[PATCH 1/7] xfs: check dirents have parent pointers

Darrick J. Wong
2024-04-10T01:02:07Z

From: Darrick J. Wong <djwong@kernel.org>

If the fs has parent pointers, we need to check that each child dirent
points to a file that has a parent pointer pointing back at us.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/libxfs/xfs_parent.c | 22 +++++++++
fs/xfs/libxfs/xfs_parent.h | 5 ++
fs/xfs/scrub/dir.c | 112 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 138 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_parent.c b/fs/xfs/libxfs/xfs_parent.c
index db8cfad0b968e..5898dc1ebff02 100644
--- a/fs/xfs/libxfs/xfs_parent.c
+++ b/fs/xfs/libxfs/xfs_parent.c
@@ -294,3 +294,25 @@ xfs_parent_from_xattr(
*parent_gen = be32_to_cpu(rec->p_gen);
return 1;
}
+
+/*
+ * Look up a parent pointer record (@parent_name -> @pptr) of @ip.
+ *
+ * Caller must hold at least ILOCK_SHARED. The scratchpad need not be
+ * initialized.
+ *
+ * Returns 0 if the pointer is found, -ENOATTR if there is no match, or a
+ * negative errno.
+ */
+int
+xfs_parent_lookup(
+ struct xfs_trans *tp,
+ struct xfs_inode *ip,
+ const struct xfs_name *parent_name,
+ struct xfs_parent_rec *pptr,
+ struct xfs_da_args *scratch)
+{
+ memset(scratch, 0, sizeof(struct xfs_da_args));
+ xfs_parent_da_args_init(scratch, tp, pptr, ip, ip->i_ino, parent_name);
+ return xfs_attr_get_ilocked(scratch);
+}
diff --git a/fs/xfs/libxfs/xfs_parent.h b/fs/xfs/libxfs/xfs_parent.h
index 3003ab496f854..b063312a61acb 100644
--- a/fs/xfs/libxfs/xfs_parent.h
+++ b/fs/xfs/libxfs/xfs_parent.h
@@ -96,4 +96,9 @@ int xfs_parent_from_xattr(struct xfs_mount *mp, unsigned int attr_flags,
const void *value, unsigned int valuelen,
xfs_ino_t *parent_ino, uint32_t *parent_gen);

+/* Repair functions */
+int xfs_parent_lookup(struct xfs_trans *tp, struct xfs_inode *ip,
+ const struct xfs_name *name, struct xfs_parent_rec *pptr,
+ struct xfs_da_args *scratch);
+
#endif /* __XFS_PARENT_H__ */
diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
index 3fe6ffcf9c062..e11d73eb89352 100644
--- a/fs/xfs/scrub/dir.c
+++ b/fs/xfs/scrub/dir.c
@@ -16,6 +16,8 @@
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_health.h"
+#include "xfs_attr.h"
+#include "xfs_parent.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/dabtree.h"
@@ -41,6 +43,14 @@ xchk_setup_directory(

/* Directories */

+struct xchk_dir {
+ struct xfs_scrub *sc;
+
+ /* information for parent pointer validation. */
+ struct xfs_parent_rec pptr_rec;
+ struct xfs_da_args pptr_args;
+};
+
/* Scrub a directory entry. */

/* Check that an inode's mode matches a given XFS_DIR3_FT_* type. */
@@ -63,6 +73,90 @@ xchk_dir_check_ftype(
xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
}

+/*
+ * Try to lock a child file for checking parent pointers. Returns the inode
+ * flags for the locks we now hold, or zero if we failed.
+ */
+STATIC unsigned int
+xchk_dir_lock_child(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip)
+{
+ if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
+ return 0;
+
+ if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
+ xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+ return 0;
+ }
+
+ if (!xfs_inode_has_attr_fork(ip) || !xfs_need_iread_extents(&ip->i_af))
+ return XFS_IOLOCK_SHARED | XFS_ILOCK_SHARED;
+
+ xfs_iunlock(ip, XFS_ILOCK_SHARED);
+
+ if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
+ xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+ return 0;
+ }
+
+ return XFS_IOLOCK_SHARED | XFS_ILOCK_EXCL;
+}
+
+/* Check the backwards link (parent pointer) associated with this dirent. */
+STATIC int
+xchk_dir_parent_pointer(
+ struct xchk_dir *sd,
+ const struct xfs_name *name,
+ struct xfs_inode *ip)
+{
+ struct xfs_scrub *sc = sd->sc;
+ int error;
+
+ xfs_inode_to_parent_rec(&sd->pptr_rec, sc->ip);
+ error = xfs_parent_lookup(sc->tp, ip, name, &sd->pptr_rec,
+ &sd->pptr_args);
+ if (error == -ENOATTR)
+ xchk_fblock_xref_set_corrupt(sc, XFS_DATA_FORK, 0);
+
+ return 0;
+}
+
+/* Look for a parent pointer matching this dirent, if the child isn't busy. */
+STATIC int
+xchk_dir_check_pptr_fast(
+ struct xchk_dir *sd,
+ xfs_dir2_dataptr_t dapos,
+ const struct xfs_name *name,
+ struct xfs_inode *ip)
+{
+ struct xfs_scrub *sc = sd->sc;
+ unsigned int lockmode;
+ int error;
+
+ /* dot and dotdot entries do not have parent pointers */
+ if (xfs_dir2_samename(name, &xfs_name_dot) ||
+ xfs_dir2_samename(name, &xfs_name_dotdot))
+ return 0;
+
+ /* No self-referential non-dot or dotdot dirents. */
+ if (ip == sc->ip) {
+ xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ return -ECANCELED;
+ }
+
+ /* Try to lock the inode. */
+ lockmode = xchk_dir_lock_child(sc, ip);
+ if (!lockmode) {
+ xchk_set_incomplete(sc);
+ return -ECANCELED;
+ }
+
+ error = xchk_dir_parent_pointer(sd, name, ip);
+ xfs_iunlock(ip, lockmode);
+ return error;
+}
+
/*
* Scrub a single directory entry.
*
@@ -80,6 +174,7 @@ xchk_dir_actor(
{
struct xfs_mount *mp = dp->i_mount;
struct xfs_inode *ip;
+ struct xchk_dir *sd = priv;
xfs_ino_t lookup_ino;
xfs_dablk_t offset;
int error = 0;
@@ -146,6 +241,14 @@ xchk_dir_actor(
goto out;

xchk_dir_check_ftype(sc, offset, ip, name->type);
+
+ if (xfs_has_parent(mp)) {
+ error = xchk_dir_check_pptr_fast(sd, dapos, name, ip);
+ if (error)
+ goto out_rele;
+ }
+
+out_rele:
xchk_irele(sc, ip);
out:
if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
@@ -767,6 +870,7 @@ int
xchk_directory(
struct xfs_scrub *sc)
{
+ struct xchk_dir *sd;
int error;

if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
@@ -799,8 +903,14 @@ xchk_directory(
if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
return 0;

+ sd = kvzalloc(sizeof(struct xchk_dir), XCHK_GFP_FLAGS);
+ if (!sd)
+ return -ENOMEM;
+ sd->sc = sc;
+
/* Look up every name in this directory by hash. */
- error = xchk_dir_walk(sc, sc->ip, xchk_dir_actor, NULL);
+ error = xchk_dir_walk(sc, sc->ip, xchk_dir_actor, sd);
+ kvfree(sd);
if (error && error != -ECANCELED)
return error;