linux-kernel - [PATCH] vfs: calculate block-size correctly

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Message-ID: <20100908100710.GA26365@zhongling.bej.apac.novell.com>
Date:	Wed, 8 Sep 2010 18:07:10 +0800
From:	Cong Meng <mcpacino@...il.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>,
	Nick Piggin <npiggin@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] vfs: calculate block-size correctly

I sent this patch half mount ago, but no response at all. If anything is
wrong, please tell me. Thanks a lots. This is my first time to send patch
to linux kernel.

The invocation of __getblk(bdev, block, size) will cause kernel stall if
the @size parameter is not equal to the blockr-size of @bdev, which is saved
in bdev->bd_inode->i_blkbits.

submit_bh() has the similar problem.

This patch calculates the block-size using i_blkbits.
So that, for example, __getblk() can get a 4K buffer head while the
block-size of @bdev is 1K.

Signed-off-by: Cong Meng <mcpacino@...il.com>
---
 fs/buffer.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 3e7dca2..f7f9d33 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1051,10 +1051,7 @@ grow_buffers(struct block_device *bdev, sector_t block, int size)
 	pgoff_t index;
 	int sizebits;
 
-	sizebits = -1;
-	do {
-		sizebits++;
-	} while ((size << sizebits) < PAGE_SIZE);
+	sizebits = PAGE_CACHE_SHIFT - bdev->bd_inode->i_blkbits;
 
 	index = block >> sizebits;
 
@@ -2924,7 +2921,7 @@ int submit_bh(int rw, struct buffer_head * bh)
 	 */
 	bio = bio_alloc(GFP_NOIO, 1);
 
-	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
+	bio->bi_sector = bh->b_blocknr << (bh->b_bdev->bd_inode->i_blkbits - 9);
 	bio->bi_bdev = bh->b_bdev;
 	bio->bi_io_vec[0].bv_page = bh->b_page;
 	bio->bi_io_vec[0].bv_len = bh->b_size;
--
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