commit: 5b41395fcc0265fc9f193aef9df39ce49d64677c
From: Yongqiang Yang <[email protected]>
Date: Mon, 4 Apr 2011 15:40:24 -0400
Subject: [PATCH] ext4: fix credits computing for indirect mapped files

When writing a contiguous set of blocks, two indirect blocks could be
needed depending on how the blocks are aligned, so we need to increase
the number of credits needed by one.

[ Also fixed a another bug which could further underestimate the
  number of journal credits needed by 1; the code was using integer
  division instead of DIV_ROUND_UP() -- tytso]

Signed-off-by: Yongqiang Yang <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Cc: [email protected]
---
 fs/ext4/inode.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1a86282..7d11e02 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5398,13 +5398,12 @@ static int ext4_indirect_trans_blocks(struct inode 
*inode, int nrblocks,
        /* if nrblocks are contiguous */
        if (chunk) {
                /*
-                * With N contiguous data blocks, it need at most
-                * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) indirect blocks
-                * 2 dindirect blocks
-                * 1 tindirect block
+                * With N contiguous data blocks, we need at most
+                * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
+                * 2 dindirect blocks, and 1 tindirect block
                 */
-               indirects = nrblocks / EXT4_ADDR_PER_BLOCK(inode->i_sb);
-               return indirects + 3;
+               return DIV_ROUND_UP(nrblocks,
+                                   EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
        }
        /*
         * if nrblocks are not contiguous, worse case, each block touch

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