[PATCH 0/3] bcachefs block layer prereqs

[PATCH 0/3] bcachefs block layer prereqs

[Kent Overstreet]

Hi Jens, here's the (hopefully final) bcachefs block layer prereqs,
aiming for v6.6.

The "block: Don't block on s_umount from __invalidate_super()" patch has
been dropped for now - but we may want this later as there's a real bug
it addresses, and with the blockdev holder changes now landing I suspect
other filesystems will be hitting the same issue as bcachefs.

But that can be a topic for another thread.

Can I get either acks or have you take them via your tree, your
preference?

Kent Overstreet (3):
  block: Add some exports for bcachefs
  block: Allow bio_iov_iter_get_pages() with bio->bi_bdev unset
  block: Bring back zero_fill_bio_iter

 block/bio.c            | 18 +++++++++++-------
 block/blk-core.c       |  1 +
 block/blk.h            |  1 -
 include/linux/bio.h    |  7 ++++++-
 include/linux/blkdev.h |  1 +
 5 files changed, 19 insertions(+), 9 deletions(-)

-- 
2.40.1

[PATCH 1/3] block: Add some exports for bcachefs

[Kent Overstreet]

From: Kent Overstreet <kent.overstreet@gmail.com>

 - bio_set_pages_dirty(), bio_check_pages_dirty() - dio path
 - blk_status_to_str() - error messages
 - bio_add_folio() - this should definitely be exported for everyone,
   it's the modern version of bio_add_page()

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 block/bio.c            | 2 ++
 block/blk-core.c       | 1 +
 block/blk.h            | 1 -
 include/linux/blkdev.h | 1 +
 4 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 043944fd46..1e75840d17 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1481,6 +1481,7 @@ void bio_set_pages_dirty(struct bio *bio)
 			set_page_dirty_lock(bvec->bv_page);
 	}
 }
+EXPORT_SYMBOL_GPL(bio_set_pages_dirty);
 
 /*
  * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
@@ -1540,6 +1541,7 @@ void bio_check_pages_dirty(struct bio *bio)
 	spin_unlock_irqrestore(&bio_dirty_lock, flags);
 	schedule_work(&bio_dirty_work);
 }
+EXPORT_SYMBOL_GPL(bio_check_pages_dirty);
 
 static inline bool bio_remaining_done(struct bio *bio)
 {
diff --git a/block/blk-core.c b/block/blk-core.c
index 1da77e7d62..b7b0237c36 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -205,6 +205,7 @@ const char *blk_status_to_str(blk_status_t status)
 		return "<null>";
 	return blk_errors[idx].name;
 }
+EXPORT_SYMBOL_GPL(blk_status_to_str);
 
 /**
  * blk_sync_queue - cancel any pending callbacks on a queue
diff --git a/block/blk.h b/block/blk.h
index 45547bcf11..f20f9ca03e 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -251,7 +251,6 @@ static inline void bio_integrity_free(struct bio *bio)
 
 unsigned long blk_rq_timeout(unsigned long timeout);
 void blk_add_timer(struct request *req);
-const char *blk_status_to_str(blk_status_t status);
 
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c0ffe203a6..7a32dc98e1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -854,6 +854,7 @@ extern const char *blk_op_str(enum req_op op);
 
 int blk_status_to_errno(blk_status_t status);
 blk_status_t errno_to_blk_status(int errno);
+const char *blk_status_to_str(blk_status_t status);
 
 /* only poll the hardware once, don't continue until a completion was found */
 #define BLK_POLL_ONESHOT		(1 << 0)
-- 
2.40.1

[PATCH 2/3] block: Allow bio_iov_iter_get_pages() with bio->bi_bdev unset

[Kent Overstreet]

bio_iov_iter_get_pages() trims the IO based on the block size of the
block device the IO will be issued to.

However, bcachefs is a multi device filesystem; when we're creating the
bio we don't yet know which block device the bio will be submitted to -
we have to handle the alignment checks elsewhere.

Thus this is needed to avoid a null ptr deref.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
---
 block/bio.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 1e75840d17..e74a04ea14 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1245,7 +1245,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	struct page **pages = (struct page **)bv;
 	ssize_t size, left;
 	unsigned len, i = 0;
-	size_t offset, trim;
+	size_t offset;
 	int ret = 0;
 
 	/*
@@ -1274,10 +1274,12 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 
 	nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
 
-	trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
-	iov_iter_revert(iter, trim);
+	if (bio->bi_bdev) {
+		size_t trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
+		iov_iter_revert(iter, trim);
+		size -= trim;
+	}
 
-	size -= trim;
 	if (unlikely(!size)) {
 		ret = -EFAULT;
 		goto out;
-- 
2.40.1

[PATCH 3/3] block: Bring back zero_fill_bio_iter

[Kent Overstreet]

From: Kent Overstreet <kent.overstreet@gmail.com>

This reverts 6f822e1b5d9dda3d20e87365de138046e3baa03a - this helper is
used by bcachefs.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
---
 block/bio.c         | 6 +++---
 include/linux/bio.h | 7 ++++++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index e74a04ea14..70b5c987bc 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -606,15 +606,15 @@ struct bio *bio_kmalloc(unsigned short nr_vecs, gfp_t gfp_mask)
 }
 EXPORT_SYMBOL(bio_kmalloc);
 
-void zero_fill_bio(struct bio *bio)
+void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
 {
 	struct bio_vec bv;
 	struct bvec_iter iter;
 
-	bio_for_each_segment(bv, bio, iter)
+	__bio_for_each_segment(bv, bio, iter, start)
 		memzero_bvec(&bv);
 }
-EXPORT_SYMBOL(zero_fill_bio);
+EXPORT_SYMBOL(zero_fill_bio_iter);
 
 /**
  * bio_truncate - truncate the bio to small size of @new_size
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b3e7529ff5..f2620f8d18 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -484,7 +484,12 @@ extern void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
 extern void bio_copy_data(struct bio *dst, struct bio *src);
 extern void bio_free_pages(struct bio *bio);
 void guard_bio_eod(struct bio *bio);
-void zero_fill_bio(struct bio *bio);
+void zero_fill_bio_iter(struct bio *bio, struct bvec_iter iter);
+
+static inline void zero_fill_bio(struct bio *bio)
+{
+	zero_fill_bio_iter(bio, bio->bi_iter);
+}
 
 static inline void bio_release_pages(struct bio *bio, bool mark_dirty)
 {
-- 
2.40.1

Re: [PATCH 0/3] bcachefs block layer prereqs

[Jens Axboe]

On Sun, 13 Aug 2023 14:26:33 -0400, Kent Overstreet wrote:
> aiming for v6.6.
> 
> The "block: Don't block on s_umount from __invalidate_super()" patch has
> been dropped for now - but we may want this later as there's a real bug
> it addresses, and with the blockdev holder changes now landing I suspect
> other filesystems will be hitting the same issue as bcachefs.
> 
> [...]

Applied, thanks!

[1/3] block: Add some exports for bcachefs
      commit: 7ba3792718709d410be5d971732b9251cbda67b6
[2/3] block: Allow bio_iov_iter_get_pages() with bio->bi_bdev unset
      commit: 168145f617d57bf4e474901b7ffa869337a802e6
[3/3] block: Bring back zero_fill_bio_iter
      commit: 649f070e69739d22c57c22dbce0788b72cd93fac

Best regards,
-- 
Jens Axboe