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Date: Mon, 20 Nov 2023 16:01:03 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Ming Lei <ming.lei@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH 1/2] block: introduce new field flags in block_device
Hi,
在 2023/11/20 11:00, Ming Lei 写道:
> On Mon, Nov 20, 2023 at 05:38:46PM +0800, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> There are multiple switches in struct block_device, use seperate bool
>> fields for them is not gracefully. Add a new field flags and replace
>> swithes to a bit, there are no functional changes, and preapre to add
>> a new switch in the next patch.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> block/bdev.c | 15 ++++++++-------
>> block/blk-core.c | 7 ++++---
>> block/genhd.c | 8 +++++---
>> block/ioctl.c | 2 +-
>> include/linux/blk_types.h | 12 ++++++------
>> include/linux/blkdev.h | 5 +++--
>> 6 files changed, 27 insertions(+), 22 deletions(-)
>>
>> diff --git a/block/bdev.c b/block/bdev.c
>> index fc8d28d77495..cb849bcf61ae 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 && test_bit(BD_FLAG_HAS_SUBMIT_BIO, &disk->part0->flags))
>> + set_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
>> else
>> - bdev->bd_has_submit_bio = false;
>> + clear_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
>> 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 (test_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags))
>> 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;
>> + clear_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags);
>> }
>> }
>>
>> @@ -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) &&
>> + !test_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags) &&
>> (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
>> - bdev->bd_write_holder = true;
>> + set_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags);
>> unblock_events = false;
>> }
>> }
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index fdf25b8d6e78..577a693165d8 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 test_bit(BD_FLAG_MAKE_IT_FAIL, &part->flags) &&
>> + 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 (!test_bit(BD_FLAG_HAS_SUBMIT_BIO, &bio->bi_bdev->flags)) {
>> 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 (!test_bit(BD_FLAG_HAS_SUBMIT_BIO, &bio->bi_bdev->flags))
>> __submit_bio_noacct_mq(bio);
>> else
>> __submit_bio_noacct(bio);
>> diff --git a/block/genhd.c b/block/genhd.c
>> index c9d06f72c587..026f4c6d5b7e 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)
>> + set_bit(BD_FLAG_HAS_SUBMIT_BIO, &disk->part0->flags);
>>
>> /*
>> * 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",
>> + test_bit(BD_FLAG_MAKE_IT_FAIL, &dev_to_bdev(dev)->flags));
>> }
>>
>> ssize_t part_fail_store(struct device *dev,
>> @@ -1072,7 +1074,7 @@ 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;
>> + set_bit(BD_FLAG_MAKE_IT_FAIL, &dev_to_bdev(dev)->flags);
>>
>> return count;
>> }
>> diff --git a/block/ioctl.c b/block/ioctl.c
>> index 4160f4e6bd5b..a548c718a5fb 100644
>> --- a/block/ioctl.c
>> +++ b/block/ioctl.c
>> @@ -394,7 +394,7 @@ static int blkdev_roset(struct block_device *bdev, unsigned cmd,
>> if (ret)
>> return ret;
>> }
>> - bdev->bd_read_only = n;
>> + set_bit(BD_FLAG_READ_ONLY, &bdev->flags);
>> return 0;
>> }
>>
>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>> index 52e264d5a830..95bd26c62655 100644
>> --- a/include/linux/blk_types.h
>> +++ b/include/linux/blk_types.h
>> @@ -37,17 +37,20 @@ 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;
>> struct gendisk * bd_disk;
>> struct request_queue * bd_queue;
>> struct disk_stats __percpu *bd_stats;
>> + unsigned long flags;
>> unsigned long bd_stamp;
>> - bool bd_read_only; /* read-only policy */
>> u8 bd_partno;
>> - bool bd_write_holder;
>> - bool bd_has_submit_bio;
>
> The idea looks good, but not necessary to add new 8 bytes, and you may
> put all these flags and `bd_partno` into single 'unsigned long', and add
> helpers to retrieve part no, since there are not many ->bd_partno
> references.
Hi, I'm not quite sure which is the best way to implement this, anyway,
I come up with following implementation, can you please take a look
before I send a new version?
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 52e264d5a830..4e29774b14fd 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -37,6 +37,12 @@ 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
+#define BD_FLAGS_MAX 16
+
struct block_device {
sector_t bd_start_sect;
sector_t bd_nr_sectors;
@@ -44,10 +50,20 @@ 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 */
- u8 bd_partno;
- bool bd_write_holder;
- bool bd_has_submit_bio;
+
+ /*
+ * In order to keep both flags and bd_partno in the first cacheline,
+ * first 16 bits are used for flags.
+ */
+ union {
+ unsigned long flags;
+ struct {
+#ifdef __LITTLE_ENDIAN
+ u16 __flags;
+#endif
+ u8 bd_partno;
+ };
+ };
Thanks,
Kuai
>
> Thanks,
> Ming
>
>
> .
>
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