linux-ext4 - [PATCH] ext4: correct the number of blocks that has been deallocated in ext4_free_hole

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Date:	Mon, 28 Jan 2013 11:44:27 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	Zheng Liu <wenqing.lz@...bao.com>, "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH] ext4: correct the number of blocks that has been deallocated in ext4_free_hole_blocks

From: Zheng Liu <wenqing.lz@...bao.com>

This commit fixes a bug in ext4_free_hole_blocks that iff the number of
hole blocks is equal to EXT4_NDIR_BLOCKS and the first block of the hole
is a direct block, the number of deallocated blocks is wrong.

This bug can be triggered by the following commands:

  dd if=/dev/zero of=/mnt/testfile bs=4k count=16
  xfs_io -c "fpunch 4k 48k" -c "fiemap -v" /mnt/testfile

[wrong result]
 EXT: FILE-OFFSET      BLOCK-RANGE      TOTAL FLAGS
   0: [0..7]:          274560..274567       8 0x1000
   1: [8..95]:         hole                88
   2: [96..127]:       274656..274687      32 0x1001

[expected result]
 EXT: FILE-OFFSET      BLOCK-RANGE      TOTAL FLAGS
   0: [0..7]:          278528..278535       8 0x1000
   1: [8..103]:        hole                96
   2: [104..127]:      278632..278655      24 0x1001

Moreover this commit calls ext4_es_remove_extents() to remove some
delayed extents from extent status tree because now extent status tree
has been applied in the lastest kernel.  Meanwhile we never disable
dioread_nolock in ext4_ind_punch_hole() because this feature couldn't be
enabled for a indirect-based file, and we don't flush any unwritten io
because for a indirect-based file it needn't convert unwritten extents.

Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
Cc: "Theodore Ts'o" <tytso@....edu>
---
[This patch bases against dev branch]

 fs/ext4/indirect.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 3a33ca2..96a5c1f 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1582,7 +1582,7 @@ static int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,
 					       level, first, count, num);
 			if (ret)
 				goto err;
-			if (count > max)
+			if (count > max - first)
 				count -= max - first;
 			else
 				break;
@@ -1661,15 +1661,11 @@ int ext4_ind_punch_hole(struct file *file, loff_t offset, loff_t length)
 	}
 
 	/* Wait all existing dio works, newcomers will block on i_mutex */
-	ext4_inode_block_unlocked_dio(inode);
-	err = ext4_flush_unwritten_io(inode);
-	if (err)
-		goto out_dio;
 	inode_dio_wait(inode);
 
 	handle = start_transaction(inode);
 	if (IS_ERR(handle))
-		goto out_dio;
+		goto out_mutex;
 
 	/*
 	 * Now we need to zero out the non-page-aligned data in the
@@ -1738,6 +1734,8 @@ int ext4_ind_punch_hole(struct file *file, loff_t offset, loff_t length)
 	down_write(&EXT4_I(inode)->i_data_sem);
 	ext4_discard_preallocations(inode);
 
+	err = ext4_es_remove_extent(inode, first_block,
+				    stop_block - first_block);
 	err = ext4_free_hole_blocks(handle, inode, first_block, stop_block);
 
 	ext4_discard_preallocations(inode);
@@ -1752,8 +1750,6 @@ out:
 	ext4_mark_inode_dirty(handle, inode);
 	ext4_journal_stop(handle);
 
-out_dio:
-	ext4_inode_resume_unlocked_dio(inode);
 out_mutex:
 	mutex_unlock(&inode->i_mutex);
 
-- 
1.7.12.rc2.18.g61b472e

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