在 2008-11-06四的 14:51 -0500，Theodore Ts'o写道：
> This fixes a 2.6.27 regression which was introduced in commit a02908f1.
>
> We weren't passing the chunk parameter down to the two subections,
> ext4_indirect_trans_blocks() and ext4_ext_index_trans_blocks(), with
> the result that massively overestimate the amount of credits needed by
> ext4_da_writepages, especially in the non-extents case. This causes
> failures especially on /boot partitions, which tend to be small and
> non-extent using since GRUB doesn't handle extents.
>
> Thanks to Joseph Fannin for reporting this bug.
>
Thanks for fixing this up!
However, looking at the code path, I wasn't sure if we got the delalloc
credits right. In ext4_da_writepages()->mpage_da_writepages(), the
credits is calculated based on the assumption that mpage_da_writepages()
doing* one* single chunk of contigugous allocation? So only one single
extent credit is reserved (here you see the "chunk" flag passed from the
ext4_da_writepages)
__mpage_da_writepage() does do single chunk of block allocation at a
time, but mpage_da_writepages()->write_cache_pages() will loop the page
vectors and probably will calling writepage->__mpage_da_writepage->
mpage_da_map_blocks() multiple times? Am I missing anything?
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> fs/ext4/inode.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 8dbf695..5a130b5 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4580,9 +4580,10 @@ static int ext4_indirect_trans_blocks(struct inode *inode, int nrblocks,
> static int ext4_index_trans_blocks(struct inode *inode, int nrblocks, int chunk)
> {
> if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL))
> - return ext4_indirect_trans_blocks(inode, nrblocks, 0);
> - return ext4_ext_index_trans_blocks(inode, nrblocks, 0);
> + return ext4_indirect_trans_blocks(inode, nrblocks, chunk);
> + return ext4_ext_index_trans_blocks(inode, nrblocks, chunk);
> }
> +
> /*
> * Account for index blocks, block groups bitmaps and block group
> * descriptor blocks if modify datablocks and index blocks
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