From 56e8ab4a3eff11cae98cbdde6388b8555a97c381 Mon Sep 17 00:00:00 2001
From: Rob Norris <robn@despairlabs.com>
Date: Thu, 4 Sep 2025 04:13:09 +1000
Subject: [PATCH] zvol: reject suspend attempts when zvol is shutting down

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #17690
---
 include/sys/zvol.h     |  2 +-
 module/zfs/zfs_ioctl.c |  4 ++--
 module/zfs/zvol.c      | 23 +++++++++++++++++++----
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/include/sys/zvol.h b/include/sys/zvol.h
index cdc9dba2a..5791246e9 100644
--- a/include/sys/zvol.h
+++ b/include/sys/zvol.h
@@ -53,7 +53,7 @@ extern int zvol_set_volsize(const char *, uint64_t);
 extern int zvol_set_volthreading(const char *, boolean_t);
 extern int zvol_set_common(const char *, zfs_prop_t, zprop_source_t, uint64_t);
 extern int zvol_set_ro(const char *, boolean_t);
-extern zvol_state_handle_t *zvol_suspend(const char *);
+extern int zvol_suspend(const char *, zvol_state_handle_t **);
 extern int zvol_resume(zvol_state_handle_t *);
 extern void *zvol_tag(zvol_state_handle_t *);
 
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 121b966b9..76c9d4ccd 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -4726,7 +4726,7 @@ zfs_ioc_rollback(const char *fsname, nvlist_t *innvl, nvlist_t *outnvl)
 			error = error ? error : resume_err;
 		}
 		zfs_vfs_rele(zfsvfs);
-	} else if ((zv = zvol_suspend(fsname)) != NULL) {
+	} else if (zvol_suspend(fsname, &zv) == 0) {
 		error = dsl_dataset_rollback(fsname, target, zvol_tag(zv),
 		    outnvl);
 		zvol_resume(zv);
@@ -5448,7 +5448,7 @@ zfs_ioc_recv_impl(char *tofs, char *tosnap, const char *origin,
 			}
 			error = error ? error : end_err;
 			zfs_vfs_rele(zfsvfs);
-		} else if ((zv = zvol_suspend(tofs)) != NULL) {
+		} else if (zvol_suspend(tofs, &zv) == 0) {
 			error = dmu_recv_end(&drc, zvol_tag(zv));
 			zvol_resume(zv);
 		} else {
diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 2fd3e1c37..faced0db7 100644
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -1145,20 +1145,34 @@ zvol_tag(zvol_state_t *zv)
 /*
  * Suspend the zvol for recv and rollback.
  */
-zvol_state_t *
-zvol_suspend(const char *name)
+int
+zvol_suspend(const char *name, zvol_state_t **zvp)
 {
 	zvol_state_t *zv;
 
 	zv = zvol_find_by_name(name, RW_WRITER);
 
 	if (zv == NULL)
-		return (NULL);
+		return (SET_ERROR(ENOENT));
 
 	/* block all I/O, release in zvol_resume. */
 	ASSERT(MUTEX_HELD(&zv->zv_state_lock));
 	ASSERT(RW_WRITE_HELD(&zv->zv_suspend_lock));
 
+	/*
+	 * If it's being removed, unlock and return error. It doesn't make any
+	 * sense to try to suspend a zvol being removed, but being here also
+	 * means that zvol_remove_minors_impl() is about to call zvol_remove()
+	 * and then destroy the zvol_state_t, so returning a pointer to it for
+	 * the caller to mess with would be a disaster anyway.
+	 */
+	if (zv->zv_flags & ZVOL_REMOVING) {
+		mutex_exit(&zv->zv_state_lock);
+		rw_exit(&zv->zv_suspend_lock);
+		/* NB: Returning EIO here to match zfsvfs_teardown() */
+		return (SET_ERROR(EIO));
+	}
+
 	atomic_inc(&zv->zv_suspend_ref);
 
 	if (zv->zv_open_count > 0)
@@ -1171,7 +1185,8 @@ zvol_suspend(const char *name)
 	mutex_exit(&zv->zv_state_lock);
 
 	/* zv_suspend_lock is released in zvol_resume() */
-	return (zv);
+	*zvp = zv;
+	return (0);
 }
 
 int