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bcache: use read_cache_page_gfp to read the superblock

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Avoid a pointless dependency on buffer heads in bcache by simply open
coding reading a single page.  Also add a SB_OFFSET define for the
byte offset of the superblock instead of using magic numbers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2020-01-24 01:01:34 +08:00 committed by Jens Axboe
parent 475389ae5c
commit 6321bef028
2 changed files with 8 additions and 9 deletions
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16
drivers/md/bcache/super.c
View file

@ -15,7 +15,6 @@
#include "writeback.h"
#include <linux/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/debugfs.h>
#include <linux/genhd.h>
#include <linux/idr.h>
@ -64,13 +63,14 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
{
const char *err;
struct cache_sb_disk *s;
struct buffer_head *bh = __bread(bdev, 1, SB_SIZE);
struct page *page;
unsigned int i;
if (!bh)
page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
if (IS_ERR(page))
return "IO error";
s = (struct cache_sb_disk *)bh->b_data;
s = page_address(page) + offset_in_page(SB_OFFSET);
sb->offset = le64_to_cpu(s->offset);
sb->version = le64_to_cpu(s->version);
@ -188,12 +188,10 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
}
sb->last_mount = (u32)ktime_get_real_seconds();
err = NULL;
get_page(bh->b_page);
*res = s;
return NULL;
err:
put_bh(bh);
put_page(page);
return err;
}

1
include/uapi/linux/bcache.h
View file

@ -148,6 +148,7 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys)
#define BCACHE_SB_MAX_VERSION 4
#define SB_SECTOR 8
#define SB_OFFSET (SB_SECTOR << SECTOR_SHIFT)
#define SB_SIZE 4096
#define SB_LABEL_SIZE 32
#define SB_JOURNAL_BUCKETS 256U