Re: zfs related panic

On Fri, Aug 15, 2025 at 11:19:55AM -0700, Bakul Shah wrote:
> Is this a known bug or may be something specific on my machine?
> If the latter, any way to "fsck" it? FYI, the zpool is a mirror
> (two files on the host via nvme). built from c992ac621327 commit hash
> (which has other issues but they seem to be separate from this).
> I saw the same panic when I booted from a day old snapshot.
> 
> Note that "ls /.zfs" panics but "ls /.zfs/snapshot" doesn't!
> 
> This is on a -current VM:
> 
> root@:/ # ls .zfs
> VNASSERT failed: oresid == 0 || nresid != oresid || *(a)->a_eofflag == 1 not true at vnode_if.c:1824 (VOP_READDIR_APV)

Try this, untested.

commit a97fc29bf2c03bbfc57b9c188ab3b24450d453bc
Author: Konstantin Belousov <kib@FreeBSD.org>
Date:   Sat Aug 16 01:50:42 2025 +0300

    zfs control dir: properly set eof

diff --git a/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.c b/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.c
index 61d0bb26d1e5..725c02d47edf 100644
--- a/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.c
+++ b/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.c
@@ -1056,17 +1056,22 @@ zfsctl_snapdir_readdir(struct vop_readdir_args *ap)
 	zfs_uio_t uio;
 	int *eofp = ap->a_eofflag;
 	off_t dots_offset;
+	offset_t orig_resid;
 	int error;
 
 	zfs_uio_init(&uio, ap->a_uio);
+	orig_resid = uio.uio->uio_resid;
 
 	ASSERT3S(vp->v_type, ==, VDIR);
 
 	error = sfs_readdir_common(ZFSCTL_INO_ROOT, ZFSCTL_INO_SNAPDIR, ap,
 	    &uio, &dots_offset);
 	if (error != 0) {
-		if (error == ENAMETOOLONG) /* ran out of destination space */
+		if (error == ENAMETOOLONG) { /* ran out of destination space */
 			error = 0;
+			if (orig_resid == uio.uio->uio_resid && eofp != NULL)
+				*eofp = 1;
+		}
 		return (error);
 	}
 
@@ -1084,7 +1089,8 @@ zfsctl_snapdir_readdir(struct vop_readdir_args *ap)
 		dsl_pool_config_exit(dmu_objset_pool(zfsvfs->z_os), FTAG);
 		if (error != 0) {
 			if (error == ENOENT) {
-				if (eofp != NULL)
+				if (orig_resid == uio.uio->uio_resid &&
+				    eofp != NULL)
 					*eofp = 1;
 				error = 0;
 			}
@@ -1099,8 +1105,12 @@ zfsctl_snapdir_readdir(struct vop_readdir_args *ap)
 		entry.d_reclen = sizeof (entry);
 		error = vfs_read_dirent(ap, &entry, zfs_uio_offset(&uio));
 		if (error != 0) {
-			if (error == ENAMETOOLONG)
+			if (error == ENAMETOOLONG) {
 				error = 0;
+				if (orig_resid == uio.uio->uio_resid &&
+				    eofp != NULL)
+					*eofp = 1;
+			}
 			zfs_exit(zfsvfs, FTAG);
 			return (SET_ERROR(error));
 		}