zfs_rename: support RENAME_* flags

Implement support for Linux's RENAME_* flags (for renameat2). Aside from
being quite useful for userspace (providing race-free ways to exchange
paths and implement mv --no-clobber), they are used by overlayfs and are
thus required in order to use overlayfs-on-ZFS.

In order for us to represent the new renameat2(2) flags in the ZIL, we
create two new transaction types for the two flags which need
transactional-level support (RENAME_EXCHANGE and RENAME_WHITEOUT).
RENAME_NOREPLACE does not need any ZIL support because we know that if
the operation succeeded before creating the ZIL entry, there was no file
to be clobbered and thus it can be treated as a regular TX_RENAME.

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Pavel Snajdr <[email protected]>
Signed-off-by: Aleksa Sarai <[email protected]>
Closes #12209
Closes #14070

1 files changed, 96 insertions, 10 deletions

diff --git a/module/zfs/zfs_replay.c b/module/zfs/zfs_replay.c
index 45c2fa372..5e20ce331 100644
--- a/module/zfs/zfs_replay.c
+++ b/module/zfs/zfs_replay.c
@@ -643,18 +643,21 @@ zfs_replay_link(void *arg1, void *arg2, boolean_t byteswap)
 }
 
 static int
-zfs_replay_rename(void *arg1, void *arg2, boolean_t byteswap)
+do_zfs_replay_rename(zfsvfs_t *zfsvfs, lr_rename_t *lr, char *sname,
+    char *tname, uint64_t rflags, vattr_t *wo_vap)
 {
-	zfsvfs_t *zfsvfs = arg1;
-	lr_rename_t *lr = arg2;
-	char *sname = (char *)(lr + 1);	/* sname and tname follow lr_rename_t */
-	char *tname = sname + strlen(sname) + 1;
 	znode_t *sdzp, *tdzp;
-	int error;
-	int vflg = 0;
+	int error, vflg = 0;
 
-	if (byteswap)
-		byteswap_uint64_array(lr, sizeof (*lr));
+	/* Only Linux currently supports RENAME_* flags. */
+#ifdef __linux__
+	VERIFY0(rflags & ~(RENAME_EXCHANGE | RENAME_WHITEOUT));
+
+	/* wo_vap must be non-NULL iff. we're doing RENAME_WHITEOUT */
+	VERIFY_EQUIV(rflags & RENAME_WHITEOUT, wo_vap != NULL);
+#else
+	VERIFY0(rflags);
+#endif
 
 	if ((error = zfs_zget(zfsvfs, lr->lr_sdoid, &sdzp)) != 0)
 		return (error);
@@ -667,7 +670,8 @@ zfs_replay_rename(void *arg1, void *arg2, boolean_t byteswap)
 	if (lr->lr_common.lrc_txtype & TX_CI)
 		vflg |= FIGNORECASE;
 
-	error = zfs_rename(sdzp, sname, tdzp, tname, kcred, vflg, NULL);
+	error = zfs_rename(sdzp, sname, tdzp, tname, kcred, vflg, rflags,
+	    wo_vap, NULL);
 
 	zrele(tdzp);
 	zrele(sdzp);
@@ -675,6 +679,86 @@ zfs_replay_rename(void *arg1, void *arg2, boolean_t byteswap)
 }
 
 static int
+zfs_replay_rename(void *arg1, void *arg2, boolean_t byteswap)
+{
+	zfsvfs_t *zfsvfs = arg1;
+	lr_rename_t *lr = arg2;
+	char *sname = (char *)(lr + 1);	/* sname and tname follow lr_rename_t */
+	char *tname = sname + strlen(sname) + 1;
+
+	if (byteswap)
+		byteswap_uint64_array(lr, sizeof (*lr));
+
+	return (do_zfs_replay_rename(zfsvfs, lr, sname, tname, 0, NULL));
+}
+
+static int
+zfs_replay_rename_exchange(void *arg1, void *arg2, boolean_t byteswap)
+{
+#ifdef __linux__
+	zfsvfs_t *zfsvfs = arg1;
+	lr_rename_t *lr = arg2;
+	char *sname = (char *)(lr + 1);	/* sname and tname follow lr_rename_t */
+	char *tname = sname + strlen(sname) + 1;
+
+	if (byteswap)
+		byteswap_uint64_array(lr, sizeof (*lr));
+
+	return (do_zfs_replay_rename(zfsvfs, lr, sname, tname, RENAME_EXCHANGE,
+	    NULL));
+#else
+	return (SET_ERROR(ENOTSUP));
+#endif
+}
+
+static int
+zfs_replay_rename_whiteout(void *arg1, void *arg2, boolean_t byteswap)
+{
+#ifdef __linux__
+	zfsvfs_t *zfsvfs = arg1;
+	lr_rename_whiteout_t *lr = arg2;
+	int error;
+	/* sname and tname follow lr_rename_whiteout_t */
+	char *sname = (char *)(lr + 1);
+	char *tname = sname + strlen(sname) + 1;
+	/* For the whiteout file. */
+	xvattr_t xva;
+	uint64_t objid;
+	uint64_t dnodesize;
+
+	if (byteswap)
+		byteswap_uint64_array(lr, sizeof (*lr));
+
+	objid = LR_FOID_GET_OBJ(lr->lr_wfoid);
+	dnodesize = LR_FOID_GET_SLOTS(lr->lr_wfoid) << DNODE_SHIFT;
+
+	xva_init(&xva);
+	zfs_init_vattr(&xva.xva_vattr, ATTR_MODE | ATTR_UID | ATTR_GID,
+	    lr->lr_wmode, lr->lr_wuid, lr->lr_wgid, lr->lr_wrdev, objid);
+
+	/*
+	 * As with TX_CREATE, RENAME_WHITEOUT ends up in zfs_mknode(), which
+	 * assigns the object's creation time, generation number, and dnode
+	 * slot count. The generic zfs_rename() has no concept of these
+	 * attributes, so we smuggle the values inside the vattr's otherwise
+	 * unused va_ctime, va_nblocks, and va_fsid fields.
+	 */
+	ZFS_TIME_DECODE(&xva.xva_vattr.va_ctime, lr->lr_wcrtime);
+	xva.xva_vattr.va_nblocks = lr->lr_wgen;
+	xva.xva_vattr.va_fsid = dnodesize;
+
+	error = dnode_try_claim(zfsvfs->z_os, objid, dnodesize >> DNODE_SHIFT);
+	if (error)
+		return (error);
+
+	return (do_zfs_replay_rename(zfsvfs, &lr->lr_rename, sname, tname,
+	    RENAME_WHITEOUT, &xva.xva_vattr));
+#else
+	return (SET_ERROR(ENOTSUP));
+#endif
+}
+
+static int
 zfs_replay_write(void *arg1, void *arg2, boolean_t byteswap)
 {
 	zfsvfs_t *zfsvfs = arg1;
@@ -1069,4 +1153,6 @@ zil_replay_func_t *const zfs_replay_vector[TX_MAX_TYPE] = {
 	zfs_replay_create_acl,	/* TX_MKDIR_ACL_ATTR */
 	zfs_replay_write2,	/* TX_WRITE2 */
 	zfs_replay_setsaxattr,	/* TX_SETSAXATTR */
+	zfs_replay_rename_exchange,	/* TX_RENAME_EXCHANGE */
+	zfs_replay_rename_whiteout,	/* TX_RENAME_WHITEOUT */
 };