[PATCH 1/3] xfs: move orphan files to the orphanage

Darrick J. Wong
2023-12-31T20:38:20Z

When we're repairing a directory structure or fixing the dotdot entry of
a subdirectory, it's possible that we won't ever find a parent for the
subdirectory. When this is the case, move it to the orphanage, aka
/lost+found.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
.../filesystems/xfs-online-fsck-design.rst | 19 +
fs/xfs/Makefile | 1
fs/xfs/scrub/dir_repair.c | 130 +++++
fs/xfs/scrub/orphanage.c | 499 ++++++++++++++++++++
fs/xfs/scrub/orphanage.h | 75 +++
fs/xfs/scrub/parent_repair.c | 98 ++++
fs/xfs/scrub/scrub.c | 2
fs/xfs/scrub/scrub.h | 4
fs/xfs/scrub/trace.h | 28 +
fs/xfs/xfs_inode.c | 6
fs/xfs/xfs_inode.h | 1
11 files changed, 843 insertions(+), 20 deletions(-)
create mode 100644 fs/xfs/scrub/orphanage.c
create mode 100644 fs/xfs/scrub/orphanage.h

diff --git a/Documentation/filesystems/xfs-online-fsck-design.rst b/Documentation/filesystems/xfs-online-fsck-design.rst
index a0678101a7d02..63c78e1e85e52 100644
--- a/Documentation/filesystems/xfs-online-fsck-design.rst
+++ b/Documentation/filesystems/xfs-online-fsck-design.rst
@@ -4777,14 +4777,21 @@ Orphaned files are adopted by the orphanage as follows:
The ``xrep_orphanage_iolock_two`` function follows the inode locking
strategy discussed earlier.

-3. Call ``xrep_orphanage_compute_blkres`` and ``xrep_orphanage_compute_name``
- to compute the new name in the orphanage and the block reservation required.
-
-4. Use ``xrep_orphanage_adoption_prep`` to reserve resources to the repair
+3. Use ``xrep_adoption_trans_alloc`` to reserve resources to the repair
transaction.

-5. Call ``xrep_orphanage_adopt`` to reparent the orphaned file into the lost
- and found, and update the kernel dentry cache.
+4. Call ``xrep_orphanage_compute_name`` to compute the new name in the
+ orphanage.
+
+5. If the adoption is going to happen, call ``xrep_adoption_reparent`` to
+ reparent the orphaned file into the lost and found and invalidate the dentry
+ cache.
+
+6. Call ``xrep_adoption_finish`` to commit any filesystem updates, release the
+ orphanage ILOCK, and clean the scrub transaction.
+
+7. If a runtime error happens, call ``xrep_adoption_cancel`` to release all
+ resources.

The proposed patches are in the
`orphanage adoption
diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index 36e4cbbe21999..49f12fb8480e1 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -205,6 +205,7 @@ xfs-y += $(addprefix scrub/, \
inode_repair.o \
newbt.o \
nlinks_repair.o \
+ orphanage.o \
parent_repair.o \
rcbag_btree.o \
rcbag.o \
diff --git a/fs/xfs/scrub/dir_repair.c b/fs/xfs/scrub/dir_repair.c
index b22fd59c2f8b3..141682e2477af 100644
--- a/fs/xfs/scrub/dir_repair.c
+++ b/fs/xfs/scrub/dir_repair.c
@@ -42,6 +42,7 @@
#include "scrub/readdir.h"
#include "scrub/reap.h"
#include "scrub/findparent.h"
+#include "scrub/orphanage.h"

/*
* Directory Repair
@@ -115,12 +116,21 @@ struct xrep_dir {
*/
struct xrep_parent_scan_info pscan;

+ /*
+ * Context information for attaching this directory to the lost+found
+ * if this directory does not have a parent.
+ */
+ struct xrep_adoption adoption;
+
/* How many subdirectories did we find? */
uint64_t subdirs;

/* How many dirents did we find? */
unsigned int dirents;

+ /* Should we move this directory to the orphanage? */
+ bool needs_adoption;
+
/* Directory entry name, plus the trailing null. */
unsigned char namebuf[MAXNAMELEN];
};
@@ -147,6 +157,10 @@ xrep_setup_directory(

xchk_fsgates_enable(sc, XCHK_FSGATES_DIRENTS);

+ error = xrep_orphanage_try_create(sc);
+ if (error)
+ return error;
+
error = xrep_tempfile_create(sc, S_IFDIR);
if (error)
return error;
@@ -1137,10 +1151,8 @@ xrep_dir_set_nlink(
/*
* The directory is not on the incore unlinked list, which means that
* it needs to be reachable via the directory tree. Update the nlink
- * with our observed link count.
- *
- * XXX: A subsequent patch will handle parentless directories by moving
- * them to the lost and found instead of aborting the repair.
+ * with our observed link count. If the directory has no parent, it
+ * will be moved to the orphanage.
*/
if (!xfs_inode_on_unlinked_list(dp))
goto reset_nlink;
@@ -1151,6 +1163,7 @@ xrep_dir_set_nlink(
* inactivate when the last reference drops.
*/
if (rd->dirents == 0) {
+ rd->needs_adoption = false;
new_nlink = 0;
goto reset_nlink;
}
@@ -1159,7 +1172,8 @@ xrep_dir_set_nlink(
* The directory is on the unlinked list and we found dirents. This
* directory needs to be reachable via the directory tree. Remove the
* dir from the unlinked list and update nlink with the observed link
- * count.
+ * count. If the directory has no parent, it will be moved to the
+ * orphanage.
*/
pag = xfs_perag_get(sc->mp, XFS_INO_TO_AGNO(sc->mp, dp->i_ino));
if (!pag) {
@@ -1195,12 +1209,16 @@ xrep_dir_swap(
return -EFSCORRUPTED;

/*
- * If we never found the parent for this directory, we can't fix this
- * directory.
+ * If we never found the parent for this directory, temporarily assign
+ * the root dir as the parent; we'll move this to the orphanage after
+ * swapping the dir contents. We hold the ILOCK of the dir being
+ * repaired, so we're not worried about racy updates of dotdot.
*/
ASSERT(sc->ilock_flags & XFS_ILOCK_EXCL);
- if (rd->pscan.parent_ino == NULLFSINO)
- return -EFSCORRUPTED;
+ if (rd->pscan.parent_ino == NULLFSINO) {
+ rd->needs_adoption = true;
+ rd->pscan.parent_ino = rd->sc->mp->m_sb.sb_rootino;
+ }

/*
* Reset the temporary directory's '..' entry to point to the parent
@@ -1355,6 +1373,91 @@ xrep_dir_setup_scan(
return error;
}

+/*
+ * Move the current file to the orphanage.
+ *
+ * Caller must hold IOLOCK_EXCL on @sc->ip, and no other inode locks. Upon
+ * successful return, the scrub transaction will have enough extra reservation
+ * to make the move; it will hold IOLOCK_EXCL and ILOCK_EXCL of @sc->ip and the
+ * orphanage; and both inodes will be ijoined.
+ */
+STATIC int
+xrep_dir_move_to_orphanage(
+ struct xrep_dir *rd)
+{
+ struct xfs_scrub *sc = rd->sc;
+ xfs_ino_t orig_parent, new_parent;
+ int error;
+
+ /*
+ * We are about to drop the ILOCK on sc->ip to lock the orphanage and
+ * prepare for the adoption. Therefore, look up the old dotdot entry
+ * for sc->ip so that we can compare it after we re-lock sc->ip.
+ */
+ error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &orig_parent);
+ if (error)
+ return error;
+
+ /*
+ * Drop the ILOCK on the scrub target and commit the transaction.
+ * Adoption computes its own resource requirements and gathers the
+ * necessary components.
+ */
+ error = xrep_trans_commit(sc);
+ if (error)
+ return error;
+ xchk_iunlock(sc, XFS_ILOCK_EXCL);
+
+ /* If we can take the orphanage's iolock then we're ready to move. */
+ if (!xrep_orphanage_ilock_nowait(sc, XFS_IOLOCK_EXCL)) {
+ xchk_iunlock(sc, sc->ilock_flags);
+ error = xrep_orphanage_iolock_two(sc);
+ if (error)
+ return error;
+ }
+
+ /* Grab transaction and ILOCK the two files. */
+ error = xrep_adoption_trans_alloc(sc, &rd->adoption);
+ if (error)
+ return error;
+
+ error = xrep_adoption_compute_name(&rd->adoption, rd->namebuf);
+ if (error)
+ return error;
+
+ /*
+ * Now that we've reacquired the ILOCK on sc->ip, look up the dotdot
+ * entry again. If the parent changed or the child was unlinked while
+ * the child directory was unlocked, we don't need to move the child to
+ * the orphanage after all.
+ */
+ error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &new_parent);
+ if (error)
+ return error;
+
+ /*
+ * Attach to the orphanage if we still have a linked directory and it
+ * hasn't been moved.
+ */
+ if (orig_parent == new_parent && VFS_I(sc->ip)->i_nlink > 0) {
+ error = xrep_adoption_move(&rd->adoption);
+ if (error)
+ return error;
+ }
+
+ /*
+ * Launder the scrub transaction so we can drop the orphanage ILOCK
+ * and IOLOCK. Return holding the scrub target's ILOCK and IOLOCK.
+ */
+ error = xrep_adoption_trans_roll(&rd->adoption);
+ if (error)
+ return error;
+
+ xrep_orphanage_iunlock(sc, XFS_ILOCK_EXCL);
+ xrep_orphanage_iunlock(sc, XFS_IOLOCK_EXCL);
+ return 0;
+}
+
/*
* Repair the directory metadata.
*
@@ -1393,6 +1496,15 @@ xrep_directory(
if (error)
goto out_teardown;

+ if (rd->needs_adoption) {
+ if (!xrep_orphanage_can_adopt(rd->sc))
+ error = -EFSCORRUPTED;
+ else
+ error = xrep_dir_move_to_orphanage(rd);
+ if (error)
+ goto out_teardown;
+ }
+
out_teardown:
xrep_dir_teardown(sc);
return error;
diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
new file mode 100644
index 0000000000000..0aedc5c70b632
--- /dev/null
+++ b/fs/xfs/scrub/orphanage.c
@@ -0,0 +1,499 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021-2024 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_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_inode.h"
+#include "xfs_ialloc.h"
+#include "xfs_quota.h"
+#include "xfs_trans_space.h"
+#include "xfs_dir2.h"
+#include "xfs_icache.h"
+#include "xfs_bmap.h"
+#include "xfs_bmap_btree.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/repair.h"
+#include "scrub/trace.h"
+#include "scrub/orphanage.h"
+#include "scrub/readdir.h"
+
+#include <linux/namei.h>
+
+/*
+ * The Orphanage
+ * =============
+ *
+ * If the directory tree is damaged, children of that directory become
+ * inaccessible via that file path. If a child has no other parents, the file
+ * is said to be orphaned. xfs_repair fixes this situation by creating a
+ * orphanage directory (specifically, /lost+found) and creating a directory
+ * entry pointing to the orphaned file.
+ *
+ * Online repair follows this tactic by creating a root-owned /lost+found
+ * directory if one does not exist. If an orphan is found, it will move that
+ * files into orphanage.
+ */
+
+/* Make the orphanage owned by root. */
+STATIC int
+xrep_chown_orphanage(
+ struct xfs_scrub *sc,
+ struct xfs_inode *dp)
+{
+ struct xfs_trans *tp;
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_dquot *udqp = NULL, *gdqp = NULL, *pdqp = NULL;
+ struct xfs_dquot *oldu = NULL, *oldg = NULL, *oldp = NULL;
+ struct inode *inode = VFS_I(dp);
+ int error;
+
+ error = xfs_qm_vop_dqalloc(dp, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, 0,
+ XFS_QMOPT_QUOTALL, &udqp, &gdqp, &pdqp);
+ if (error)
+ return error;
+
+ error = xfs_trans_alloc_ichange(dp, udqp, gdqp, pdqp, true, &tp);
+ if (error)
+ goto out_dqrele;
+
+ /*
+ * Always clear setuid/setgid/sticky on the orphanage since we don't
+ * normally want that functionality on this directory and xfs_repair
+ * doesn't create it this way either. Leave the other access bits
+ * unchanged.
+ */
+ inode->i_mode &= ~(S_ISUID | S_ISGID | S_ISVTX);
+
+ /*
+ * Change the ownerships and register quota modifications
+ * in the transaction.
+ */
+ if (!uid_eq(inode->i_uid, GLOBAL_ROOT_UID)) {
+ if (XFS_IS_UQUOTA_ON(mp))
+ oldu = xfs_qm_vop_chown(tp, dp, &dp->i_udquot, udqp);
+ inode->i_uid = GLOBAL_ROOT_UID;
+ }
+ if (!gid_eq(inode->i_gid, GLOBAL_ROOT_GID)) {
+ if (XFS_IS_GQUOTA_ON(mp))
+ oldg = xfs_qm_vop_chown(tp, dp, &dp->i_gdquot, gdqp);
+ inode->i_gid = GLOBAL_ROOT_GID;
+ }
+ if (dp->i_projid != 0) {
+ if (XFS_IS_PQUOTA_ON(mp))
+ oldp = xfs_qm_vop_chown(tp, dp, &dp->i_pdquot, pdqp);
+ dp->i_projid = 0;
+ }
+
+ dp->i_diflags &= ~(XFS_DIFLAG_REALTIME | XFS_DIFLAG_RTINHERIT);
+ xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
+
+ XFS_STATS_INC(mp, xs_ig_attrchg);
+
+ if (xfs_has_wsync(mp))
+ xfs_trans_set_sync(tp);
+ error = xfs_trans_commit(tp);
+
+ xfs_qm_dqrele(oldu);
+ xfs_qm_dqrele(oldg);
+ xfs_qm_dqrele(oldp);
+
+out_dqrele:
+ xfs_qm_dqrele(udqp);
+ xfs_qm_dqrele(gdqp);
+ xfs_qm_dqrele(pdqp);
+ return error;
+}
+
+#define ORPHANAGE "lost+found"
+
+/* Create the orphanage directory, and set sc->orphanage to it. */
+int
+xrep_orphanage_create(
+ struct xfs_scrub *sc)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct dentry *root_dentry, *orphanage_dentry;
+ struct inode *root_inode = VFS_I(sc->mp->m_rootip);
+ struct inode *orphanage_inode;
+ int error;
+
+ if (xfs_is_shutdown(mp))
+ return -EIO;
+ if (xfs_is_readonly(mp)) {
+ sc->orphanage = NULL;
+ return 0;
+ }
+
+ ASSERT(sc->tp == NULL);
+ ASSERT(sc->orphanage == NULL);
+
+ /* Find the dentry for the root directory... */
+ root_dentry = d_find_alias(root_inode);
+ if (!root_dentry) {
+ error = -EFSCORRUPTED;
+ goto out;
+ }
+
+ /* ...which is a directory, right? */
+ if (!d_is_dir(root_dentry)) {
+ error = -EFSCORRUPTED;
+ goto out_dput_root;
+ }
+
+ /* Try to find the orphanage directory. */
+ inode_lock_nested(root_inode, I_MUTEX_PARENT);
+ orphanage_dentry = lookup_one_len(ORPHANAGE, root_dentry,
+ strlen(ORPHANAGE));
+ if (IS_ERR(orphanage_dentry)) {
+ error = PTR_ERR(orphanage_dentry);
+ goto out_unlock_root;
+ }
+
+ /*
+ * Nothing found? Call mkdir to create the orphanage. Create the
+ * directory without other-user access because we're live and someone
+ * could have been relying partly on minimal access to a parent
+ * directory to control access to a file we put in here.
+ */
+ if (d_really_is_negative(orphanage_dentry)) {
+ error = vfs_mkdir(&nop_mnt_idmap, root_inode, orphanage_dentry,
+ 0750);
+ if (error)
+ goto out_dput_orphanage;
+ }
+
+ /* Not a directory? Bail out. */
+ if (!d_is_dir(orphanage_dentry)) {
+ error = -ENOTDIR;
+ goto out_dput_orphanage;
+ }
+
+ /*
+ * Grab a reference to the orphanage. This /should/ succeed since
+ * we hold the root directory locked and therefore nobody can delete
+ * the orphanage.
+ */
+ orphanage_inode = igrab(d_inode(orphanage_dentry));
+ if (!orphanage_inode) {
+ error = -ENOENT;
+ goto out_dput_orphanage;
+ }
+
+ /* Make sure the orphanage is owned by root. */
+ error = xrep_chown_orphanage(sc, XFS_I(orphanage_inode));
+ if (error)
+ goto out_dput_orphanage;
+
+ /* Stash the reference for later and bail out. */
+ sc->orphanage = XFS_I(orphanage_inode);
+ sc->orphanage_ilock_flags = 0;
+
+out_dput_orphanage:
+ dput(orphanage_dentry);
+out_unlock_root:
+ inode_unlock(VFS_I(sc->mp->m_rootip));
+out_dput_root:
+ dput(root_dentry);
+out:
+ return error;
+}
+
+void
+xrep_orphanage_ilock(
+ struct xfs_scrub *sc,
+ unsigned int ilock_flags)
+{
+ sc->orphanage_ilock_flags |= ilock_flags;
+ xfs_ilock(sc->orphanage, ilock_flags);
+}
+
+bool
+xrep_orphanage_ilock_nowait(
+ struct xfs_scrub *sc,
+ unsigned int ilock_flags)
+{
+ if (xfs_ilock_nowait(sc->orphanage, ilock_flags)) {
+ sc->orphanage_ilock_flags |= ilock_flags;
+ return true;
+ }
+
+ return false;
+}
+
+void
+xrep_orphanage_iunlock(
+ struct xfs_scrub *sc,
+ unsigned int ilock_flags)
+{
+ xfs_iunlock(sc->orphanage, ilock_flags);
+ sc->orphanage_ilock_flags &= ~ilock_flags;
+}
+
+/* Grab the IOLOCK of the orphanage and sc->ip. */
+int
+xrep_orphanage_iolock_two(
+ struct xfs_scrub *sc)
+{
+ int error = 0;
+
+ while (true) {
+ if (xchk_should_terminate(sc, &error))
+ return error;
+
+ /*
+ * Normal XFS takes the IOLOCK before grabbing a transaction.
+ * Scrub holds a transaction, which means that we can't block
+ * on either IOLOCK.
+ */
+ if (xrep_orphanage_ilock_nowait(sc, XFS_IOLOCK_EXCL)) {
+ if (xchk_ilock_nowait(sc, XFS_IOLOCK_EXCL))
+ break;
+ xrep_orphanage_iunlock(sc, XFS_IOLOCK_EXCL);
+ }
+ delay(1);
+ }
+
+ return 0;
+}
+
+/* Release the orphanage. */
+void
+xrep_orphanage_rele(
+ struct xfs_scrub *sc)
+{
+ if (!sc->orphanage)
+ return;
+
+ if (sc->orphanage_ilock_flags)
+ xfs_iunlock(sc->orphanage, sc->orphanage_ilock_flags);
+
+ xchk_irele(sc, sc->orphanage);
+ sc->orphanage = NULL;
+}
+
+/* Adoption moves a file into /lost+found */
+
+/* Can the orphanage adopt @sc->ip? */
+bool
+xrep_orphanage_can_adopt(
+ struct xfs_scrub *sc)
+{
+ ASSERT(sc->ip != NULL);
+
+ if (!sc->orphanage)
+ return false;
+ if (sc->ip == sc->orphanage)
+ return false;
+ if (xfs_internal_inum(sc->mp, sc->ip->i_ino))
+ return false;
+ return true;
+}
+
+/*
+ * Create a new transaction to send a child to the orphanage.
+ *
+ * Allocate a new transaction with sufficient disk space to handle the
+ * adoption, take ILOCK_EXCL of the orphanage and sc->ip, joins them to the
+ * transaction, and reserve quota to reparent the latter. Caller must hold the
+ * IOLOCK of the orphanage and sc->ip.
+ */
+int
+xrep_adoption_trans_alloc(
+ struct xfs_scrub *sc,
+ struct xrep_adoption *adopt)
+{
+ struct xfs_mount *mp = sc->mp;
+ unsigned int child_blkres = 0;
+ int error;
+
+ ASSERT(sc->tp == NULL);
+ ASSERT(sc->ip != NULL);
+ ASSERT(sc->orphanage != NULL);
+ ASSERT(sc->ilock_flags & XFS_IOLOCK_EXCL);
+ ASSERT(sc->orphanage_ilock_flags & XFS_IOLOCK_EXCL);
+ ASSERT(!(sc->ilock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)));
+ ASSERT(!(sc->orphanage_ilock_flags &
+ (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)));
+
+ /* Compute the worst case space reservation that we need. */
+ adopt->sc = sc;
+ adopt->orphanage_blkres = XFS_LINK_SPACE_RES(mp, MAXNAMELEN);
+ if (S_ISDIR(VFS_I(sc->ip)->i_mode))
+ child_blkres = XFS_RENAME_SPACE_RES(mp, xfs_name_dotdot.len);
+ adopt->child_blkres = child_blkres;
+
+ /*
+ * Allocate a transaction to link the child into the parent, along with
+ * enough disk space to handle expansion of both the orphanage and the
+ * dotdot entry of a child directory.
+ */
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_link,
+ adopt->orphanage_blkres + adopt->child_blkres, 0, 0,
+ &sc->tp);
+ if (error)
+ return error;
+
+ xfs_lock_two_inodes(sc->orphanage, XFS_ILOCK_EXCL,
+ sc->ip, XFS_ILOCK_EXCL);
+ sc->ilock_flags |= XFS_ILOCK_EXCL;
+ sc->orphanage_ilock_flags |= XFS_ILOCK_EXCL;
+
+ xfs_trans_ijoin(sc->tp, sc->orphanage, 0);
+ xfs_trans_ijoin(sc->tp, sc->ip, 0);
+
+ /*
+ * Reserve enough quota in the orphan directory to add the new name.
+ * Normally the orphanage should have user/group/project ids of zero
+ * and hence is not subject to quota enforcement, but we're allowed to
+ * exceed quota to reattach disconnected parts of the directory tree.
+ */
+ error = xfs_trans_reserve_quota_nblks(sc->tp, sc->orphanage,
+ adopt->orphanage_blkres, 0, true);
+ if (error)
+ goto out_cancel;
+
+ /*
+ * Reserve enough quota in the child directory to change dotdot.
+ * Here we're also allowed to exceed file quota to repair inconsistent
+ * metadata.
+ */
+ if (adopt->child_blkres) {
+ error = xfs_trans_reserve_quota_nblks(sc->tp, sc->ip,
+ adopt->child_blkres, 0, true);
+ if (error)
+ goto out_cancel;
+ }
+
+ return 0;
+out_cancel:
+ xchk_trans_cancel(sc);
+ xrep_orphanage_iunlock(sc, XFS_ILOCK_EXCL);
+ xrep_orphanage_iunlock(sc, XFS_IOLOCK_EXCL);
+ return error;
+}
+
+/*
+ * Compute the xfs_name for the directory entry that we're adding to the
+ * orphanage. Caller must hold ILOCKs of sc->ip and the orphanage and must not
+ * reuse namebuf until the adoption completes or is dissolved.
+ */
+int
+xrep_adoption_compute_name(
+ struct xrep_adoption *adopt,
+ unsigned char *namebuf)
+{
+ struct xfs_name *xname = &adopt->xname;
+ struct xfs_scrub *sc = adopt->sc;
+ xfs_ino_t ino;
+ unsigned int incr = 0;
+ int error = 0;
+
+ xname->name = namebuf;
+ xname->len = snprintf(namebuf, MAXNAMELEN, "%llu", sc->ip->i_ino);
+ xname->type = xfs_mode_to_ftype(VFS_I(sc->ip)->i_mode);
+
+ /* Make sure the filename is unique in the lost+found. */
+ error = xchk_dir_lookup(sc, sc->orphanage, xname, &ino);
+ while (error == 0 && incr < 10000) {
+ xname->len = snprintf(namebuf, MAXNAMELEN, "%llu.%u",
+ sc->ip->i_ino, ++incr);
+ error = xchk_dir_lookup(sc, sc->orphanage, xname, &ino);
+ }
+ if (error == 0) {
+ /* We already have 10,000 entries in the orphanage? */
+ return -EFSCORRUPTED;
+ }
+
+ if (error != -ENOENT)
+ return error;
+ return 0;
+}
+
+/*
+ * Move the current file to the orphanage under the computed name.
+ *
+ * Returns with a dirty transaction so that the caller can handle any other
+ * work, such as fixing up unlinked lists or resetting link counts.
+ */
+int
+xrep_adoption_move(
+ struct xrep_adoption *adopt)
+{
+ struct xfs_scrub *sc = adopt->sc;
+ struct xfs_name *xname = &adopt->xname;
+ bool isdir = S_ISDIR(VFS_I(sc->ip)->i_mode);
+ int error;
+
+ trace_xrep_adoption_reparent(sc->orphanage, &adopt->xname,
+ sc->ip->i_ino);
+
+ /* Create the new name in the orphanage. */
+ error = xfs_dir_createname(sc->tp, sc->orphanage, xname, sc->ip->i_ino,
+ adopt->orphanage_blkres);
+ if (error)
+ return error;
+
+ /*
+ * Bump the link count of the orphanage if we just added a
+ * subdirectory, and update its timestamps.
+ */
+ xfs_trans_ichgtime(sc->tp, sc->orphanage,
+ XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
+ if (isdir)
+ xfs_bumplink(sc->tp, sc->orphanage);
+ xfs_trans_log_inode(sc->tp, sc->orphanage, XFS_ILOG_CORE);
+
+ /* Replace the dotdot entry if the child is a subdirectory. */
+ if (isdir) {
+ error = xfs_dir_replace(sc->tp, sc->ip, &xfs_name_dotdot,
+ sc->orphanage->i_ino, adopt->child_blkres);
+ if (error)
+ return error;
+ }
+
+ /*
+ * Notify dirent hooks that we moved the file to /lost+found, and
+ * finish all the deferred work so that we know the adoption is fully
+ * recorded in the log.
+ */
+ xfs_dir_update_hook(sc->orphanage, sc->ip, 1, xname);
+ return 0;
+}
+
+/*
+ * Roll to a clean scrub transaction so that we can release the orphanage,
+ * even if xrep_adoption_move was not called.
+ *
+ * Commits all the work and deferred ops attached to an adoption request and
+ * rolls to a clean scrub transaction. On success, returns 0 with the scrub
+ * context holding a clean transaction with no inodes joined. On failure,
+ * returns negative errno with no scrub transaction. All inode locks are
+ * still held after this function returns.
+ */
+int
+xrep_adoption_trans_roll(
+ struct xrep_adoption *adopt)
+{
+ struct xfs_scrub *sc = adopt->sc;
+ int error;
+
+ trace_xrep_adoption_trans_roll(sc->orphanage, sc->ip,
+ !!(sc->tp->t_flags & XFS_TRANS_DIRTY));
+
+ /* Finish all the deferred ops to commit all repairs. */
+ error = xrep_defer_finish(sc);
+ if (error)
+ return error;
+
+ /* Roll the transaction once more to detach the inodes. */
+ return xfs_trans_roll(&sc->tp);
+}
diff --git a/fs/xfs/scrub/orphanage.h b/fs/xfs/scrub/orphanage.h
new file mode 100644
index 0000000000000..9d40992583b24
--- /dev/null
+++ b/fs/xfs/scrub/orphanage.h
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021-2024 Oracle. All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef __XFS_SCRUB_ORPHANAGE_H__
+#define __XFS_SCRUB_ORPHANAGE_H__
+
+#ifdef CONFIG_XFS_ONLINE_REPAIR
+int xrep_orphanage_create(struct xfs_scrub *sc);
+
+/*
+ * If we're doing a repair, ensure that the orphanage exists and attach it to
+ * the scrub context.
+ */
+static inline int
+xrep_orphanage_try_create(
+ struct xfs_scrub *sc)
+{
+ int error;
+
+ ASSERT(sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR);
+
+ error = xrep_orphanage_create(sc);
+ switch (error) {
+ case 0:
+ case -ENOENT:
+ case -ENOTDIR:
+ case -ENOSPC:
+ /*
+ * If the orphanage can't be found or isn't a directory, we'll
+ * keep going, but we won't be able to attach the file to the
+ * orphanage if we can't find the parent.
+ */
+ return 0;
+ }
+
+ return error;
+}
+
+int xrep_orphanage_iolock_two(struct xfs_scrub *sc);
+
+void xrep_orphanage_ilock(struct xfs_scrub *sc, unsigned int ilock_flags);
+bool xrep_orphanage_ilock_nowait(struct xfs_scrub *sc,
+ unsigned int ilock_flags);
+void xrep_orphanage_iunlock(struct xfs_scrub *sc, unsigned int ilock_flags);
+
+void xrep_orphanage_rele(struct xfs_scrub *sc);
+
+/* Information about a request to add a file to the orphanage. */
+struct xrep_adoption {
+ /* Name structure; caller must provide a buffer separately. */
+ struct xfs_name xname;
+
+ struct xfs_scrub *sc;
+
+ /* Block reservations for orphanage and child (if directory). */
+ unsigned int orphanage_blkres;
+ unsigned int child_blkres;
+};
+
+bool xrep_orphanage_can_adopt(struct xfs_scrub *sc);
+
+int xrep_adoption_trans_alloc(struct xfs_scrub *sc,
+ struct xrep_adoption *adopt);
+int xrep_adoption_compute_name(struct xrep_adoption *adopt,
+ unsigned char *namebuf);
+int xrep_adoption_move(struct xrep_adoption *adopt);
+int xrep_adoption_trans_roll(struct xrep_adoption *adopt);
+#else
+struct xrep_adoption { /* empty */ };
+# define xrep_orphanage_rele(sc) ((void)0)
+#endif /* CONFIG_XFS_ONLINE_REPAIR */
+
+#endif /* __XFS_SCRUB_ORPHANAGE_H__ */
diff --git a/fs/xfs/scrub/parent_repair.c b/fs/xfs/scrub/parent_repair.c
index 430f95171b50b..2eb0dbde9c459 100644
--- a/fs/xfs/scrub/parent_repair.c
+++ b/fs/xfs/scrub/parent_repair.c
@@ -32,6 +32,8 @@
#include "scrub/iscan.h"
#include "scrub/findparent.h"
#include "scrub/readdir.h"
+#include "scrub/tempfile.h"
+#include "scrub/orphanage.h"

/*
* Repairing The Directory Parent Pointer
@@ -57,6 +59,12 @@ struct xrep_parent {
* dotdot entry for this directory.
*/
struct xrep_parent_scan_info pscan;
+
+ /* Orphanage reparenting request. */
+ struct xrep_adoption adoption;
+
+ /* Directory entry name, plus the trailing null. */
+ unsigned char namebuf[MAXNAMELEN];
};

/* Tear down all the incore stuff we created. */
@@ -82,7 +90,7 @@ xrep_setup_parent(
rp->sc = sc;
sc->buf = rp;

- return 0;
+ return xrep_orphanage_try_create(sc);
}

/*
@@ -179,6 +187,91 @@ xrep_parent_reset_dotdot(
return xfs_trans_roll(&sc->tp);
}

+/*
+ * Move the current file to the orphanage.
+ *
+ * Caller must hold IOLOCK_EXCL on @sc->ip, and no other inode locks. Upon
+ * successful return, the scrub transaction will have enough extra reservation
+ * to make the move; it will hold IOLOCK_EXCL and ILOCK_EXCL of @sc->ip and the
+ * orphanage; and both inodes will be ijoined.
+ */
+STATIC int
+xrep_parent_move_to_orphanage(
+ struct xrep_parent *rp)
+{
+ struct xfs_scrub *sc = rp->sc;
+ xfs_ino_t orig_parent, new_parent;
+ int error;
+
+ /*
+ * We are about to drop the ILOCK on sc->ip to lock the orphanage and
+ * prepare for the adoption. Therefore, look up the old dotdot entry
+ * for sc->ip so that we can compare it after we re-lock sc->ip.
+ */
+ error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &orig_parent);
+ if (error)
+ return error;
+
+ /*
+ * Drop the ILOCK on the scrub target and commit the transaction.
+ * Adoption computes its own resource requirements and gathers the
+ * necessary components.
+ */
+ error = xrep_trans_commit(sc);
+ if (error)
+ return error;
+ xchk_iunlock(sc, XFS_ILOCK_EXCL);
+
+ /* If we can take the orphanage's iolock then we're ready to move. */
+ if (!xrep_orphanage_ilock_nowait(sc, XFS_IOLOCK_EXCL)) {
+ xchk_iunlock(sc, sc->ilock_flags);
+ error = xrep_orphanage_iolock_two(sc);
+ if (error)
+ return error;
+ }
+
+ /* Grab transaction and ILOCK the two files. */
+ error = xrep_adoption_trans_alloc(sc, &rp->adoption);
+ if (error)
+ return error;
+
+ error = xrep_adoption_compute_name(&rp->adoption, rp->namebuf);
+ if (error)
+ return error;
+
+ /*
+ * Now that we've reacquired the ILOCK on sc->ip, look up the dotdot
+ * entry again. If the parent changed or the child was unlinked while
+ * the child directory was unlocked, we don't need to move the child to
+ * the orphanage after all.
+ */
+ error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &new_parent);
+ if (error)
+ return error;
+
+ /*
+ * Attach to the orphanage if we still have a linked directory and it
+ * hasn't been moved.
+ */
+ if (orig_parent == new_parent && VFS_I(sc->ip)->i_nlink > 0) {
+ error = xrep_adoption_move(&rp->adoption);
+ if (error)
+ return error;
+ }
+
+ /*
+ * Launder the scrub transaction so we can drop the orphanage ILOCK
+ * and IOLOCK. Return holding the scrub target's ILOCK and IOLOCK.
+ */
+ error = xrep_adoption_trans_roll(&rp->adoption);
+ if (error)
+ return error;
+
+ xrep_orphanage_iunlock(sc, XFS_ILOCK_EXCL);
+ xrep_orphanage_iunlock(sc, XFS_IOLOCK_EXCL);
+ return 0;
+}
+
/*
* Commit the new parent pointer structure (currently only the dotdot entry) to
* the file that we're repairing.
@@ -188,7 +281,8 @@ xrep_parent_rebuild_tree(
struct xrep_parent *rp)
{
if (rp->pscan.parent_ino == NULLFSINO) {
- /* Cannot fix orphaned directories yet. */
+ if (xrep_orphanage_can_adopt(rp->sc))
+ return xrep_parent_move_to_orphanage(rp);
return -EFSCORRUPTED;
}

diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index f9455502b4170..0d35f1f30d9be 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -27,6 +27,7 @@
#include "scrub/stats.h"
#include "scrub/xfile.h"
#include "scrub/tempfile.h"
+#include "scrub/orphanage.h"

/*
* Online Scrub and Repair
@@ -220,6 +221,7 @@ xchk_teardown(
}

xrep_tempfile_rele(sc);
+ xrep_orphanage_rele(sc);
xchk_fsgates_disable(sc);
return error;
}
diff --git a/fs/xfs/scrub/scrub.h b/fs/xfs/scrub/scrub.h
index 48b2fb8271499..09769af6b66a9 100644
--- a/fs/xfs/scrub/scrub.h
+++ b/fs/xfs/scrub/scrub.h
@@ -105,6 +105,10 @@ struct xfs_scrub {
/* Lock flags for @ip. */
uint ilock_flags;

+ /* The orphanage, for stashing files that have lost their parent. */
+ uint orphanage_ilock_flags;
+ struct xfs_inode *orphanage;
+
/* A temporary file on this filesystem, for staging new metadata. */
struct xfs_inode *tempip;
uint temp_ilock_flags;
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 5ccb92214a80d..10b8aa82c2fc8 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -2669,6 +2669,34 @@ DEFINE_EVENT(xrep_dirent_class, name, \
DEFINE_XREP_DIRENT_EVENT(xrep_dir_salvage_entry);
DEFINE_XREP_DIRENT_EVENT(xrep_dir_stash_createname);
DEFINE_XREP_DIRENT_EVENT(xrep_dir_replay_createname);
+DEFINE_XREP_DIRENT_EVENT(xrep_adoption_reparent);
+
+DECLARE_EVENT_CLASS(xrep_adoption_class,
+ TP_PROTO(struct xfs_inode *dp, struct xfs_inode *ip, bool moved),
+ TP_ARGS(dp, ip, moved),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(xfs_ino_t, dir_ino)
+ __field(xfs_ino_t, child_ino)
+ __field(bool, moved)
+ ),
+ TP_fast_assign(
+ __entry->dev = dp->i_mount->m_super->s_dev;
+ __entry->dir_ino = dp->i_ino;
+ __entry->child_ino = ip->i_ino;
+ __entry->moved = moved;
+ ),
+ TP_printk("dev %d:%d dir 0x%llx child 0x%llx moved? %d",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->dir_ino,
+ __entry->child_ino,
+ __entry->moved)
+);
+#define DEFINE_XREP_ADOPTION_EVENT(name) \
+DEFINE_EVENT(xrep_adoption_class, name, \
+ TP_PROTO(struct xfs_inode *dp, struct xfs_inode *ip, bool moved), \
+ TP_ARGS(dp, ip, moved))
+DEFINE_XREP_ADOPTION_EVENT(xrep_adoption_trans_roll);

DECLARE_EVENT_CLASS(xrep_parent_salvage_class,
TP_PROTO(struct xfs_inode *dp, xfs_ino_t ino),
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 0d7dcb128f857..9618c014615f5 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -936,10 +936,10 @@ xfs_droplink(
/*
* Increment the link count on an inode & log the change.
*/
-static void
+void
xfs_bumplink(
- xfs_trans_t *tp,
- xfs_inode_t *ip)
+ struct xfs_trans *tp,
+ struct xfs_inode *ip)
{
xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index f11e91c6e2182..9cee94a0de2c8 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -621,6 +621,7 @@ void xfs_end_io(struct work_struct *work);
int xfs_ilock2_io_mmap(struct xfs_inode *ip1, struct xfs_inode *ip2);
void xfs_iunlock2_io_mmap(struct xfs_inode *ip1, struct xfs_inode *ip2);
void xfs_iunlock2_remapping(struct xfs_inode *ip1, struct xfs_inode *ip2);
+void xfs_bumplink(struct xfs_trans *tp, struct xfs_inode *ip);

static inline bool
xfs_inode_unlinked_incomplete(