From: Aneesh Kumar K.V Date: Wed, 13 May 2009 22:36:58 +0000 (-0400) Subject: ext4: Fix sub-block zeroing for writes into preallocated extents Patch-mainline: 2.6.30 Git-commit: 9c1ee184a30394e54165fa4c15923cabd952c106 References: bnc#503161 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 Signed-off-by: "Theodore Ts'o" Acked-by: Jeff Mahoney --- fs/ext4/extents.c | 2 ++ fs/ext4/inode.c | 7 +++++++ 2 files changed, 9 insertions(+) --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -2664,6 +2664,8 @@ int ext4_ext_get_blocks(handle_t *handle 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; } --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2220,6 +2220,13 @@ static int ext4_da_get_block_prep(struct 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; }