linux-ext4 - [PATCH -V5] ext4: Use -1 as the fake block number for delayed new buffer

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Message-ID: <20090512151754.GC23862@skywalker>
Date:	Tue, 12 May 2009 20:47:54 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	cmm@...ibm.com, tytso@....edu, sandeen@...hat.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH -V5] ext4: Use -1 as the fake block number for delayed new
	buffer_head


ext4: Use a fake block number for delayed new buffer_head

From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

Use a very large unsigned number (~0xffff) as as the fake block number
for the delayed new buffer. The VFS should never try to write out this
number, but if it does, this will make it obvious.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
 fs/ext4/inode.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 498cf8b..4b1478c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2297,6 +2297,10 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 				  struct buffer_head *bh_result, int create)
 {
 	int ret = 0;
+	sector_t invalid_block = ~((sector_t) 0xffff);
+
+	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
+		invalid_block = ~0;
 
 	BUG_ON(create == 0);
 	BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
@@ -2318,7 +2322,7 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 			/* not enough space to reserve */
 			return ret;
 
-		map_bh(bh_result, inode->i_sb, 0);
+		map_bh(bh_result, inode->i_sb, invalid_block);
 		set_buffer_new(bh_result);
 		set_buffer_delay(bh_result);
 	} else if (ret > 0) {
--
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