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Message-ID: <ZVx5XE3o+D8pGPib@fedora>
Date: Tue, 21 Nov 2023 17:33:16 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, yukuai3@...wei.com,
yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2 1/2] block: introduce new field flags in block_device
On Tue, Nov 21, 2023 at 07:19:26PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
>
> There are multiple switches in struct block_device, use separate bool
> fields for them is not gracefully. Add a new field flags and replace
> swithes to a bit, there are no functional changes, and preare to add
> a new switch in the next patch.
>
> In order to keep flags in the first cacheline, define it as u32 and add
> new helpers to set/clear/test each bit like 'bio->bi_flags'.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> block/bdev.c | 15 ++++++++-------
> block/blk-core.c | 7 ++++---
> block/genhd.c | 15 +++++++++++----
> block/ioctl.c | 6 +++++-
> include/linux/blk_types.h | 27 +++++++++++++++++++++------
> include/linux/blkdev.h | 5 +++--
> 6 files changed, 52 insertions(+), 23 deletions(-)
>
> diff --git a/block/bdev.c b/block/bdev.c
> index fc8d28d77495..6b420cbd4f3d 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -408,10 +408,10 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
> bdev->bd_partno = partno;
> bdev->bd_inode = inode;
> bdev->bd_queue = disk->queue;
> - if (partno)
> - bdev->bd_has_submit_bio = disk->part0->bd_has_submit_bio;
> + if (partno && bdev_flagged(disk->part0, BD_FLAG_HAS_SUBMIT_BIO))
> + bdev_set_flag(bdev, BD_FLAG_HAS_SUBMIT_BIO);
> else
> - bdev->bd_has_submit_bio = false;
> + bdev_clear_flag(bdev, BD_FLAG_HAS_SUBMIT_BIO);
> bdev->bd_stats = alloc_percpu(struct disk_stats);
> if (!bdev->bd_stats) {
> iput(inode);
> @@ -612,7 +612,7 @@ static void bd_end_claim(struct block_device *bdev, void *holder)
> bdev->bd_holder = NULL;
> bdev->bd_holder_ops = NULL;
> mutex_unlock(&bdev->bd_holder_lock);
> - if (bdev->bd_write_holder)
> + if (bdev_flagged(bdev, BD_FLAG_WRITE_HOLDER))
> unblock = true;
> }
> if (!whole->bd_holders)
> @@ -625,7 +625,7 @@ static void bd_end_claim(struct block_device *bdev, void *holder)
> */
> if (unblock) {
> disk_unblock_events(bdev->bd_disk);
> - bdev->bd_write_holder = false;
> + bdev_clear_flag(bdev, BD_FLAG_WRITE_HOLDER);
> }
> }
>
> @@ -878,9 +878,10 @@ struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
> * writeable reference is too fragile given the way @mode is
> * used in blkdev_get/put().
> */
> - if ((mode & BLK_OPEN_WRITE) && !bdev->bd_write_holder &&
> + if ((mode & BLK_OPEN_WRITE) &&
> + !bdev_flagged(bdev, BD_FLAG_WRITE_HOLDER) &&
> (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
> - bdev->bd_write_holder = true;
> + bdev_set_flag(bdev, BD_FLAG_WRITE_HOLDER);
> unblock_events = false;
> }
> }
> diff --git a/block/blk-core.c b/block/blk-core.c
> index fdf25b8d6e78..f9f8b12ba626 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -482,7 +482,8 @@ __setup("fail_make_request=", setup_fail_make_request);
>
> bool should_fail_request(struct block_device *part, unsigned int bytes)
> {
> - return part->bd_make_it_fail && should_fail(&fail_make_request, bytes);
> + return bdev_flagged(part, BD_FLAG_MAKE_IT_FAIL) &&
> + should_fail(&fail_make_request, bytes);
> }
>
> static int __init fail_make_request_debugfs(void)
> @@ -595,7 +596,7 @@ static void __submit_bio(struct bio *bio)
> if (unlikely(!blk_crypto_bio_prep(&bio)))
> return;
>
> - if (!bio->bi_bdev->bd_has_submit_bio) {
> + if (!bdev_flagged(bio->bi_bdev, BD_FLAG_HAS_SUBMIT_BIO)) {
> blk_mq_submit_bio(bio);
> } else if (likely(bio_queue_enter(bio) == 0)) {
> struct gendisk *disk = bio->bi_bdev->bd_disk;
> @@ -703,7 +704,7 @@ void submit_bio_noacct_nocheck(struct bio *bio)
> */
> if (current->bio_list)
> bio_list_add(¤t->bio_list[0], bio);
> - else if (!bio->bi_bdev->bd_has_submit_bio)
> + else if (!bdev_flagged(bio->bi_bdev, BD_FLAG_HAS_SUBMIT_BIO))
> __submit_bio_noacct_mq(bio);
> else
> __submit_bio_noacct(bio);
> diff --git a/block/genhd.c b/block/genhd.c
> index c9d06f72c587..57f96c0c8da0 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -413,7 +413,8 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
> elevator_init_mq(disk->queue);
>
> /* Mark bdev as having a submit_bio, if needed */
> - disk->part0->bd_has_submit_bio = disk->fops->submit_bio != NULL;
> + if (disk->fops->submit_bio)
> + bdev_set_flag(disk->part0, BD_FLAG_HAS_SUBMIT_BIO);
>
> /*
> * If the driver provides an explicit major number it also must provide
> @@ -1062,7 +1063,8 @@ static DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
> ssize_t part_fail_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> - return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_make_it_fail);
> + return sprintf(buf, "%d\n",
> + bdev_flagged(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL));
> }
>
> ssize_t part_fail_store(struct device *dev,
> @@ -1071,8 +1073,13 @@ ssize_t part_fail_store(struct device *dev,
> {
> int i;
>
> - if (count > 0 && sscanf(buf, "%d", &i) > 0)
> - dev_to_bdev(dev)->bd_make_it_fail = i;
> + if (count > 0 && sscanf(buf, "%d", &i) > 0) {
> + if (!i)
> + bdev_clear_flag(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL);
> + else
> + bdev_set_flag(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL);
> +
> + }
>
> return count;
> }
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 4160f4e6bd5b..a64440f4c96b 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -394,7 +394,11 @@ static int blkdev_roset(struct block_device *bdev, unsigned cmd,
> if (ret)
> return ret;
> }
> - bdev->bd_read_only = n;
> +
> + if (!n)
> + bdev_clear_flag(bdev, BD_FLAG_READ_ONLY);
> + else
> + bdev_set_flag(bdev, BD_FLAG_READ_ONLY);
> return 0;
> }
>
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 52e264d5a830..f7a7965eeb25 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -37,6 +37,11 @@ struct bio_crypt_ctx;
> #define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
> #define SECTOR_MASK (PAGE_SECTORS - 1)
>
> +#define BD_FLAG_READ_ONLY 0 /* read-only-policy */
> +#define BD_FLAG_WRITE_HOLDER 1
> +#define BD_FLAG_HAS_SUBMIT_BIO 2
> +#define BD_FLAG_MAKE_IT_FAIL 3
> +
> struct block_device {
> sector_t bd_start_sect;
> sector_t bd_nr_sectors;
> @@ -44,10 +49,8 @@ struct block_device {
> struct request_queue * bd_queue;
> struct disk_stats __percpu *bd_stats;
> unsigned long bd_stamp;
> - bool bd_read_only; /* read-only policy */
> + unsigned int bd_flags;
> u8 bd_partno;
> - bool bd_write_holder;
> - bool bd_has_submit_bio;
> dev_t bd_dev;
> atomic_t bd_openers;
> spinlock_t bd_size_lock; /* for bd_inode->i_size updates */
As I mentioned, you can convert the above/original 4 fields into single
'unsigned int', otherwise one extra 'int' filed is added. Then, 'bd_size_lock'
is moved to the 2nd cache line, which isn't big deal since the field isn't
touched in fast path. Anyway, it can be one future cleanup, so:
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Thanks,
Ming
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