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: Christoph Hellwig <hch@lst.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -15,7 +15,6 @@
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#include "writeback.h"
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h>
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#include <linux/debugfs.h>
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#include <linux/genhd.h>
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#include <linux/idr.h>
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@ -64,13 +63,14 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
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{
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const char *err;
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struct cache_sb_disk *s;
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struct buffer_head *bh = __bread(bdev, 1, SB_SIZE);
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struct page *page;
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unsigned int i;
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if (!bh)
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page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
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SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
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if (IS_ERR(page))
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return "IO error";
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s = (struct cache_sb_disk *)bh->b_data;
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s = page_address(page) + offset_in_page(SB_OFFSET);
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sb->offset = le64_to_cpu(s->offset);
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sb->version = le64_to_cpu(s->version);
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@ -188,12 +188,10 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
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}
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sb->last_mount = (u32)ktime_get_real_seconds();
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err = NULL;
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get_page(bh->b_page);
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*res = s;
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return NULL;
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err:
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put_bh(bh);
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put_page(page);
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return err;
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}
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@ -148,6 +148,7 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys)
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#define BCACHE_SB_MAX_VERSION 4
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#define SB_SECTOR 8
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#define SB_OFFSET (SB_SECTOR << SECTOR_SHIFT)
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#define SB_SIZE 4096
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#define SB_LABEL_SIZE 32
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#define SB_JOURNAL_BUCKETS 256U
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