Commit 6321bef0 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

bcache: use read_cache_page_gfp to read the superblock 



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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 475389ae

drivers/md/bcache/super.c

+7 −9
Original line number Diff line number Diff line
@@ -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;

}

include/uapi/linux/bcache.h

+1 −0
Original line number Diff line number Diff line
@@ -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

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