Re: [PATCH v6 2/4] block: add blk_interposer
From: Christoph Hellwig <hch@infradead.org>
Date: 2021-03-09 17:28:44
Also in:
dm-devel, linux-api, linux-raid, lkml
quoted hunk ↗ jump to hunk
+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 block_device *bdev = bio->bi_bdev; + + if (likely(bdev_has_interposer(bdev))) { + bio_set_flag(bio, BIO_INTERPOSED); + bdev->bd_interposer->ip_submit_bio(bio); + } else { + /* interposer was removed */ + bio_list_add(¤t->bio_list[0], bio); + } + + blk_queue_exit(bdev->bd_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.@@ -1043,6 +1071,14 @@ blk_qc_t submit_bio_noacct(struct bio *bio) return BLK_QC_T_NONE; } + /* + * Checking the BIO_INTERPOSED flag is necessary so that the bio + * created by the bdev_interposer do not get to it for processing. + */ + if (bdev_has_interposer(bio->bi_bdev) && + !bio_flagged(bio, BIO_INTERPOSED)) + return __submit_bio_interposed(bio); + if (!bio->bi_bdev->bd_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 fcc530164b5a..1ae8516643c8 100644 --- a/block/genhd.c +++ b/block/genhd.c@@ -30,6 +30,11 @@ static struct kobject *block_depr; DECLARE_RWSEM(bdev_lookup_sem); +/* + * Prevents different block-layer interposers from attaching or detaching + * to the block device at the same time. + */ +DEFINE_MUTEX(bdev_interposer_attach_lock);
This one can and should be marked static.
+int bdev_interposer_attach(struct block_device *bdev, struct bdev_interposer *interposer,
Please avoid the overly long line.
+ int ret = 0; + + if (WARN_ON(!interposer))
WARN_ON_ONCE?
+ return -EINVAL; + + if (!blk_mq_is_queue_frozen(bdev->bd_disk->queue)) + return -EPERM;
This probly should be a WARN_ON_ONCE() as well.
+
+ mutex_lock(&bdev_interposer_attach_lock);
+ if (bdev_has_interposer(bdev)) {
+ if (bdev->bd_interposer->ip_submit_bio == ip_submit_bio)
+ ret = -EALREADY;
+ else
+ ret = -EBUSY;
+ goto out;
+ }Do we really need the two different error codes here?
+ + interposer->ip_submit_bio = ip_submit_bio;
I'd rather let the caller initialize the field instead of passing the submit function separately.
+void bdev_interposer_detach(struct bdev_interposer *interposer,
+ const ip_submit_bio_t ip_submit_bio)
+{+ /* Check if it is really our interposer. */ + if (WARN_ON(bdev->bd_interposer->ip_submit_bio != ip_submit_bio)) + goto out;
I don't really see any need to pass ip_submit_bio just for this check.
+ struct bdev_interposer * bd_interposer;
The * goes just before the member name.
+/*
+ * block layer interposers structure and functions
+ */
+typedef void (*ip_submit_bio_t) (struct bio *bio);
+
+struct bdev_interposer {
+ ip_submit_bio_t ip_submit_bio;
+ struct block_device *bdev;Do we need the ip_ prefix here? Also we probably don't really the the typedef for the function pointer.
+#define bdev_has_interposer(bd) ((bd)->bd_interposer != NULL)
And inline function would be nice here.