Commit 3222d8c2 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Andrew Morton
Browse files

block: remove ->rw_page 

The ->rw_page method is a special purpose bypass of the usual bio handling
path that is limited to single-page reads and writes and synchronous which
causes a lot of extra code in the drivers, callers and the block layer.

The only remaining user is the MM swap code.  Switch that swap code to
simply submit a single-vec on-stack bio an synchronously wait on it based
on a newly added QUEUE_FLAG_SYNCHRONOUS flag set by the drivers that
currently implement ->rw_page instead.  While this touches one extra cache
line and executes extra code, it simplifies the block layer and drivers
and ensures that all feastures are properly supported by all drivers, e.g.
right now ->rw_page bypassed cgroup writeback entirely.

[akpm@linux-foundation.org: fix comment typo, per Dan]
Link: https://lkml.kernel.org/r/20230125133436.447864-8-hch@lst.de


Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 05cda97e

block/bdev.c

+0 −78
Original line number Diff line number Diff line
@@ -304,84 +304,6 @@ int thaw_bdev(struct block_device *bdev) 
}

EXPORT_SYMBOL(thaw_bdev);



/**

 * bdev_read_page() - Start reading a page from a block device

 * @bdev: The device to read the page from

 * @sector: The offset on the device to read the page to (need not be aligned)

 * @page: The page to read

 *

 * On entry, the page should be locked.  It will be unlocked when the page

 * has been read.  If the block driver implements rw_page synchronously,

 * that will be true on exit from this function, but it need not be.

 *

 * Errors returned by this function are usually "soft", eg out of memory, or

 * queue full; callers should try a different route to read this page rather

 * than propagate an error back up the stack.

 *

 * Return: negative errno if an error occurs, 0 if submission was successful.

 */

int bdev_read_page(struct block_device *bdev, sector_t sector,

			struct page *page)

{

	const struct block_device_operations *ops = bdev->bd_disk->fops;

	int result = -EOPNOTSUPP;



	if (!ops->rw_page || bdev_get_integrity(bdev))

		return result;



	result = blk_queue_enter(bdev_get_queue(bdev), 0);

	if (result)

		return result;

	result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,

			      REQ_OP_READ);

	blk_queue_exit(bdev_get_queue(bdev));

	return result;

}



/**

 * bdev_write_page() - Start writing a page to a block device

 * @bdev: The device to write the page to

 * @sector: The offset on the device to write the page to (need not be aligned)

 * @page: The page to write

 * @wbc: The writeback_control for the write

 *

 * On entry, the page should be locked and not currently under writeback.

 * On exit, if the write started successfully, the page will be unlocked and

 * under writeback.  If the write failed already (eg the driver failed to

 * queue the page to the device), the page will still be locked.  If the

 * caller is a ->writepage implementation, it will need to unlock the page.

 *

 * Errors returned by this function are usually "soft", eg out of memory, or

 * queue full; callers should try a different route to write this page rather

 * than propagate an error back up the stack.

 *

 * Return: negative errno if an error occurs, 0 if submission was successful.

 */

int bdev_write_page(struct block_device *bdev, sector_t sector,

			struct page *page, struct writeback_control *wbc)

{

	int result;

	const struct block_device_operations *ops = bdev->bd_disk->fops;



	if (!ops->rw_page || bdev_get_integrity(bdev))

		return -EOPNOTSUPP;

	result = blk_queue_enter(bdev_get_queue(bdev), 0);

	if (result)

		return result;



	set_page_writeback(page);

	result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,

			      REQ_OP_WRITE);

	if (result) {

		end_page_writeback(page);

	} else {

		clean_page_buffers(page);

		unlock_page(page);

	}

	blk_queue_exit(bdev_get_queue(bdev));

	return result;

}



/*

 * pseudo-fs

 */

drivers/block/brd.c

+1 −14
Original line number Diff line number Diff line
@@ -309,23 +309,9 @@ static void brd_submit_bio(struct bio *bio) 
	bio_endio(bio);

}



static int brd_rw_page(struct block_device *bdev, sector_t sector,

		       struct page *page, enum req_op op)

{

	struct brd_device *brd = bdev->bd_disk->private_data;

	int err;



	if (PageTransHuge(page))

		return -ENOTSUPP;

	err = brd_do_bvec(brd, page, PAGE_SIZE, 0, op, sector);

	page_endio(page, op_is_write(op), err);

	return err;

}



static const struct block_device_operations brd_fops = {

	.owner =		THIS_MODULE,

	.submit_bio =		brd_submit_bio,

	.rw_page =		brd_rw_page,

};



/*
@@ -411,6 +397,7 @@ static int brd_alloc(int i) 


	/* Tell the block layer that this is not a rotational device */

	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);

	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, disk->queue);

	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);

	err = add_disk(disk);

	if (err)

drivers/block/zram/zram_drv.c

+1 −60
Original line number Diff line number Diff line
@@ -1453,10 +1453,6 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index, 
		/* Slot should be unlocked before the function call */

		zram_slot_unlock(zram, index);



		/* A null bio means rw_page was used, we must fallback to bio */

		if (!bio)

			return -EOPNOTSUPP;



		ret = zram_bvec_read_from_bdev(zram, page, index, bio,

					       partial_io);

	}
@@ -2081,61 +2077,6 @@ static void zram_slot_free_notify(struct block_device *bdev, 
	zram_slot_unlock(zram, index);

}



static int zram_rw_page(struct block_device *bdev, sector_t sector,

		       struct page *page, enum req_op op)

{

	int offset, ret;

	u32 index;

	struct zram *zram;

	struct bio_vec bv;

	unsigned long start_time;



	if (PageTransHuge(page))

		return -ENOTSUPP;

	zram = bdev->bd_disk->private_data;



	if (!valid_io_request(zram, sector, PAGE_SIZE)) {

		atomic64_inc(&zram->stats.invalid_io);

		ret = -EINVAL;

		goto out;

	}



	index = sector >> SECTORS_PER_PAGE_SHIFT;

	offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;



	bv.bv_page = page;

	bv.bv_len = PAGE_SIZE;

	bv.bv_offset = 0;



	start_time = bdev_start_io_acct(bdev->bd_disk->part0,

			SECTORS_PER_PAGE, op, jiffies);

	ret = zram_bvec_rw(zram, &bv, index, offset, op, NULL);

	bdev_end_io_acct(bdev->bd_disk->part0, op, start_time);

out:

	/*

	 * If I/O fails, just return error(ie, non-zero) without

	 * calling page_endio.

	 * It causes resubmit the I/O with bio request by upper functions

	 * of rw_page(e.g., swap_readpage, __swap_writepage) and

	 * bio->bi_end_io does things to handle the error

	 * (e.g., SetPageError, set_page_dirty and extra works).

	 */

	if (unlikely(ret < 0))

		return ret;



	switch (ret) {

	case 0:

		page_endio(page, op_is_write(op), 0);

		break;

	case 1:

		ret = 0;

		break;

	default:

		WARN_ON(1);

	}

	return ret;

}



static void zram_destroy_comps(struct zram *zram)

{

	u32 prio;
@@ -2290,7 +2231,6 @@ static const struct block_device_operations zram_devops = { 
	.open = zram_open,

	.submit_bio = zram_submit_bio,

	.swap_slot_free_notify = zram_slot_free_notify,

	.rw_page = zram_rw_page,

	.owner = THIS_MODULE

};
@@ -2389,6 +2329,7 @@ static int zram_add(void) 
	set_capacity(zram->disk, 0);

	/* zram devices sort of resembles non-rotational disks */

	blk_queue_flag_set(QUEUE_FLAG_NONROT, zram->disk->queue);

	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, zram->disk->queue);

	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);



	/*

drivers/nvdimm/btt.c

+1 −15
Original line number Diff line number Diff line
@@ -1482,20 +1482,6 @@ static void btt_submit_bio(struct bio *bio) 
	bio_endio(bio);

}



static int btt_rw_page(struct block_device *bdev, sector_t sector,

		struct page *page, enum req_op op)

{

	struct btt *btt = bdev->bd_disk->private_data;

	int rc;



	rc = btt_do_bvec(btt, NULL, page, thp_size(page), 0, op, sector);

	if (rc == 0)

		page_endio(page, op_is_write(op), 0);



	return rc;

}





static int btt_getgeo(struct block_device *bd, struct hd_geometry *geo)

{

	/* some standard values */
@@ -1508,7 +1494,6 @@ static int btt_getgeo(struct block_device *bd, struct hd_geometry *geo) 
static const struct block_device_operations btt_fops = {

	.owner =		THIS_MODULE,

	.submit_bio =		btt_submit_bio,

	.rw_page =		btt_rw_page,

	.getgeo =		btt_getgeo,

};
@@ -1530,6 +1515,7 @@ static int btt_blk_init(struct btt *btt) 
	blk_queue_logical_block_size(btt->btt_disk->queue, btt->sector_size);

	blk_queue_max_hw_sectors(btt->btt_disk->queue, UINT_MAX);

	blk_queue_flag_set(QUEUE_FLAG_NONROT, btt->btt_disk->queue);

	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, btt->btt_disk->queue);



	if (btt_meta_size(btt)) {

		rc = nd_integrity_init(btt->btt_disk, btt_meta_size(btt));

drivers/nvdimm/pmem.c

+1 −23
Original line number Diff line number Diff line
@@ -238,28 +238,6 @@ static void pmem_submit_bio(struct bio *bio) 
	bio_endio(bio);

}



static int pmem_rw_page(struct block_device *bdev, sector_t sector,

		       struct page *page, enum req_op op)

{

	struct pmem_device *pmem = bdev->bd_disk->private_data;

	blk_status_t rc;



	if (op_is_write(op))

		rc = pmem_do_write(pmem, page, 0, sector, thp_size(page));

	else

		rc = pmem_do_read(pmem, page, 0, sector, thp_size(page));

	/*

	 * The ->rw_page interface is subtle and tricky.  The core

	 * retries on any error, so we can only invoke page_endio() in

	 * the successful completion case.  Otherwise, we'll see crashes

	 * caused by double completion.

	 */

	if (rc == 0)

		page_endio(page, op_is_write(op), 0);



	return blk_status_to_errno(rc);

}



/* see "strong" declaration in tools/testing/nvdimm/pmem-dax.c */

__weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,

		long nr_pages, enum dax_access_mode mode, void **kaddr,
@@ -310,7 +288,6 @@ __weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff, 
static const struct block_device_operations pmem_fops = {

	.owner =		THIS_MODULE,

	.submit_bio =		pmem_submit_bio,

	.rw_page =		pmem_rw_page,

};



static int pmem_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
@@ -565,6 +542,7 @@ static int pmem_attach_disk(struct device *dev, 
	blk_queue_logical_block_size(q, pmem_sector_size(ndns));

	blk_queue_max_hw_sectors(q, UINT_MAX);

	blk_queue_flag_set(QUEUE_FLAG_NONROT, q);

	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, q);

	if (pmem->pfn_flags & PFN_MAP)

		blk_queue_flag_set(QUEUE_FLAG_DAX, q);