From: Sergei Shtepa <[email protected]>
The block device filtering mechanism is an API that allows to attach
block device filters. Block device filters allow perform additional
processing for I/O units.
The idea of handling I/O units on block devices is not new. Back in the
2.6 kernel, there was an undocumented possibility of handling I/O units
by substituting the make_request_fn() function, which belonged to the
request_queue structure. But none of the in-tree kernel modules used
this feature, and it was eliminated in the 5.10 kernel.
The block device filtering mechanism returns the ability to handle I/O
units. It is possible to safely attach filter to a block device "on the
fly" without changing the structure of block devices stack.
Co-developed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Tested-by: Donald Buczek <[email protected]>
Tested-by: Fabio Fantoni <[email protected]>
Signed-off-by: Sergei Shtepa <[email protected]>
---
MAINTAINERS | 3 +
block/Makefile | 3 +-
block/bdev.c | 2 +
block/blk-core.c | 35 ++++-
block/blk-filter.c | 238 ++++++++++++++++++++++++++++++++
block/blk.h | 11 ++
block/genhd.c | 10 ++
block/ioctl.c | 7 +
block/partitions/core.c | 9 ++
include/linux/blk-filter.h | 51 +++++++
include/linux/blk_types.h | 1 +
include/linux/blkdev.h | 1 +
include/linux/sched.h | 1 +
include/uapi/linux/blk-filter.h | 35 +++++
include/uapi/linux/fs.h | 3 +
15 files changed, 408 insertions(+), 2 deletions(-)
create mode 100644 block/blk-filter.c
create mode 100644 include/linux/blk-filter.h
create mode 100644 include/uapi/linux/blk-filter.h
diff --git a/MAINTAINERS b/MAINTAINERS
index c20cbec81b58..ef90cd0fec9c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3589,6 +3589,9 @@ M: Sergei Shtepa <[email protected]>
L: [email protected]
S: Supported
F: Documentation/block/blkfilter.rst
+F: block/blk-filter.c
+F: include/linux/blk-filter.h
+F: include/uapi/linux/blk-filter.h
BLOCK LAYER
M: Jens Axboe <[email protected]>
diff --git a/block/Makefile b/block/Makefile
index 46ada9dc8bbf..041c54eb0240 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -9,7 +9,8 @@ obj-y := bdev.o fops.o bio.o elevator.o blk-core.o blk-sysfs.o \
blk-lib.o blk-mq.o blk-mq-tag.o blk-stat.o \
blk-mq-sysfs.o blk-mq-cpumap.o blk-mq-sched.o ioctl.o \
genhd.o ioprio.o badblocks.o partitions/ blk-rq-qos.o \
- disk-events.o blk-ia-ranges.o early-lookup.o
+ disk-events.o blk-ia-ranges.o early-lookup.o \
+ blk-filter.o
obj-$(CONFIG_BOUNCE) += bounce.o
obj-$(CONFIG_BLK_DEV_BSG_COMMON) += bsg.o
diff --git a/block/bdev.c b/block/bdev.c
index e4cfb7adb645..6039d99b3a75 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -412,6 +412,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
return NULL;
}
bdev->bd_disk = disk;
+ bdev->bd_filter = NULL;
return bdev;
}
@@ -1018,6 +1019,7 @@ void bdev_mark_dead(struct block_device *bdev, bool surprise)
}
invalidate_bdev(bdev);
+ blkfilter_detach(bdev);
}
/*
* New drivers should not use this directly. There are some drivers however
diff --git a/block/blk-core.c b/block/blk-core.c
index fdf25b8d6e78..1de74240892a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -18,6 +18,7 @@
#include <linux/blkdev.h>
#include <linux/blk-pm.h>
#include <linux/blk-integrity.h>
+#include <linux/blk-filter.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
@@ -592,12 +593,34 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
static void __submit_bio(struct bio *bio)
{
+ struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+ bool skip_bio = false;
+
+ if (unlikely(bio_queue_enter(bio)))
+ return;
+
+ if (bio->bi_bdev->bd_filter &&
+ bio->bi_bdev->bd_filter != current->blk_filter) {
+ struct blkfilter *prev = current->blk_filter;
+
+ current->blk_filter = bio->bi_bdev->bd_filter;
+ skip_bio = bio->bi_bdev->bd_filter->ops->submit_bio(bio);
+ current->blk_filter = prev;
+ }
+
+ blk_queue_exit(q);
+ if (skip_bio)
+ return;
+
if (unlikely(!blk_crypto_bio_prep(&bio)))
return;
if (!bio->bi_bdev->bd_has_submit_bio) {
blk_mq_submit_bio(bio);
- } else if (likely(bio_queue_enter(bio) == 0)) {
+ return;
+ }
+
+ if (likely(bio_queue_enter(bio) == 0)) {
struct gendisk *disk = bio->bi_bdev->bd_disk;
disk->fops->submit_bio(bio);
@@ -681,6 +704,15 @@ static void __submit_bio_noacct_mq(struct bio *bio)
current->bio_list = NULL;
}
+/**
+ * submit_bio_noacct_nocheck - re-submit a bio to the block device layer for I/O
+ * from block device filter.
+ * @bio: The bio describing the location in memory and on the device.
+ *
+ * This is a version of submit_bio() that shall only be used for I/O that is
+ * resubmitted to lower level by block device filters. All file systems and
+ * other upper level users of the block layer should use submit_bio() instead.
+ */
void submit_bio_noacct_nocheck(struct bio *bio)
{
blk_cgroup_bio_start(bio);
@@ -708,6 +740,7 @@ void submit_bio_noacct_nocheck(struct bio *bio)
else
__submit_bio_noacct(bio);
}
+EXPORT_SYMBOL_GPL(submit_bio_noacct_nocheck);
/**
* submit_bio_noacct - re-submit a bio to the block device layer for I/O
diff --git a/block/blk-filter.c b/block/blk-filter.c
new file mode 100644
index 000000000000..8e2550bed0c5
--- /dev/null
+++ b/block/blk-filter.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (C) 2023 Veeam Software Group GmbH */
+#include <linux/blk-filter.h>
+#include <linux/blk-mq.h>
+#include <linux/module.h>
+
+#include "blk.h"
+
+static LIST_HEAD(blkfilters);
+static DEFINE_SPINLOCK(blkfilters_lock);
+
+static inline struct blkfilter_operations *__blkfilter_find(const char *name)
+{
+ struct blkfilter_operations *ops;
+
+ list_for_each_entry(ops, &blkfilters, link)
+ if (strncmp(ops->name, name, BLKFILTER_NAME_LENGTH) == 0)
+ return ops;
+
+ return NULL;
+}
+
+static inline struct blkfilter_operations *blkfilter_find_get(const char *name)
+{
+ struct blkfilter_operations *ops;
+
+ spin_lock(&blkfilters_lock);
+ ops = __blkfilter_find(name);
+ if (ops && !try_module_get(ops->owner))
+ ops = NULL;
+ spin_unlock(&blkfilters_lock);
+
+ return ops;
+}
+
+static inline void blkfilter_put(const struct blkfilter_operations *ops)
+{
+ module_put(ops->owner);
+}
+
+int blkfilter_ioctl_attach(struct block_device *bdev,
+ struct blkfilter_name __user *argp)
+{
+ struct blkfilter_name name;
+ struct blkfilter_operations *ops;
+ struct blkfilter *flt;
+ int ret;
+
+ if (copy_from_user(&name, argp, sizeof(name)))
+ return -EFAULT;
+
+ ops = blkfilter_find_get(name.name);
+ if (!ops)
+ return -ENOENT;
+
+ mutex_lock(&bdev->bd_disk->open_mutex);
+ if (!disk_live(bdev->bd_disk)) {
+ ret = -ENODEV;
+ goto out_mutex_unlock;
+ }
+ ret = freeze_bdev(bdev);
+ if (ret)
+ goto out_mutex_unlock;
+ blk_mq_freeze_queue(bdev->bd_queue);
+
+ if (bdev->bd_filter) {
+ if (bdev->bd_filter->ops == ops)
+ ret = -EALREADY;
+ else
+ ret = -EBUSY;
+ goto out_unfreeze;
+ }
+
+ flt = ops->attach(bdev);
+ if (IS_ERR(flt)) {
+ ret = PTR_ERR(flt);
+ goto out_unfreeze;
+ }
+
+ flt->ops = ops;
+ bdev->bd_filter = flt;
+
+out_unfreeze:
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+ thaw_bdev(bdev);
+out_mutex_unlock:
+ mutex_unlock(&bdev->bd_disk->open_mutex);
+ if (ret)
+ blkfilter_put(ops);
+ return ret;
+}
+
+static void __blkfilter_detach(struct block_device *bdev)
+{
+ struct blkfilter *flt = bdev->bd_filter;
+ const struct blkfilter_operations *ops = flt->ops;
+
+ bdev->bd_filter = NULL;
+ ops->detach(flt);
+ blkfilter_put(ops);
+}
+
+void blkfilter_detach(struct block_device *bdev)
+{
+ if (bdev->bd_filter) {
+ blk_mq_freeze_queue(bdev->bd_queue);
+ __blkfilter_detach(bdev);
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+ }
+}
+
+int blkfilter_ioctl_detach(struct block_device *bdev,
+ struct blkfilter_name __user *argp)
+{
+ struct blkfilter_name name;
+ int ret = 0;
+
+ if (copy_from_user(&name, argp, sizeof(name)))
+ return -EFAULT;
+
+ mutex_lock(&bdev->bd_disk->open_mutex);
+ if (!disk_live(bdev->bd_disk)) {
+ ret = -ENODEV;
+ goto out_mutex_unlock;
+ }
+ blk_mq_freeze_queue(bdev->bd_queue);
+ if (!bdev->bd_filter) {
+ ret = -ENOENT;
+ goto out_unfreeze;
+ }
+ if (strncmp(bdev->bd_filter->ops->name, name.name,
+ BLKFILTER_NAME_LENGTH)) {
+ ret = -EINVAL;
+ goto out_unfreeze;
+ }
+
+ __blkfilter_detach(bdev);
+out_unfreeze:
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+out_mutex_unlock:
+ mutex_unlock(&bdev->bd_disk->open_mutex);
+ return ret;
+}
+
+int blkfilter_ioctl_ctl(struct block_device *bdev,
+ struct blkfilter_ctl __user *argp)
+{
+ struct blkfilter_ctl ctl;
+ struct blkfilter *flt;
+ int ret;
+
+ if (copy_from_user(&ctl, argp, sizeof(ctl)))
+ return -EFAULT;
+
+ mutex_lock(&bdev->bd_disk->open_mutex);
+ if (!disk_live(bdev->bd_disk)) {
+ ret = -ENODEV;
+ goto out_mutex_unlock;
+ }
+ ret = blk_queue_enter(bdev_get_queue(bdev), 0);
+ if (ret)
+ goto out_mutex_unlock;
+
+ flt = bdev->bd_filter;
+ if (!flt || strncmp(flt->ops->name, ctl.name, BLKFILTER_NAME_LENGTH)) {
+ ret = -ENOENT;
+ goto out_queue_exit;
+ }
+
+ if (!flt->ops->ctl) {
+ ret = -ENOTTY;
+ goto out_queue_exit;
+ }
+
+ ret = flt->ops->ctl(flt, ctl.cmd, u64_to_user_ptr(ctl.opt),
+ &ctl.optlen);
+out_queue_exit:
+ blk_queue_exit(bdev_get_queue(bdev));
+out_mutex_unlock:
+ mutex_unlock(&bdev->bd_disk->open_mutex);
+ return ret;
+}
+
+ssize_t blkfilter_show(struct block_device *bdev, char *buf)
+{
+ ssize_t ret = 0;
+
+ blk_mq_freeze_queue(bdev->bd_queue);
+ if (bdev->bd_filter)
+ ret = sprintf(buf, "%s\n", bdev->bd_filter->ops->name);
+ else
+ ret = sprintf(buf, "\n");
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+
+ return ret;
+}
+
+/**
+ * blkfilter_register() - Register block device filter operations
+ * @ops: The operations to register.
+ *
+ * Return:
+ * 0 if succeeded,
+ * -EBUSY if a block device filter with the same name is already
+ * registered.
+ */
+int blkfilter_register(struct blkfilter_operations *ops)
+{
+ struct blkfilter_operations *found;
+ int ret = 0;
+
+ spin_lock(&blkfilters_lock);
+ found = __blkfilter_find(ops->name);
+ if (found)
+ ret = -EBUSY;
+ else
+ list_add_tail(&ops->link, &blkfilters);
+ spin_unlock(&blkfilters_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blkfilter_register);
+
+/**
+ * blkfilter_unregister() - Unregister block device filter operations
+ * @ops: The operations to unregister.
+ *
+ * Important: before unloading, it is necessary to detach the filter from all
+ * block devices.
+ *
+ */
+void blkfilter_unregister(struct blkfilter_operations *ops)
+{
+ spin_lock(&blkfilters_lock);
+ list_del(&ops->link);
+ spin_unlock(&blkfilters_lock);
+}
+EXPORT_SYMBOL_GPL(blkfilter_unregister);
diff --git a/block/blk.h b/block/blk.h
index 08a358bc0919..1f104f4865c3 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -7,6 +7,8 @@
#include <xen/xen.h>
#include "blk-crypto-internal.h"
+struct blkfilter_ctl;
+struct blkfilter_name;
struct elevator_type;
/* Max future timer expiry for timeouts */
@@ -474,6 +476,15 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg);
extern const struct address_space_operations def_blk_aops;
+int blkfilter_ioctl_attach(struct block_device *bdev,
+ struct blkfilter_name __user *argp);
+int blkfilter_ioctl_detach(struct block_device *bdev,
+ struct blkfilter_name __user *argp);
+int blkfilter_ioctl_ctl(struct block_device *bdev,
+ struct blkfilter_ctl __user *argp);
+void blkfilter_detach(struct block_device *bdev);
+ssize_t blkfilter_show(struct block_device *bdev, char *buf);
+
int disk_register_independent_access_ranges(struct gendisk *disk);
void disk_unregister_independent_access_ranges(struct gendisk *disk);
diff --git a/block/genhd.c b/block/genhd.c
index c9d06f72c587..ba744e3fd581 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -26,6 +26,7 @@
#include <linux/badblocks.h>
#include <linux/part_stat.h>
#include <linux/blktrace_api.h>
+#include <linux/blk-filter.h>
#include "blk-throttle.h"
#include "blk.h"
@@ -654,6 +655,7 @@ void del_gendisk(struct gendisk *disk)
mutex_lock(&disk->open_mutex);
xa_for_each(&disk->part_tbl, idx, part)
remove_inode_hash(part->bd_inode);
+ blkfilter_detach(disk->part0);
mutex_unlock(&disk->open_mutex);
/*
@@ -1044,6 +1046,12 @@ static ssize_t diskseq_show(struct device *dev,
return sprintf(buf, "%llu\n", disk->diskseq);
}
+static ssize_t disk_filter_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return blkfilter_show(dev_to_bdev(dev), buf);
+}
+
static DEVICE_ATTR(range, 0444, disk_range_show, NULL);
static DEVICE_ATTR(ext_range, 0444, disk_ext_range_show, NULL);
static DEVICE_ATTR(removable, 0444, disk_removable_show, NULL);
@@ -1057,6 +1065,7 @@ static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
static DEVICE_ATTR(badblocks, 0644, disk_badblocks_show, disk_badblocks_store);
static DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
+static DEVICE_ATTR(filter, 0444, disk_filter_show, NULL);
#ifdef CONFIG_FAIL_MAKE_REQUEST
ssize_t part_fail_show(struct device *dev,
@@ -1103,6 +1112,7 @@ static struct attribute *disk_attrs[] = {
&dev_attr_events_async.attr,
&dev_attr_events_poll_msecs.attr,
&dev_attr_diskseq.attr,
+ &dev_attr_filter.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
&dev_attr_fail.attr,
#endif
diff --git a/block/ioctl.c b/block/ioctl.c
index 4160f4e6bd5b..1b11303e213b 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -2,6 +2,7 @@
#include <linux/capability.h>
#include <linux/compat.h>
#include <linux/blkdev.h>
+#include <linux/blk-filter.h>
#include <linux/export.h>
#include <linux/gfp.h>
#include <linux/blkpg.h>
@@ -572,6 +573,12 @@ static int blkdev_common_ioctl(struct block_device *bdev, blk_mode_t mode,
return blkdev_pr_preempt(bdev, mode, argp, true);
case IOC_PR_CLEAR:
return blkdev_pr_clear(bdev, mode, argp);
+ case BLKFILTER_ATTACH:
+ return blkfilter_ioctl_attach(bdev, argp);
+ case BLKFILTER_DETACH:
+ return blkfilter_ioctl_detach(bdev, argp);
+ case BLKFILTER_CTL:
+ return blkfilter_ioctl_ctl(bdev, argp);
default:
return -ENOIOCTLCMD;
}
diff --git a/block/partitions/core.c b/block/partitions/core.c
index f47ffcfdfcec..19c69dc23d2c 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -10,6 +10,7 @@
#include <linux/ctype.h>
#include <linux/vmalloc.h>
#include <linux/raid/detect.h>
+#include <linux/blk-filter.h>
#include "check.h"
static int (*const check_part[])(struct parsed_partitions *) = {
@@ -200,6 +201,12 @@ static ssize_t part_discard_alignment_show(struct device *dev,
return sprintf(buf, "%u\n", bdev_discard_alignment(dev_to_bdev(dev)));
}
+static ssize_t part_filter_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return blkfilter_show(dev_to_bdev(dev), buf);
+}
+
static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
static DEVICE_ATTR(start, 0444, part_start_show, NULL);
static DEVICE_ATTR(size, 0444, part_size_show, NULL);
@@ -208,6 +215,7 @@ static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
+static DEVICE_ATTR(filter, 0444, part_filter_show, NULL);
#ifdef CONFIG_FAIL_MAKE_REQUEST
static struct device_attribute dev_attr_fail =
__ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
@@ -222,6 +230,7 @@ static struct attribute *part_attrs[] = {
&dev_attr_discard_alignment.attr,
&dev_attr_stat.attr,
&dev_attr_inflight.attr,
+ &dev_attr_filter.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
&dev_attr_fail.attr,
#endif
diff --git a/include/linux/blk-filter.h b/include/linux/blk-filter.h
new file mode 100644
index 000000000000..0afdb40f3bab
--- /dev/null
+++ b/include/linux/blk-filter.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2023 Veeam Software Group GmbH */
+#ifndef _LINUX_BLK_FILTER_H
+#define _LINUX_BLK_FILTER_H
+
+#include <uapi/linux/blk-filter.h>
+
+struct bio;
+struct block_device;
+struct blkfilter_operations;
+
+/**
+ * struct blkfilter - Block device filter.
+ *
+ * @ops: Block device filter operations.
+ *
+ * For each filtered block device, the filter creates a data structure
+ * associated with this device. The data in this structure is specific to the
+ * filter, but it must contain a pointer to the block device filter account.
+ */
+struct blkfilter {
+ const struct blkfilter_operations *ops;
+};
+
+/**
+ * struct blkfilter_operations - Block device filter operations.
+ *
+ * @link: Entry in the global list of filter drivers
+ * (must not be accessed by the driver).
+ * @owner: Module implementing the filter driver.
+ * @name: Name of the filter driver.
+ * @attach: Attach the filter driver to the block device.
+ * @detach: Detach the filter driver from the block device.
+ * @ctl: Send a control command to the filter driver.
+ * @submit_bio: Handle bio submissions to the filter driver.
+ */
+struct blkfilter_operations {
+ struct list_head link;
+ struct module *owner;
+ const char *name;
+ struct blkfilter *(*attach)(struct block_device *bdev);
+ void (*detach)(struct blkfilter *flt);
+ int (*ctl)(struct blkfilter *flt, const unsigned int cmd,
+ __u8 __user *buf, __u32 *plen);
+ bool (*submit_bio)(struct bio *bio);
+};
+
+int blkfilter_register(struct blkfilter_operations *ops);
+void blkfilter_unregister(struct blkfilter_operations *ops);
+
+#endif /* _UAPI_LINUX_BLK_FILTER_H */
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d5c5e59ddbd2..490865292fde 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -74,6 +74,7 @@ struct block_device {
* path
*/
struct device bd_device;
+ struct blkfilter *bd_filter;
} __randomize_layout;
#define bdev_whole(_bdev) \
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 51fa7ffdee83..6a0754007d1d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -834,6 +834,7 @@ void blk_request_module(dev_t devt);
extern int blk_register_queue(struct gendisk *disk);
extern void blk_unregister_queue(struct gendisk *disk);
+void submit_bio_noacct_nocheck(struct bio *bio);
void submit_bio_noacct(struct bio *bio);
struct bio *bio_split_to_limits(struct bio *bio);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 292c31697248..e7c3cd490a80 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1190,6 +1190,7 @@ struct task_struct {
/* Stack plugging: */
struct blk_plug *plug;
+ struct blkfilter *blk_filter;
/* VM state: */
struct reclaim_state *reclaim_state;
diff --git a/include/uapi/linux/blk-filter.h b/include/uapi/linux/blk-filter.h
new file mode 100644
index 000000000000..18885dc1b717
--- /dev/null
+++ b/include/uapi/linux/blk-filter.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (C) 2023 Veeam Software Group GmbH */
+#ifndef _UAPI_LINUX_BLK_FILTER_H
+#define _UAPI_LINUX_BLK_FILTER_H
+
+#include <linux/types.h>
+
+#define BLKFILTER_NAME_LENGTH 32
+
+/**
+ * struct blkfilter_name - parameter for BLKFILTER_ATTACH and BLKFILTER_DETACH
+ * ioctl.
+ *
+ * @name: Name of block device filter.
+ */
+struct blkfilter_name {
+ __u8 name[BLKFILTER_NAME_LENGTH];
+};
+
+/**
+ * struct blkfilter_ctl - parameter for BLKFILTER_CTL ioctl
+ *
+ * @name: Name of block device filter.
+ * @cmd: The filter-specific operation code of the command.
+ * @optlen: Size of data at @opt.
+ * @opt: Userspace buffer with options.
+ */
+struct blkfilter_ctl {
+ __u8 name[BLKFILTER_NAME_LENGTH];
+ __u32 cmd;
+ __u32 optlen;
+ __u64 opt;
+};
+
+#endif /* _UAPI_LINUX_BLK_FILTER_H */
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index da43810b7485..f96809cd2f50 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -189,6 +189,9 @@ struct fsxattr {
* A jump here: 130-136 are reserved for zoned block devices
* (see uapi/linux/blkzoned.h)
*/
+#define BLKFILTER_ATTACH _IOWR(0x12, 140, struct blkfilter_name)
+#define BLKFILTER_DETACH _IOWR(0x12, 141, struct blkfilter_name)
+#define BLKFILTER_CTL _IOWR(0x12, 142, struct blkfilter_ctl)
#define BMAP_IOCTL 1 /* obsolete - kept for compatibility */
#define FIBMAP _IO(0x00,1) /* bmap access */
--
2.20.1
> + struct request_queue *q = bdev_get_queue(bio->bi_bdev);
> + bool skip_bio = false;
> +
> + if (unlikely(bio_queue_enter(bio)))
> + return;
> +
> + if (bio->bi_bdev->bd_filter &&
> + bio->bi_bdev->bd_filter != current->blk_filter) {
> + struct blkfilter *prev = current->blk_filter;
> +
> + current->blk_filter = bio->bi_bdev->bd_filter;
> + skip_bio = bio->bi_bdev->bd_filter->ops->submit_bio(bio);
> + current->blk_filter = prev;
> + }
> +
> + blk_queue_exit(q);
This currently adds a queue enter/exit pair even if no filter driver
is used, which іs probably not acceptable. We probably need some
way to avoid the check in the fast path. In general an unlocked check
for bio->bi_bdev->bd_filter outside the protection seems fine to here,
we just need to find a good way to make sure it is visible by the
time a filter is actually set and the filter driver initialization.
> if (!bio->bi_bdev->bd_has_submit_bio) {
> blk_mq_submit_bio(bio);
> - } else if (likely(bio_queue_enter(bio) == 0)) {
> + return;
> + }
> +
> + if (likely(bio_queue_enter(bio) == 0)) {
This is just stray reformatting and we can drop it.
Hi Christoph.
Thanks for the review this patch set.
You've given me a good deal to think about.