newlen = 1;
helper function shared with the fork zapping code?
> + }
> +
> + if (len > newlen) {
shouldn't this be 'if (len != newlen) {' ?
> + i_size_write(VFS_I(ip), newlen);
> + ip->i_d.di_size = newlen;
> + xfs_trans_log_inode(sc->tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
> + }
> +
> + return 0;
> +}
> +
> +/* Repair a remote symlink. */
> +STATIC int
> +xfs_repair_symlink_remote(
> + struct xfs_scrub_context *sc)
> +{
> + struct xfs_inode *ip = sc->ip;
> + loff_t len;
> + size_t newlen;
> + int error = 0;
> +
> + len = i_size_read(VFS_I(ip));
> + xfs_trans_ijoin(sc->tp, ip, 0);
> +
> + error = xfs_repair_symlink_fix_remotes(sc, len);
> + if (error)
> + return error;
> +
> + /* Roll transaction, release buffers. */
> + error = xfs_trans_roll_inode(&sc->tp, ip);
> + if (error)
> + return error;
> +
> + /* Size set correctly? */
> + len = i_size_read(VFS_I(ip));
> + xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + error = xfs_readlink(ip, sc->buf);
> + xfs_ilock(ip, XFS_ILOCK_EXCL);
Can we pass a "need_lock" flag to xfs_readlink() rather than
creating a race condition with anything that might be blocked on the
ilock waiting for repair to complete?
> + if (error)
> + return error;
> +
> + /*
> + * Figure out the new target length. We can't handle zero-length
> + * symlinks, so make sure that we don't write that out.
> + */
> + newlen = strnlen(sc->buf, XFS_SYMLINK_MAXLEN);
> + if (newlen == 0) {
> + *((char *)sc->buf) = '/';
> + newlen = 1;
We really need to do set the name of the repaired path for zero
length symlinks in only one place. It really seems to me that it
should done in xfs_repair_symlink_rewrite() if newlen is 0, not
here.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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