diff options
author | Darrick J. Wong <djwong@kernel.org> | 2022-07-14 11:06:58 -0700 |
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committer | Darrick J. Wong <djwong@kernel.org> | 2022-10-14 14:16:56 -0700 |
commit | cdff922babd46994d6e70672c78a33e6c9e9be4b (patch) | |
tree | 761babc1187c972d6e076f5fb3a2ed88c78abbdd /fs/xfs/scrub/symlink_repair.c | |
parent | 9678c9e283f964c7b8dddd1c3933b7f01dc8701e (diff) |
xfs: online repair of symbolic linksrepair-symlink_2022-10-14
If a symbolic link target looks bad, try to sift through the rubble to
find as much of the target buffer that we can, and stage a new target
(short or remote format as needed) in a temporary file and use the
atomic extent swapping mechanism to commit the results.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Diffstat (limited to 'fs/xfs/scrub/symlink_repair.c')
-rw-r--r-- | fs/xfs/scrub/symlink_repair.c | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/fs/xfs/scrub/symlink_repair.c b/fs/xfs/scrub/symlink_repair.c new file mode 100644 index 000000000000..0bf9d027be41 --- /dev/null +++ b/fs/xfs/scrub/symlink_repair.c @@ -0,0 +1,456 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2022 Oracle. All Rights Reserved. + * Author: Darrick J. Wong <djwong@kernel.org> + */ +#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_inode_fork.h" +#include "xfs_symlink.h" +#include "xfs_bmap.h" +#include "xfs_quota.h" +#include "xfs_da_format.h" +#include "xfs_da_btree.h" +#include "xfs_bmap_btree.h" +#include "xfs_trans_space.h" +#include "xfs_symlink_remote.h" +#include "xfs_swapext.h" +#include "xfs_xchgrange.h" +#include "scrub/xfs_scrub.h" +#include "scrub/scrub.h" +#include "scrub/common.h" +#include "scrub/trace.h" +#include "scrub/repair.h" +#include "scrub/tempfile.h" +#include "scrub/tempswap.h" +#include "scrub/reap.h" + +/* + * Symbolic Link Repair + * ==================== + * + * We repair symbolic links by reading whatever target data we can find, up to + * the first NULL byte. Zero length symlinks are turned into links to the + * current directory. The new target is written into a private hidden + * temporary file, and then an atomic extent swap commits the new symlink + * target to the file being repaired. + */ + +/* Set us up to repair the rtsummary file. */ +int +xrep_setup_symlink( + struct xfs_scrub *sc, + unsigned int *resblks) +{ + struct xfs_mount *mp = sc->mp; + unsigned long long blocks; + int error; + + error = xrep_tempfile_create(sc, S_IFLNK); + if (error) + return error; + + /* + * If we're doing a repair, we reserve enough blocks to write out a + * completely new symlink file, plus twice as many blocks as we would + * need if we can only allocate one block per data fork mapping. This + * should cover the preallocation of the temporary file and swapping + * the extent mappings. + * + * We cannot use xfs_swapext_estimate because we have not yet + * constructed the replacement rtsummary and therefore do not know how + * many extents it will use. By the time we do, we will have a dirty + * transaction (which we cannot drop because we cannot drop the + * rtsummary ILOCK) and cannot ask for more reservation. + */ + blocks = xfs_symlink_blocks(sc->mp, XFS_SYMLINK_MAXLEN); + blocks += xfs_bmbt_calc_size(mp, blocks) * 2; + if (blocks > UINT_MAX) + return -EOPNOTSUPP; + + *resblks += blocks; + return 0; +} + +/* Try to salvage the pathname from rmt blocks. */ +STATIC int +xrep_symlink_salvage_remote( + struct xfs_scrub *sc) +{ + struct xfs_bmbt_irec mval[XFS_SYMLINK_MAPS]; + struct xfs_inode *ip = sc->ip; + struct xfs_buf *bp; + char *target_buf = sc->buf; + xfs_failaddr_t fa; + xfs_filblks_t fsblocks; + xfs_daddr_t d; + loff_t len; + loff_t offset; + unsigned int byte_cnt; + bool magic_ok; + bool hdr_ok; + int n; + int nmaps = XFS_SYMLINK_MAPS; + int error; + + /* We'll only read until the buffer is full. */ + len = min_t(loff_t, ip->i_disk_size, XFS_SYMLINK_MAXLEN); + fsblocks = xfs_symlink_blocks(sc->mp, len); + error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0); + if (error) + return error; + + offset = 0; + for (n = 0; n < nmaps; n++) { + struct xfs_dsymlink_hdr *dsl; + + d = XFS_FSB_TO_DADDR(sc->mp, mval[n].br_startblock); + + /* Read the rmt block. We'll run the verifiers manually. */ + error = xfs_trans_read_buf(sc->mp, sc->tp, sc->mp->m_ddev_targp, + d, XFS_FSB_TO_BB(sc->mp, mval[n].br_blockcount), + 0, &bp, NULL); + if (error) + return error; + bp->b_ops = &xfs_symlink_buf_ops; + + /* How many bytes do we expect to get out of this buffer? */ + byte_cnt = XFS_FSB_TO_B(sc->mp, mval[n].br_blockcount); + byte_cnt = XFS_SYMLINK_BUF_SPACE(sc->mp, byte_cnt); + byte_cnt = min_t(unsigned int, byte_cnt, len); + + /* + * See if the verifiers accept this block. We're willing to + * salvage if the if the offset/byte/ino are ok and either the + * verifier passed or the magic is ok. Anything else and we + * stop dead in our tracks. + */ + fa = bp->b_ops->verify_struct(bp); + dsl = bp->b_addr; + magic_ok = dsl->sl_magic == cpu_to_be32(XFS_SYMLINK_MAGIC); + hdr_ok = xfs_symlink_hdr_ok(ip->i_ino, offset, byte_cnt, bp); + if (!hdr_ok || (fa != NULL && !magic_ok)) + break; + + memcpy(target_buf + offset, dsl + 1, byte_cnt); + + len -= byte_cnt; + offset += byte_cnt; + } + + /* Ensure we have a zero at the end, and /some/ contents. */ + if (offset == 0 || target_buf[0] == 0) + sprintf(target_buf, "."); + else + target_buf[offset] = 0; + return 0; +} + +/* + * Try to salvage an inline symlink's contents. Empty symlinks become a link + * to the current directory. + */ +STATIC void +xrep_symlink_salvage_inline( + struct xfs_scrub *sc) +{ + struct xfs_inode *ip = sc->ip; + char *target_buf = sc->buf; + struct xfs_ifork *ifp; + + ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK); + if (ifp->if_u1.if_data) + strncpy(target_buf, ifp->if_u1.if_data, xfs_inode_data_fork_size(ip)); + if (target_buf[0] == 0) + sprintf(target_buf, "."); +} + +/* Salvage whatever we can of the target. */ +STATIC int +xrep_symlink_salvage( + struct xfs_scrub *sc) +{ + if (sc->ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) { + xrep_symlink_salvage_inline(sc); + } else { + int error = xrep_symlink_salvage_remote(sc); + + if (error) + return error; + } + + trace_xrep_symlink_salvage_target(sc->ip, sc->buf, strlen(sc->buf)); + return 0; +} + +STATIC void +xrep_symlink_local_to_remote( + struct xfs_trans *tp, + struct xfs_buf *bp, + struct xfs_inode *ip, + struct xfs_ifork *ifp, + void *priv) +{ + struct xfs_scrub *sc = priv; + struct xfs_dsymlink_hdr *dsl = bp->b_addr; + + xfs_symlink_local_to_remote(tp, bp, ip, ifp, NULL); + + if (!xfs_has_crc(sc->mp)) + return; + + dsl->sl_owner = cpu_to_be64(sc->ip->i_ino); + xfs_trans_log_buf(tp, bp, 0, sizeof(struct xfs_dsymlink_hdr) + + ifp->if_bytes - 1); +} + +/* + * Prepare both links' data forks for extent swapping. Promote the tempfile + * from local format to extents format, and if the file being repaired has a + * short format data fork, turn it into an empty extent list. + */ +STATIC int +xrep_symlink_swap_prep( + struct xfs_scrub *sc, + bool temp_local, + bool ip_local) +{ + int error; + + /* + * If the temp link is in shortform format, convert that to a remote + * target so that we can use the atomic extent swap. + */ + if (temp_local) { + int logflags = XFS_ILOG_CORE; + + error = xfs_bmap_local_to_extents(sc->tp, sc->tempip, 1, + &logflags, XFS_DATA_FORK, + xrep_symlink_local_to_remote, + sc); + if (error) + return error; + + xfs_trans_log_inode(sc->tp, sc->ip, 0); + + error = xfs_defer_finish(&sc->tp); + if (error) + return error; + } + + /* + * If the file being repaired had a shortform data fork, convert that + * to an empty extent list in preparation for the atomic extent swap. + */ + if (ip_local) { + struct xfs_ifork *ifp; + + ifp = xfs_ifork_ptr(sc->ip, XFS_DATA_FORK); + xfs_idestroy_fork(ifp); + ifp->if_format = XFS_DINODE_FMT_EXTENTS; + ifp->if_nextents = 0; + ifp->if_bytes = 0; + ifp->if_u1.if_root = NULL; + ifp->if_height = 0; + + xfs_trans_log_inode(sc->tp, sc->ip, + XFS_ILOG_CORE | XFS_ILOG_DDATA); + } + + return 0; +} + +/* Swap the temporary link's data fork with the one being repaired. */ +STATIC int +xrep_symlink_swap( + struct xfs_scrub *sc) +{ + struct xrep_tempswap *tx = sc->buf; + bool ip_local, temp_local; + int error; + + /* + * We're done with the temporary buffer, so we can reuse it for the + * tempfile swap information. + */ + error = xrep_tempswap_trans_alloc(sc, XFS_DATA_FORK, tx); + if (error) + return error; + + ip_local = sc->ip->i_df.if_format == XFS_DINODE_FMT_LOCAL; + temp_local = sc->tempip->i_df.if_format == XFS_DINODE_FMT_LOCAL; + + /* + * If the both links have a local format data fork and the rebuilt + * remote data would fit in the repaired file's data fork, copy the + * contents from the tempfile and declare ourselves done. + */ + if (ip_local && temp_local && + sc->tempip->i_disk_size <= xfs_inode_data_fork_size(sc->ip)) { + xrep_tempfile_copyout_local(sc, XFS_DATA_FORK); + return 0; + } + + /* Otherwise, make sure both data forks are in block-mapping mode. */ + error = xrep_symlink_swap_prep(sc, temp_local, ip_local); + if (error) + return error; + + return xrep_tempswap_contents(sc, tx); +} + +/* + * Free all the remote blocks and reset the data fork. The caller must join + * the inode to the transaction. This function returns with the inode joined + * to a clean scrub transaction. + */ +STATIC int +xrep_symlink_reset_fork( + struct xfs_scrub *sc) +{ + struct xfs_ifork *ifp = xfs_ifork_ptr(sc->tempip, XFS_DATA_FORK); + int error; + + /* Unmap all the remote target buffers. */ + if (xfs_ifork_has_extents(ifp)) { + error = xrep_reap_ifork(sc, sc->tempip, XFS_DATA_FORK); + if (error) + return error; + } + + trace_xrep_symlink_reset_fork(sc->tempip); + + /* Reset the temp link to have the same dummy content. */ + xfs_idestroy_fork(ifp); + error = xfs_symlink_write_target(sc->tp, sc->tempip, ".", 1, 0, 0); + if (error) + return error; + + return xrep_tempfile_roll_trans(sc); +} + +/* + * Reinitialize a link target. Caller must ensure the inode is joined to + * the transaction. + */ +STATIC int +xrep_symlink_rebuild( + struct xfs_scrub *sc) +{ + char *target_buf = sc->buf; + xfs_fsblock_t fs_blocks; + unsigned int target_len; + unsigned int resblks; + int error; + + /* How many blocks do we need? */ + target_len = strlen(target_buf); + ASSERT(target_len != 0); + if (target_len == 0 || target_len > XFS_SYMLINK_MAXLEN) + return -EFSCORRUPTED; + + trace_xrep_symlink_rebuild(sc->ip); + + /* + * In preparation to write the new symlink target to the temporary + * file, drop the ILOCK of the file being repaired (it shouldn't be + * joined) and take the ILOCK of the temporary file. + * + * The VFS does not take the IOLOCK while reading a symlink (and new + * symlinks are hidden with INEW until they've been written) so it's + * possible that a readlink() could see the old corrupted contents + * while we're doing this. + */ + xchk_iunlock(sc, XFS_ILOCK_EXCL); + xrep_tempfile_ilock(sc); + xfs_trans_ijoin(sc->tp, sc->tempip, 0); + + /* + * Reserve resources to reinitialize the target. We're allowed to + * exceed file quota to repair inconsistent metadata, though this is + * unlikely. + */ + fs_blocks = xfs_symlink_blocks(sc->mp, target_len); + resblks = XFS_SYMLINK_SPACE_RES(sc->mp, target_len, fs_blocks); + error = xfs_trans_reserve_quota_nblks(sc->tp, sc->tempip, resblks, 0, + true); + if (error) + return error; + + /* Erase the dummy target set up by the tempfile initialization. */ + xfs_idestroy_fork(&sc->tempip->i_df); + sc->tempip->i_df.if_bytes = 0; + sc->tempip->i_df.if_format = XFS_DINODE_FMT_EXTENTS; + + /* Write the salvaged target to the temporary link. */ + error = __xfs_symlink_write_target(sc->tp, sc->tempip, sc->ip->i_ino, + target_buf, target_len, fs_blocks, resblks); + if (error) + return error; + + /* + * Commit the repair transaction so that we can use the atomic extent + * swap helper functions to compute the correct block reservations and + * re-lock the inodes. + */ + error = xrep_trans_commit(sc); + if (error) + return error; + + /* Last chance to abort before we start committing fixes. */ + if (xchk_should_terminate(sc, &error)) + return error; + + xrep_tempfile_iunlock(sc); + + /* + * Swap the temp link's data fork with the file being repaired. This + * recreates the transaction and takes the ILOCKs of the file being + * repaired and the temporary file. + */ + error = xrep_symlink_swap(sc); + if (error) + return error; + + /* + * Release the old symlink blocks and reset the data fork of the temp + * link to an empty shortform link. + */ + return xrep_symlink_reset_fork(sc); +} + +/* Repair a symbolic link. */ +int +xrep_symlink( + struct xfs_scrub *sc) +{ + int error; + + /* We require the rmapbt to rebuild anything. */ + if (!xfs_has_rmapbt(sc->mp)) + return -EOPNOTSUPP; + + error = xfs_qm_dqattach_locked(sc->ip, false); + if (error) + return error; + + ASSERT(sc->ilock_flags & XFS_ILOCK_EXCL); + + error = xrep_symlink_salvage(sc); + if (error) + return error; + + /* Now reset the target. */ + return xrep_symlink_rebuild(sc); +} |