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Make zvol minor functionality more robust

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Close the race window in zvol_open() to prevent removal of
zvol_state in the 'first open' code path. Move the call to
check_disk_change() under zvol_state_lock to make sure the
zvol_media_changed() and zvol_revalidate_disk() called by
check_disk_change() are invoked with positive zv_open_count.

Skip opened zvols when removing minors and set private_data
to NULL for zvols that are not in use whose minors are being
removed, to indicate to zvol_open() that the state is gone.
Skip opened zvols when renaming minors to avoid modifying
zv_name that might be in use, e.g. in zvol_ioctl().

Drop zvol_state_lock before calling add_disk() when creating
minors to avoid deadlocks with zvol_open().

Wrap dmu_objset_find() with spl_fstran_mark()/unmark().

Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes #4344
This commit is contained in:
Boris Protopopov 2016-02-16 14:52:55 -05:00 committed by Brian Behlendorf
parent 19a47cb1c2
commit 5428dc51fb
1 changed files with 77 additions and 16 deletions
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93
module/zfs/zvol.c
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@ -35,6 +35,7 @@
* needs to be run before opening and using a device.
*
* Copyright 2014 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2016 Actifio, Inc. All rights reserved.
*/
#include <sys/dbuf.h>
@ -607,6 +608,8 @@ zvol_write(zvol_state_t *zv, uio_t *uio, boolean_t sync)
rl_t *rl;
int error = 0;
ASSERT(zv && zv->zv_open_count > 0);
rl = zfs_range_lock(&zv->zv_znode, uio->uio_loffset, uio->uio_resid,
RL_WRITER);
@ -675,6 +678,8 @@ zvol_discard(struct bio *bio)
rl_t *rl;
dmu_tx_t *tx;
ASSERT(zv && zv->zv_open_count > 0);
if (end > zv->zv_volsize)
return (SET_ERROR(EIO));
@ -722,6 +727,8 @@ zvol_read(zvol_state_t *zv, uio_t *uio)
rl_t *rl;
int error = 0;
ASSERT(zv && zv->zv_open_count > 0);
rl = zfs_range_lock(&zv->zv_znode, uio->uio_loffset, uio->uio_resid,
RL_READER);
while (uio->uio_resid > 0 && uio->uio_loffset < volsize) {
@ -1020,7 +1027,7 @@ zvol_last_close(zvol_state_t *zv)
static int
zvol_open(struct block_device *bdev, fmode_t flag)
{
zvol_state_t *zv = bdev->bd_disk->private_data;
zvol_state_t *zv;
int error = 0, drop_mutex = 0;
/*
@ -1034,7 +1041,17 @@ zvol_open(struct block_device *bdev, fmode_t flag)
drop_mutex = 1;
}
ASSERT3P(zv, !=, NULL);
/*
* Obtain a copy of private_data under the lock to make sure
* that either the result of zvol_freeg() setting
* bdev->bd_disk->private_data to NULL is observed, or zvol_free()
* is not called on this zv because of the positive zv_open_count.
*/
zv = bdev->bd_disk->private_data;
if (zv == NULL) {
error = -ENXIO;
goto out_mutex;
}
if (zv->zv_open_count == 0) {
error = zvol_first_open(zv);
@ -1049,6 +1066,8 @@ zvol_open(struct block_device *bdev, fmode_t flag)
zv->zv_open_count++;
check_disk_change(bdev);
out_open_count:
if (zv->zv_open_count == 0)
zvol_last_close(zv);
@ -1057,8 +1076,6 @@ out_mutex:
if (drop_mutex)
mutex_exit(&zvol_state_lock);
check_disk_change(bdev);
return (SET_ERROR(error));
}
@ -1072,16 +1089,16 @@ zvol_release(struct gendisk *disk, fmode_t mode)
zvol_state_t *zv = disk->private_data;
int drop_mutex = 0;
ASSERT(zv && zv->zv_open_count > 0);
if (!mutex_owned(&zvol_state_lock)) {
mutex_enter(&zvol_state_lock);
drop_mutex = 1;
}
if (zv->zv_open_count > 0) {
zv->zv_open_count--;
if (zv->zv_open_count == 0)
zvol_last_close(zv);
}
zv->zv_open_count--;
if (zv->zv_open_count == 0)
zvol_last_close(zv);
if (drop_mutex)
mutex_exit(&zvol_state_lock);
@ -1098,8 +1115,7 @@ zvol_ioctl(struct block_device *bdev, fmode_t mode,
zvol_state_t *zv = bdev->bd_disk->private_data;
int error = 0;
if (zv == NULL)
return (SET_ERROR(-ENXIO));
ASSERT(zv && zv->zv_open_count > 0);
switch (cmd) {
case BLKFLSBUF:
@ -1133,6 +1149,8 @@ static int zvol_media_changed(struct gendisk *disk)
{
zvol_state_t *zv = disk->private_data;
ASSERT(zv && zv->zv_open_count > 0);
return (zv->zv_changed);
}
@ -1140,6 +1158,8 @@ static int zvol_revalidate_disk(struct gendisk *disk)
{
zvol_state_t *zv = disk->private_data;
ASSERT(zv && zv->zv_open_count > 0);
zv->zv_changed = 0;
set_capacity(zv->zv_disk, zv->zv_volsize >> 9);
@ -1156,7 +1176,11 @@ static int
zvol_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
zvol_state_t *zv = bdev->bd_disk->private_data;
sector_t sectors = get_capacity(zv->zv_disk);
sector_t sectors;
ASSERT(zv && zv->zv_open_count > 0);
sectors = get_capacity(zv->zv_disk);
if (sectors > 2048) {
geo->heads = 16;
@ -1312,9 +1336,14 @@ out_kmem:
static void
zvol_free(zvol_state_t *zv)
{
ASSERT(MUTEX_HELD(&zvol_state_lock));
ASSERT(zv->zv_open_count == 0);
avl_destroy(&zv->zv_znode.z_range_avl);
mutex_destroy(&zv->zv_znode.z_range_lock);
zv->zv_disk->private_data = NULL;
del_gendisk(zv->zv_disk);
blk_cleanup_queue(zv->zv_queue);
put_disk(zv->zv_disk);
@ -1448,7 +1477,15 @@ out:
if (error == 0) {
zvol_insert(zv);
/*
* Drop the lock to prevent deadlock with sys_open() ->
* zvol_open(), which first takes bd_disk->bd_mutex and then
* takes zvol_state_lock, whereas this code path first takes
* zvol_state_lock, and then takes bd_disk->bd_mutex.
*/
mutex_exit(&zvol_state_lock);
add_disk(zv->zv_disk);
mutex_enter(&zvol_state_lock);
}
return (SET_ERROR(error));
@ -1545,10 +1582,15 @@ int
zvol_create_minors(const char *name)
{
int error = 0;
fstrans_cookie_t cookie;
if (!zvol_inhibit_dev)
error = dmu_objset_find((char *)name, zvol_create_minors_cb,
NULL, DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);
if (zvol_inhibit_dev)
return (0);
cookie = spl_fstrans_mark();
error = dmu_objset_find((char *)name, zvol_create_minors_cb,
NULL, DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);
spl_fstrans_unmark(cookie);
return (SET_ERROR(error));
}
@ -1572,7 +1614,13 @@ zvol_remove_minors(const char *name)
if (name == NULL || strcmp(zv->zv_name, name) == 0 ||
(strncmp(zv->zv_name, name, namelen) == 0 &&
zv->zv_name[namelen] == '/')) {
(zv->zv_name[namelen] == '/' ||
zv->zv_name[namelen] == '@'))) {
/* If in use, leave alone */
if (zv->zv_open_count > 0)
continue;
zvol_remove(zv);
zvol_free(zv);
}
@ -1603,6 +1651,10 @@ zvol_rename_minors(const char *oldname, const char *newname)
for (zv = list_head(&zvol_state_list); zv != NULL; zv = zv_next) {
zv_next = list_next(&zvol_state_list, zv);
/* If in use, leave alone */
if (zv->zv_open_count > 0)
continue;
if (strcmp(zv->zv_name, oldname) == 0) {
__zvol_rename_minor(zv, newname);
} else if (strncmp(zv->zv_name, oldname, oldnamelen) == 0 &&
@ -1643,8 +1695,17 @@ snapdev_snapshot_changed_cb(const char *dsname, void *arg) {
int
zvol_set_snapdev(const char *dsname, uint64_t snapdev) {
fstrans_cookie_t cookie;
if (zvol_inhibit_dev)
/* caller should continue to modify snapdev property */
return (-1);
cookie = spl_fstrans_mark();
(void) dmu_objset_find((char *) dsname, snapdev_snapshot_changed_cb,
&snapdev, DS_FIND_SNAPSHOTS | DS_FIND_CHILDREN);
spl_fstrans_unmark(cookie);
/* caller should continue to modify snapdev property */
return (-1);
}