All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christoph Hellwig <hch@lst.de>
To: colyli@suse.de
Cc: kent.overstreet@gmail.com, liangchen.linux@gmail.com,
	linux-bcache@vger.kernel.org, linux-block@vger.kernel.org
Subject: [PATCH 7/7] bcache: use read_cache_page_gfp to read the superblock
Date: Mon,  9 Dec 2019 10:38:29 +0100	[thread overview]
Message-ID: <20191209093829.19703-8-hch@lst.de> (raw)
In-Reply-To: <20191209093829.19703-1-hch@lst.de>

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>
---
 drivers/md/bcache/super.c   | 16 +++++++---------
 include/uapi/linux/bcache.h |  1 +
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index df41d103fa34..ecb24316381f 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -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;
 }
 
diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
index 1d8b3a9fc080..9a1965c6c3d0 100644
--- a/include/uapi/linux/bcache.h
+++ b/include/uapi/linux/bcache.h
@@ -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
-- 
2.20.1


  parent reply	other threads:[~2019-12-09  9:38 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-09  9:38 bcache kbuild cleanups Christoph Hellwig
2019-12-09  9:38 ` [PATCH 1/7] bcache: cached_dev_free needs to put the sb page Christoph Hellwig
2019-12-09  9:38 ` [PATCH 2/7] bcache: use a separate data structure for the on-disk super block Christoph Hellwig
2019-12-09  9:38 ` [PATCH 3/7] bcache: rework error unwinding in register_bcache Christoph Hellwig
2019-12-09  9:38 ` [PATCH 4/7] bcache: transfer the sb_page reference to register_{bdev,cache} Christoph Hellwig
2019-12-09  9:38 ` [PATCH 5/7] bcache: return a pointer to the on-disk sb from read_super Christoph Hellwig
2019-12-09  9:38 ` [PATCH 6/7] bcache: store a pointer to the on-disk sb in the cache and cached_dev structures Christoph Hellwig
2019-12-09  9:38 ` Christoph Hellwig [this message]
2019-12-09  9:59 ` bcache kbuild cleanups Coly Li
2019-12-11 15:17   ` Liang C
2019-12-12 15:34     ` Christoph Hellwig
2019-12-12 15:35 bcache superblock reading / writing v2 Christoph Hellwig
2019-12-12 15:36 ` [PATCH 7/7] bcache: use read_cache_page_gfp to read the superblock Christoph Hellwig

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191209093829.19703-8-hch@lst.de \
    --to=hch@lst.de \
    --cc=colyli@suse.de \
    --cc=kent.overstreet@gmail.com \
    --cc=liangchen.linux@gmail.com \
    --cc=linux-bcache@vger.kernel.org \
    --cc=linux-block@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.