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zvol: remove the OS-side minor before freeing the zvol

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When destroying a zvol, it is not "unpublished" from the system (that
is, /dev/zd* node removed) until zvol_os_free(). Under Linux, at the
time del_gendisk() and put_disk() are called, the device node may still
be have an active hold, from a userspace program or something inside the
kernel (a partition probe). As it is currently, this can lead to calls
to zvol_open() or zvol_release() while the zvol_state_t is partially or
fully freed. zvol_open() has some protection against this by checking
that private_data is NULL, but zvol_release does not.

This implements a better ordering for all of this by adding a new
OS-side method, zvol_os_remove_minor(), which is responsible for fully
decoupling the "private" (OS-side) objects from the zvol_state_t. For
Linux, that means calling put_disk(), nulling private_data, and freeing
zv_zso.

This takes the place of zvol_os_clear_private(), which was a nod in that
direction but did not do enough, and did not do it early enough.

Equivalent changes are made on the FreeBSD side to follow the API
change.

Sponsored-by: Klara, Inc.
Sponsored-by: Railway Corporation
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Fedor Uporov <fuporov.vstack@gmail.com>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #17625
This commit is contained in:
Rob Norris
2025-08-05 13:43:17 +10:00
committed by Brian Behlendorf
parent b2c792778c
commit 96f9d271ea
4 changed files with 99 additions and 96 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/os/linux/zfs/zvol_os.c
+54 -32
View File
@@ -22,7 +22,7 @@
/*
* Copyright (c) 2012, 2020 by Delphix. All rights reserved.
* Copyright (c) 2024, Rob Norris <robn@despairlabs.com>
* Copyright (c) 2024, Klara, Inc.
* Copyright (c) 2024, 2025, Klara, Inc.
*/
#include <sys/dataset_kstats.h>
@@ -971,16 +971,6 @@ zvol_os_update_volsize(zvol_state_t *zv, uint64_t volsize)
return (0);
}
void
zvol_os_clear_private(zvol_state_t *zv)
{
/*
* Cleared while holding zvol_state_lock as a writer
* which will prevent zvol_open() from opening it.
*/
zv->zv_zso->zvo_disk->private_data = NULL;
}
/*
* Provide a simple virtual geometry for legacy compatibility. For devices
* smaller than 1 MiB a small head and sector count is used to allow very
@@ -1417,6 +1407,54 @@ out_kmem:
return (ret);
}
void
zvol_os_remove_minor(zvol_state_t *zv)
{
ASSERT(MUTEX_HELD(&zv->zv_state_lock));
ASSERT0(zv->zv_open_count);
ASSERT0(atomic_read(&zv->zv_suspend_ref));
ASSERT(zv->zv_flags & ZVOL_REMOVING);
/*
* Cleared while holding zvol_state_lock as a writer
* which will prevent zvol_open() from opening it.
*/
struct zvol_state_os *zso = zv->zv_zso;
zv->zv_zso = NULL;
/* Clearing private_data will make new callers return immediately. */
zso->zvo_disk->private_data = NULL;
/*
* Drop the state lock before calling del_gendisk(). There may be
* callers waiting to acquire it, but del_gendisk() will block until
* they exit, which would deadlock.
*/
mutex_exit(&zv->zv_state_lock);
del_gendisk(zso->zvo_disk);
#if defined(HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS) && \
(defined(HAVE_BLK_ALLOC_DISK) || defined(HAVE_BLK_ALLOC_DISK_2ARG))
#if defined(HAVE_BLK_CLEANUP_DISK)
blk_cleanup_disk(zso->zvo_disk);
#else
put_disk(zso->zvo_disk);
#endif
#else
blk_cleanup_queue(zso->zvo_queue);
put_disk(zso->zvo_disk);
#endif
if (zso->use_blk_mq)
blk_mq_free_tag_set(&zso->tag_set);
ida_simple_remove(&zvol_ida, MINOR(zso->zvo_dev) >> ZVOL_MINOR_BITS);
kmem_free(zso, sizeof (struct zvol_state_os));
mutex_enter(&zv->zv_state_lock);
}
/*
* Cleanup then free a zvol_state_t which was created by zvol_alloc().
* At this time, the structure is not opened by anyone, is taken off
@@ -1435,35 +1473,19 @@ zvol_os_free(zvol_state_t *zv)
ASSERT(!RW_LOCK_HELD(&zv->zv_suspend_lock));
ASSERT(!MUTEX_HELD(&zv->zv_state_lock));
ASSERT0(zv->zv_open_count);
ASSERT0P(zv->zv_zso->zvo_disk->private_data);
ASSERT0P(zv->zv_zso);
ASSERT0P(zv->zv_objset);
ASSERT0P(zv->zv_zilog);
ASSERT0P(zv->zv_dn);
rw_destroy(&zv->zv_suspend_lock);
zfs_rangelock_fini(&zv->zv_rangelock);
del_gendisk(zv->zv_zso->zvo_disk);
#if defined(HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS) && \
(defined(HAVE_BLK_ALLOC_DISK) || defined(HAVE_BLK_ALLOC_DISK_2ARG))
#if defined(HAVE_BLK_CLEANUP_DISK)
blk_cleanup_disk(zv->zv_zso->zvo_disk);
#else
put_disk(zv->zv_zso->zvo_disk);
#endif
#else
blk_cleanup_queue(zv->zv_zso->zvo_queue);
put_disk(zv->zv_zso->zvo_disk);
#endif
if (zv->zv_zso->use_blk_mq)
blk_mq_free_tag_set(&zv->zv_zso->tag_set);
ida_simple_remove(&zvol_ida,
MINOR(zv->zv_zso->zvo_dev) >> ZVOL_MINOR_BITS);
cv_destroy(&zv->zv_removing_cv);
mutex_destroy(&zv->zv_state_lock);
dataset_kstats_destroy(&zv->zv_kstat);
kmem_free(zv->zv_zso, sizeof (struct zvol_state_os));
kmem_free(zv, sizeof (zvol_state_t));
}