From 6b631c60c90a1e5264bc9bcdca2c0adb492d7a62 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Thu, 22 Feb 2024 12:31:00 -0800 Subject: [PATCH] xfs: teach repair to fix file nlinks Fix the file link counts since we just computed the correct ones. Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- fs/xfs/Makefile | 1 + fs/xfs/scrub/nlinks.c | 4 +- fs/xfs/scrub/nlinks.h | 5 +- fs/xfs/scrub/nlinks_repair.c | 223 +++++++++++++++++++++++++++++++++++ fs/xfs/scrub/repair.h | 2 + fs/xfs/scrub/scrub.c | 2 +- fs/xfs/scrub/trace.h | 3 + 7 files changed, 237 insertions(+), 3 deletions(-) create mode 100644 fs/xfs/scrub/nlinks_repair.c diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile index e53a26b58046..253744092915 100644 --- a/fs/xfs/Makefile +++ b/fs/xfs/Makefile @@ -194,6 +194,7 @@ xfs-y += $(addprefix scrub/, \ ialloc_repair.o \ inode_repair.o \ newbt.o \ + nlinks_repair.o \ reap.o \ refcount_repair.o \ repair.o \ diff --git a/fs/xfs/scrub/nlinks.c b/fs/xfs/scrub/nlinks.c index 341ab737f9c5..8a7d9557897c 100644 --- a/fs/xfs/scrub/nlinks.c +++ b/fs/xfs/scrub/nlinks.c @@ -61,7 +61,9 @@ xchk_setup_nlinks( * set the INCOMPLETE flag even when a negative errno is returned. This care * must be taken with certain errno values (i.e. EFSBADCRC, EFSCORRUPTED, * ECANCELED) that are absorbed into a scrub state flag update by - * xchk_*_process_error. + * xchk_*_process_error. Scrub and repair share the same incore data + * structures, so the INCOMPLETE flag is critical to prevent a repair based on + * insufficient information. * * Because we are scanning a live filesystem, it's possible that another thread * will try to update the link counts for an inode that we've already scanned. diff --git a/fs/xfs/scrub/nlinks.h b/fs/xfs/scrub/nlinks.h index ea6408e1c183..a950f3daf204 100644 --- a/fs/xfs/scrub/nlinks.h +++ b/fs/xfs/scrub/nlinks.h @@ -81,9 +81,12 @@ struct xchk_nlink { */ #define XCHK_NLINK_WRITTEN (1U << 0) -/* This data item was seen by the check-time compare function. */ +/* Already checked this link count record. */ #define XCHK_NLINK_COMPARE_SCANNED (1U << 1) +/* Already made a repair with this link count record. */ +#define XREP_NLINK_DIRTY (1U << 2) + /* Compute total link count, using large enough variables to detect overflow. */ static inline uint64_t xchk_nlink_total(struct xfs_inode *ip, const struct xchk_nlink *live) diff --git a/fs/xfs/scrub/nlinks_repair.c b/fs/xfs/scrub/nlinks_repair.c new file mode 100644 index 000000000000..b87618322f55 --- /dev/null +++ b/fs/xfs/scrub/nlinks_repair.c @@ -0,0 +1,223 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2021-2024 Oracle. All Rights Reserved. + * Author: Darrick J. Wong + */ +#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_trans.h" +#include "xfs_inode.h" +#include "xfs_icache.h" +#include "xfs_bmap_util.h" +#include "xfs_iwalk.h" +#include "xfs_ialloc.h" +#include "xfs_sb.h" +#include "scrub/scrub.h" +#include "scrub/common.h" +#include "scrub/repair.h" +#include "scrub/xfile.h" +#include "scrub/xfarray.h" +#include "scrub/iscan.h" +#include "scrub/nlinks.h" +#include "scrub/trace.h" + +/* + * Live Inode Link Count Repair + * ============================ + * + * Use the live inode link count information that we collected to replace the + * nlink values of the incore inodes. A scrub->repair cycle should have left + * the live data and hooks active, so this is safe so long as we make sure the + * inode is locked. + */ + +/* + * Correct the link count of the given inode. Because we have to grab locks + * and resources in a certain order, it's possible that this will be a no-op. + */ +STATIC int +xrep_nlinks_repair_inode( + struct xchk_nlink_ctrs *xnc) +{ + struct xchk_nlink obs; + struct xfs_scrub *sc = xnc->sc; + struct xfs_mount *mp = sc->mp; + struct xfs_inode *ip = sc->ip; + uint64_t total_links; + uint64_t actual_nlink; + bool dirty = false; + int error; + + xchk_ilock(sc, XFS_IOLOCK_EXCL); + + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_link, 0, 0, 0, &sc->tp); + if (error) + return error; + + xchk_ilock(sc, XFS_ILOCK_EXCL); + xfs_trans_ijoin(sc->tp, ip, 0); + + mutex_lock(&xnc->lock); + + if (xchk_iscan_aborted(&xnc->collect_iscan)) { + error = -ECANCELED; + goto out_scanlock; + } + + error = xfarray_load_sparse(xnc->nlinks, ip->i_ino, &obs); + if (error) + goto out_scanlock; + + /* + * We're done accessing the shared scan data, so we can drop the lock. + * We still hold @ip's ILOCK, so its link count cannot change. + */ + mutex_unlock(&xnc->lock); + + total_links = xchk_nlink_total(ip, &obs); + actual_nlink = VFS_I(ip)->i_nlink; + + /* + * Non-directories cannot have directories pointing up to them. + * + * We previously set error to zero, but set it again because one static + * checker author fears that programmers will fail to maintain this + * invariant and built their tool to flag this as a security risk. A + * different tool author made their bot complain about the redundant + * store. This is a never-ending and stupid battle; both tools missed + * *actual bugs* elsewhere; and I no longer care. + */ + if (!S_ISDIR(VFS_I(ip)->i_mode) && obs.children != 0) { + trace_xrep_nlinks_unfixable_inode(mp, ip, &obs); + error = 0; + goto out_trans; + } + + /* + * We did not find any links to this inode. If the inode agrees, we + * have nothing further to do. If not, the inode has a nonzero link + * count and we don't have anywhere to graft the child onto. Dropping + * a live inode's link count to zero can cause unexpected shutdowns in + * inactivation, so leave it alone. + */ + if (total_links == 0) { + if (actual_nlink != 0) + trace_xrep_nlinks_unfixable_inode(mp, ip, &obs); + goto out_trans; + } + + /* Commit the new link count if it changed. */ + if (total_links != actual_nlink) { + if (total_links > XFS_MAXLINK) { + trace_xrep_nlinks_unfixable_inode(mp, ip, &obs); + goto out_trans; + } + + trace_xrep_nlinks_update_inode(mp, ip, &obs); + + set_nlink(VFS_I(ip), total_links); + dirty = true; + } + + if (!dirty) { + error = 0; + goto out_trans; + } + + xfs_trans_log_inode(sc->tp, ip, XFS_ILOG_CORE); + + error = xrep_trans_commit(sc); + xchk_iunlock(sc, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL); + return error; + +out_scanlock: + mutex_unlock(&xnc->lock); +out_trans: + xchk_trans_cancel(sc); + xchk_iunlock(sc, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL); + return error; +} + +/* + * Try to visit every inode in the filesystem for repairs. Move on if we can't + * grab an inode, since we're still making forward progress. + */ +static int +xrep_nlinks_iter( + struct xchk_nlink_ctrs *xnc, + struct xfs_inode **ipp) +{ + int error; + + do { + error = xchk_iscan_iter(&xnc->compare_iscan, ipp); + } while (error == -EBUSY); + + return error; +} + +/* Commit the new inode link counters. */ +int +xrep_nlinks( + struct xfs_scrub *sc) +{ + struct xchk_nlink_ctrs *xnc = sc->buf; + int error; + + /* + * We need ftype for an accurate count of the number of child + * subdirectory links. Child subdirectories with a back link (dotdot + * entry) but no forward link are unfixable, so we cannot repair the + * link count of the parent directory based on the back link count + * alone. Filesystems without ftype support are rare (old V4) so we + * just skip out here. + */ + if (!xfs_has_ftype(sc->mp)) + return -EOPNOTSUPP; + + /* + * Use the inobt to walk all allocated inodes to compare and fix the + * link counts. Retry iget every tenth of a second for up to 30 + * seconds -- even if repair misses a few inodes, we still try to fix + * as many of them as we can. + */ + xchk_iscan_start(sc, 30000, 100, &xnc->compare_iscan); + ASSERT(sc->ip == NULL); + + while ((error = xrep_nlinks_iter(xnc, &sc->ip)) == 1) { + /* + * Commit the scrub transaction so that we can create repair + * transactions with the correct reservations. + */ + xchk_trans_cancel(sc); + + error = xrep_nlinks_repair_inode(xnc); + xchk_iscan_mark_visited(&xnc->compare_iscan, sc->ip); + xchk_irele(sc, sc->ip); + sc->ip = NULL; + if (error) + break; + + if (xchk_should_terminate(sc, &error)) + break; + + /* + * Create a new empty transaction so that we can advance the + * iscan cursor without deadlocking if the inobt has a cycle. + * We can only push the inactivation workqueues with an empty + * transaction. + */ + error = xchk_trans_alloc_empty(sc); + if (error) + break; + } + xchk_iscan_iter_finish(&xnc->compare_iscan); + xchk_iscan_teardown(&xnc->compare_iscan); + + return error; +} diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h index fdfa06699921..8edac0150e96 100644 --- a/fs/xfs/scrub/repair.h +++ b/fs/xfs/scrub/repair.h @@ -116,6 +116,7 @@ int xrep_inode(struct xfs_scrub *sc); int xrep_bmap_data(struct xfs_scrub *sc); int xrep_bmap_attr(struct xfs_scrub *sc); int xrep_bmap_cow(struct xfs_scrub *sc); +int xrep_nlinks(struct xfs_scrub *sc); #ifdef CONFIG_XFS_RT int xrep_rtbitmap(struct xfs_scrub *sc); @@ -196,6 +197,7 @@ xrep_setup_nothing( #define xrep_rtbitmap xrep_notsupported #define xrep_quota xrep_notsupported #define xrep_quotacheck xrep_notsupported +#define xrep_nlinks xrep_notsupported #endif /* CONFIG_XFS_ONLINE_REPAIR */ diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c index 883c47b6c686..c0b99184bb3e 100644 --- a/fs/xfs/scrub/scrub.c +++ b/fs/xfs/scrub/scrub.c @@ -376,7 +376,7 @@ static const struct xchk_meta_ops meta_scrub_ops[] = { .type = ST_FS, .setup = xchk_setup_nlinks, .scrub = xchk_nlinks, - .repair = xrep_notsupported, + .repair = xrep_nlinks, }, }; diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h index 9512170ea9a7..c9b6b0e0bf11 100644 --- a/fs/xfs/scrub/trace.h +++ b/fs/xfs/scrub/trace.h @@ -2185,6 +2185,9 @@ DEFINE_XREP_DQUOT_EVENT(xrep_dquot_item_fill_bmap_hole); DEFINE_XREP_DQUOT_EVENT(xrep_quotacheck_dquot); #endif /* CONFIG_XFS_QUOTA */ +DEFINE_SCRUB_NLINKS_DIFF_EVENT(xrep_nlinks_update_inode); +DEFINE_SCRUB_NLINKS_DIFF_EVENT(xrep_nlinks_unfixable_inode); + #endif /* IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR) */ #endif /* _TRACE_XFS_SCRUB_TRACE_H */