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Message-ID: <20221209142331.26395-3-sergei.shtepa@veeam.com>
Date: Fri, 9 Dec 2022 15:23:12 +0100
From: Sergei Shtepa <sergei.shtepa@...am.com>
To: <axboe@...nel.dk>, <corbet@....net>
CC: <linux-block@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
Sergei Shtepa <sergei.shtepa@...am.com>
Subject: [PATCH v2 02/21] block, blkfilter: Block Device Filtering Mechanism
Allows to attach block device filters to the block devices. Kernel
modules can use this functionality to extend the capabilities of the
block layer.
Signed-off-by: Sergei Shtepa <sergei.shtepa@...am.com>
---
block/bdev.c | 70 ++++++++++++++++++++++++++++++++++++++
block/blk-core.c | 19 +++++++++--
include/linux/blk_types.h | 2 ++
include/linux/blkdev.h | 71 +++++++++++++++++++++++++++++++++++++++
4 files changed, 160 insertions(+), 2 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index d699ecdb3260..b820178824b2 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -427,6 +427,7 @@ static void init_once(void *data)
static void bdev_evict_inode(struct inode *inode)
{
+ bdev_filter_detach(I_BDEV(inode));
truncate_inode_pages_final(&inode->i_data);
invalidate_inode_buffers(inode); /* is it needed here? */
clear_inode(inode);
@@ -502,6 +503,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
return NULL;
}
bdev->bd_disk = disk;
+ bdev->bd_filter = NULL;
return bdev;
}
@@ -1092,3 +1094,71 @@ void bdev_statx_dioalign(struct inode *inode, struct kstat *stat)
blkdev_put_no_open(bdev);
}
+
+/**
+ * bdev_filter_attach - Attach the filter to the original block device.
+ * @bdev:
+ * Block device.
+ * @flt:
+ * Filter that needs to be attached to the block device.
+ *
+ * Before adding a filter, it is necessary to initialize &struct bdev_filter
+ * using a bdev_filter_init() function.
+ *
+ * The bdev_filter_detach() function allows to detach the filter from the block
+ * device.
+ *
+ * Return: 0 if succeeded, or -EALREADY if the filter already exists.
+ */
+int bdev_filter_attach(struct block_device *bdev,
+ struct bdev_filter *flt)
+{
+ int ret = 0;
+
+ blk_mq_freeze_queue(bdev->bd_queue);
+ blk_mq_quiesce_queue(bdev->bd_queue);
+
+ if (bdev->bd_filter)
+ ret = -EALREADY;
+ else
+ bdev->bd_filter = flt;
+
+ blk_mq_unquiesce_queue(bdev->bd_queue);
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+
+ return ret;
+}
+EXPORT_SYMBOL(bdev_filter_attach);
+
+/**
+ * bdev_filter_detach - Detach the filter from the block device.
+ * @bdev:
+ * Block device.
+ *
+ * The filter should be added using the bdev_filter_attach() function.
+ *
+ * Return: 0 if succeeded, or -ENOENT if the filter was not found.
+ */
+int bdev_filter_detach(struct block_device *bdev)
+{
+ int ret = 0;
+ struct bdev_filter *flt = NULL;
+
+ blk_mq_freeze_queue(bdev->bd_queue);
+ blk_mq_quiesce_queue(bdev->bd_queue);
+
+ flt = bdev->bd_filter;
+ if (flt)
+ bdev->bd_filter = NULL;
+ else
+ ret = -ENOENT;
+
+ blk_mq_unquiesce_queue(bdev->bd_queue);
+ blk_mq_unfreeze_queue(bdev->bd_queue);
+
+ if (flt)
+ bdev_filter_put(flt);
+
+ return ret;
+}
+EXPORT_SYMBOL(bdev_filter_detach);
diff --git a/block/blk-core.c b/block/blk-core.c
index 5487912befe8..284b295a7b23 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -678,9 +678,24 @@ void submit_bio_noacct_nocheck(struct bio *bio)
* to collect a list of requests submited by a ->submit_bio method while
* it is active, and then process them after it returned.
*/
- if (current->bio_list)
+ if (current->bio_list) {
bio_list_add(¤t->bio_list[0], bio);
- else if (!bio->bi_bdev->bd_disk->fops->submit_bio)
+ return;
+ }
+
+ if (bio->bi_bdev->bd_filter && !bio_flagged(bio, BIO_FILTERED)) {
+ bool pass;
+
+ pass = bio->bi_bdev->bd_filter->fops->submit_bio_cb(bio);
+ bio_set_flag(bio, BIO_FILTERED);
+ if (!pass) {
+ bio->bi_status = BLK_STS_OK;
+ bio_endio(bio);
+ return;
+ }
+ }
+
+ if (!bio->bi_bdev->bd_disk->fops->submit_bio)
__submit_bio_noacct_mq(bio);
else
__submit_bio_noacct(bio);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index e0b098089ef2..3b58c69cbf9d 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -68,6 +68,7 @@ struct block_device {
#ifdef CONFIG_FAIL_MAKE_REQUEST
bool bd_make_it_fail;
#endif
+ struct bdev_filter *bd_filter;
} __randomize_layout;
#define bdev_whole(_bdev) \
@@ -333,6 +334,7 @@ enum {
BIO_QOS_MERGED, /* but went through rq_qos merge path */
BIO_REMAPPED,
BIO_ZONE_WRITE_LOCKED, /* Owns a zoned device zone write lock */
+ BIO_FILTERED, /* bio has already been filtered */
BIO_FLAG_LAST
};
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 891f8cbcd043..dc2da4c7ab39 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1549,4 +1549,75 @@ struct io_comp_batch {
#define DEFINE_IO_COMP_BATCH(name) struct io_comp_batch name = { }
+/**
+ * struct bdev_filter_operations - Callback functions for the filter.
+ *
+ * @submit_bio_cb:
+ * A callback function for I/O unit handling.
+ * @release_cb:
+ * A callback function to disable the filter when removing a block
+ * device from the system.
+ */
+struct bdev_filter_operations {
+ bool (*submit_bio_cb)(struct bio *bio);
+ void (*release_cb)(struct kref *kref);
+};
+
+/**
+ * struct bdev_filter - Block device filter.
+ *
+ * @kref:
+ * Kernel reference counter.
+ * @fops:
+ * The pointer to &struct bdev_filter_operations with callback
+ * functions for the filter.
+ */
+struct bdev_filter {
+ struct kref kref;
+ const struct bdev_filter_operations *fops;
+};
+
+/**
+ * bdev_filter_init - Initialization of the filter structure.
+ * @flt:
+ * Pointer to the &struct bdev_filter to be initialized.
+ * @fops:
+ * The callback functions for the filter.
+ */
+static inline void bdev_filter_init(struct bdev_filter *flt,
+ const struct bdev_filter_operations *fops)
+{
+ kref_init(&flt->kref);
+ flt->fops = fops;
+};
+
+/**
+ * bdev_filter_get - Increment reference counter.
+ * @flt:
+ * Pointer to the &struct bdev_filter.
+ *
+ * Allows to ensure that the filter will not be released as long as there are
+ * references to it.
+ */
+static inline void bdev_filter_get(struct bdev_filter *flt)
+{
+ kref_get(&flt->kref);
+}
+
+/**
+ * bdev_filter_put - Decrement reference counter.
+ * @flt:
+ * Pointer to the &struct bdev_filter.
+ *
+ * Decrement the reference counter, and if 0, release filter.
+ */
+static inline void bdev_filter_put(struct bdev_filter *flt)
+{
+ kref_put(&flt->kref, flt->fops->release_cb);
+};
+
+int bdev_filter_attach(struct block_device *bdev, struct bdev_filter *flt);
+int bdev_filter_detach(struct block_device *bdev);
+
+
#endif /* _LINUX_BLKDEV_H */
--
2.20.1
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