[dm-devel] [PATCH 1/2] blk_interposer - Block Layer Interposer
Hannes Reinecke
hare at suse.de
Thu Nov 19 16:49:23 UTC 2020
From: Sergei Shtepa <sergei.shtepa at veeam.com>
The block layer interposer allows to intercept bio requests.
This allows you to connect device mapper and other kernel
modules to the block device stack on the fly.
Signed-off-by: Sergei Shtepa <sergei.shtepa at veeam.com>
Signed-off-by: Hannes Reinecke <hare at suse.de>
---
block/blk-core.c | 34 +++++++++++++++++++++++++++++
block/genhd.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/blk_types.h | 6 ++++--
include/linux/genhd.h | 19 ++++++++++++++++
4 files changed, 112 insertions(+), 2 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 2db8bda43b6e..130f0124d939 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1030,6 +1030,37 @@ static blk_qc_t __submit_bio_noacct_mq(struct bio *bio)
return ret;
}
+static blk_qc_t __submit_bio_interposed(struct bio *bio)
+{
+ struct bio_list bio_list[2] = { };
+ blk_qc_t ret = BLK_QC_T_NONE;
+
+ current->bio_list = bio_list;
+ if (likely(bio_queue_enter(bio) == 0)) {
+ struct gendisk *disk = bio->bi_disk;
+
+ bio_set_flag(bio, BIO_INTERPOSED);
+ if (likely(blk_has_interposer(disk))) {
+ struct blk_interposer *ip = disk->interposer;
+ ret = ip->ip_submit_bio(ip, bio);
+
+ if (ret == BLK_QC_T_NONE)
+ blk_queue_exit(disk->queue);
+ } else {
+ /* interposer was removed */
+ bio_list_add(¤t->bio_list[0], bio);
+ blk_queue_exit(bio->bi_disk->queue);
+ }
+ }
+ current->bio_list = NULL;
+
+ /* Resubmit remaining bios */
+ while ((bio = bio_list_pop(&bio_list[0])))
+ ret = submit_bio_noacct(bio);
+
+ return ret;
+}
+
/**
* submit_bio_noacct - re-submit a bio to the block device layer for I/O
* @bio: The bio describing the location in memory and on the device.
@@ -1055,6 +1086,9 @@ blk_qc_t submit_bio_noacct(struct bio *bio)
return BLK_QC_T_NONE;
}
+ if (blk_has_interposer(bio->bi_disk) &&
+ !bio_flagged(bio, BIO_INTERPOSED))
+ return __submit_bio_interposed(bio);
if (!bio->bi_disk->fops->submit_bio)
return __submit_bio_noacct_mq(bio);
return __submit_bio_noacct(bio);
diff --git a/block/genhd.c b/block/genhd.c
index 9387f050c248..17b43e2ed06a 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -2364,3 +2364,58 @@ static void disk_release_events(struct gendisk *disk)
WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
kfree(disk->ev);
}
+
+/**
+ * blk_interposer_attach - Attach interposer to disk
+ * @disk: target disk
+ * @interposer: block device interposer
+ *
+ * Returns:
+ * -EINVAL if @interposer is NULL.
+ * -ENODEV if interposer is not initialized,
+ * -EBUSY if the block device already has interposer.
+ */
+int blk_interposer_attach(struct gendisk *disk,
+ struct blk_interposer *interposer)
+{
+ int ret = 0;
+
+ if (!interposer)
+ return -EINVAL;
+
+ blk_mq_freeze_queue(disk->queue);
+ blk_mq_quiesce_queue(disk->queue);
+ if (blk_has_interposer(disk))
+ ret = -EBUSY;
+ else
+ disk->interposer = interposer;
+ blk_mq_unquiesce_queue(disk->queue);
+ blk_mq_unfreeze_queue(disk->queue);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blk_interposer_attach);
+
+/**
+ * blk_interposer_detach - Detach interposer from disk
+ * @disk: target disk
+ *
+ * Returns the attached interposer or NULL if none was attached.
+ */
+struct blk_interposer *blk_interposer_detach(struct gendisk *disk)
+{
+ struct blk_interposer *interposer;
+
+ if (WARN_ON(!disk))
+ return NULL;
+
+ blk_mq_freeze_queue(disk->queue);
+ blk_mq_quiesce_queue(disk->queue);
+ interposer = disk->interposer;
+ disk->interposer = NULL;
+ blk_mq_unquiesce_queue(disk->queue);
+ blk_mq_unfreeze_queue(disk->queue);
+
+ return interposer;
+}
+EXPORT_SYMBOL_GPL(blk_interposer_detach);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d9b69bbde5cc..996b803e5aa1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -207,7 +207,7 @@ struct bio {
* top bits REQ_OP. Use
* accessors.
*/
- unsigned short bi_flags; /* status, etc and bvec pool number */
+ unsigned int bi_flags; /* status, etc and bvec pool number */
unsigned short bi_ioprio;
unsigned short bi_write_hint;
blk_status_t bi_status;
@@ -284,6 +284,8 @@ enum {
* of this bio. */
BIO_CGROUP_ACCT, /* has been accounted to a cgroup */
BIO_TRACKED, /* set if bio goes through the rq_qos path */
+ BIO_INTERPOSED, /* bio has been interposed and can be moved to
+ * a different disk */
BIO_FLAG_LAST
};
@@ -302,7 +304,7 @@ enum {
* freed.
*/
#define BVEC_POOL_BITS (3)
-#define BVEC_POOL_OFFSET (16 - BVEC_POOL_BITS)
+#define BVEC_POOL_OFFSET (32 - BVEC_POOL_BITS)
#define BVEC_POOL_IDX(bio) ((bio)->bi_flags >> BVEC_POOL_OFFSET)
#if (1<< BVEC_POOL_BITS) < (BVEC_POOL_NR+1)
# error "BVEC_POOL_BITS is too small"
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 03da3f603d30..f58ab391deda 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -164,6 +164,15 @@ struct blk_integrity {
unsigned char tag_size;
};
+struct blk_interposer;
+typedef blk_qc_t (*ip_submit_bio_t) (struct blk_interposer *ip, struct bio *bio);
+
+struct blk_interposer {
+ struct gendisk *ip_disk;
+ ip_submit_bio_t ip_submit_bio;
+ void *ip_private;
+};
+
struct gendisk {
/* major, first_minor and minors are input parameters only,
* don't use directly. Use disk_devt() and disk_max_parts().
@@ -188,6 +197,7 @@ struct gendisk {
const struct block_device_operations *fops;
struct request_queue *queue;
+ struct blk_interposer *interposer;
void *private_data;
int flags;
@@ -409,4 +419,13 @@ static inline dev_t blk_lookup_devt(const char *name, int partno)
}
#endif /* CONFIG_BLOCK */
+/*
+ * Block device interposing
+ */
+#define blk_has_interposer(d) ((d)->interposer != NULL)
+#define blk_interposer_active(ip) ((ip)->ip_disk != NULL)
+
+int blk_interposer_attach(struct gendisk *, struct blk_interposer *);
+struct blk_interposer * blk_interposer_detach(struct gendisk *);
+
#endif /* _LINUX_GENHD_H */
--
2.16.4
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