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ext4: Fix sub-block zeroing for writes into preallocated extents 

We need to mark the buffer_head mapping preallocated space as new
during write_begin. Otherwise we don't zero out the page cache content
properly for a partial write. This will cause file corruption with
preallocation.

Now that we mark the buffer_head new we also need to have a valid
buffer_head blocknr so that unmap_underlying_metadata() unmaps the
correct block.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Aneesh Kumar K.V 2009-05-13 18:36:58 -04:00 committed by Theodore Ts'o
parent 091bf7624d
commit 9c1ee184a3
2 changed files with 9 additions and 0 deletions
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2
fs/ext4/extents.c
View File

@ -2875,6 +2875,8 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
if (allocated > max_blocks)
allocated = max_blocks;
set_buffer_unwritten(bh_result);
bh_result->b_bdev = inode->i_sb->s_bdev;
bh_result->b_blocknr = newblock;
goto out2;
}

7
fs/ext4/inode.c
View File

@ -2323,6 +2323,13 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
set_buffer_delay(bh_result);
} else if (ret > 0) {
bh_result->b_size = (ret << inode->i_blkbits);
/*
* With sub-block writes into unwritten extents
* we also need to mark the buffer as new so that
* the unwritten parts of the buffer gets correctly zeroed.
*/
if (buffer_unwritten(bh_result))
set_buffer_new(bh_result);
ret = 0;
}