[PATCH 3/3] xfs: ensure dentry consistency when the orphanage adopts a file

Darrick J. Wong
2024-03-27T02:05:38Z

When the orphanage adopts a file, that file becomes a child of the
orphanage. The dentry cache may have entries for the orphanage
directory and the name we've chosen, so (1) make sure we abort if the
dcache has a positive entry because something's not right; and (2)
invalidate and purge negative dentries if the adoption goes through.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/scrub/orphanage.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/scrub/trace.h | 42 ++++++++++++++++++++++
2 files changed, 130 insertions(+)

diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
index 0aedc5c70b632..e1024a7bc9e96 100644
--- a/fs/xfs/scrub/orphanage.c
+++ b/fs/xfs/scrub/orphanage.c
@@ -418,6 +418,87 @@ xrep_adoption_compute_name(
return 0;
}

+/*
+ * Make sure the dcache does not have a positive dentry for the name we've
+ * chosen. The caller should have checked with the ondisk directory, so any
+ * discrepancy is a sign that something is seriously wrong.
+ */
+static int
+xrep_adoption_check_dcache(
+ struct xrep_adoption *adopt)
+{
+ struct qstr qname = QSTR_INIT(adopt->xname.name,
+ adopt->xname.len);
+ struct dentry *d_orphanage, *d_child;
+ int error = 0;
+
+ d_orphanage = d_find_alias(VFS_I(adopt->sc->orphanage));
+ if (!d_orphanage)
+ return 0;
+
+ d_child = d_hash_and_lookup(d_orphanage, &qname);
+ if (d_child) {
+ trace_xrep_adoption_check_child(adopt->sc->mp, d_child);
+
+ if (d_is_positive(d_child)) {
+ ASSERT(d_is_negative(d_child));
+ error = -EFSCORRUPTED;
+ }
+
+ dput(d_child);
+ }
+
+ dput(d_orphanage);
+ if (error)
+ return error;
+
+ /*
+ * Do we need to update d_parent of the dentry for the file being
+ * repaired? In theory there shouldn't be one since the file had
+ * nonzero nlink but wasn't connected to any parent dir.
+ */
+ d_child = d_find_alias(VFS_I(adopt->sc->ip));
+ if (d_child) {
+ trace_xrep_adoption_check_alias(adopt->sc->mp, d_child);
+ ASSERT(d_child->d_parent == NULL);
+
+ dput(d_child);
+ return -EFSCORRUPTED;
+ }
+
+ return 0;
+}
+
+/*
+ * Remove all negative dentries from the dcache. There should not be any
+ * positive entries, since we've maintained our lock on the orphanage
+ * directory.
+ */
+static void
+xrep_adoption_zap_dcache(
+ struct xrep_adoption *adopt)
+{
+ struct qstr qname = QSTR_INIT(adopt->xname.name,
+ adopt->xname.len);
+ struct dentry *d_orphanage, *d_child;
+
+ d_orphanage = d_find_alias(VFS_I(adopt->sc->orphanage));
+ if (!d_orphanage)
+ return;
+
+ d_child = d_hash_and_lookup(d_orphanage, &qname);
+ while (d_child != NULL) {
+ trace_xrep_adoption_invalidate_child(adopt->sc->mp, d_child);
+
+ ASSERT(d_is_negative(d_child));
+ d_invalidate(d_child);
+ dput(d_child);
+ d_child = d_lookup(d_orphanage, &qname);
+ }
+
+ dput(d_orphanage);
+}
+
/*
* Move the current file to the orphanage under the computed name.
*
@@ -436,6 +517,10 @@ xrep_adoption_move(
trace_xrep_adoption_reparent(sc->orphanage, &adopt->xname,
sc->ip->i_ino);

+ error = xrep_adoption_check_dcache(adopt);
+ if (error)
+ return error;
+
/* Create the new name in the orphanage. */
error = xfs_dir_createname(sc->tp, sc->orphanage, xname, sc->ip->i_ino,
adopt->orphanage_blkres);
@@ -466,6 +551,9 @@ xrep_adoption_move(
* recorded in the log.
*/
xfs_dir_update_hook(sc->orphanage, sc->ip, 1, xname);
+
+ /* Remove negative dentries from the lost+found's dcache */
+ xrep_adoption_zap_dcache(adopt);
return 0;
}

diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 618f98cddc3df..7915648012c66 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -2663,6 +2663,48 @@ TRACE_EVENT(xrep_nlinks_set_record,
__entry->children)
);

+DECLARE_EVENT_CLASS(xrep_dentry_class,
+ TP_PROTO(struct xfs_mount *mp, const struct dentry *dentry),
+ TP_ARGS(mp, dentry),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(unsigned int, flags)
+ __field(unsigned long, ino)
+ __field(bool, positive)
+ __field(unsigned long, parent_ino)
+ __field(unsigned int, namelen)
+ __dynamic_array(char, name, dentry->d_name.len)
+ ),
+ TP_fast_assign(
+ __entry->dev = mp->m_super->s_dev;
+ __entry->flags = dentry->d_flags;
+ __entry->positive = d_is_positive(dentry);
+ if (dentry->d_parent && d_inode(dentry->d_parent))
+ __entry->parent_ino = d_inode(dentry->d_parent)->i_ino;
+ else
+ __entry->parent_ino = -1UL;
+ __entry->ino = d_inode(dentry) ? d_inode(dentry)->i_ino : 0;
+ __entry->namelen = dentry->d_name.len;
+ memcpy(__get_str(name), dentry->d_name.name, dentry->d_name.len);
+ ),
+ TP_printk("dev %d:%d flags 0x%x positive? %d parent_ino 0x%lx ino 0x%lx name '%.*s'",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->flags,
+ __entry->positive,
+ __entry->parent_ino,
+ __entry->ino,
+ __entry->namelen,
+ __get_str(name))
+);
+#define DEFINE_REPAIR_DENTRY_EVENT(name) \
+DEFINE_EVENT(xrep_dentry_class, name, \
+ TP_PROTO(struct xfs_mount *mp, const struct dentry *dentry), \
+ TP_ARGS(mp, dentry))
+DEFINE_REPAIR_DENTRY_EVENT(xrep_adoption_check_child);
+DEFINE_REPAIR_DENTRY_EVENT(xrep_adoption_check_alias);
+DEFINE_REPAIR_DENTRY_EVENT(xrep_adoption_check_dentry);
+DEFINE_REPAIR_DENTRY_EVENT(xrep_adoption_invalidate_child);
+
#endif /* IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR) */

#endif /* _TRACE_XFS_SCRUB_TRACE_H */