Re: [PATCH] ext4: Fix ext4_bmap to flush the data to the disk with delalloc

Aneesh Kumar K.V
2008-06-18T18:31:07Z

On Wed, Jun 18, 2008 at 01:03:32PM -0500, Eric Sandeen wrote:
> Aneesh Kumar K.V wrote:
> > With delalloc we don't do block allocation in the write_begin/write_end.
> > So when using bmap we first need to flush data to the disk so that blocks
> > get allocated and then call generic_block_bmap.
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > ---
> > fs/ext4/inode.c | 11 +++++++++++
> > 1 files changed, 11 insertions(+), 0 deletions(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 7035621..cfeb869 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -1833,6 +1833,17 @@ sector_t ext4_bmap(struct address_space *mapping, sector_t block)
> > journal_t *journal;
> > int err;
> >
> > + if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
> > + test_opt(inode->i_sb, DELALLOC)) {
> > + /*
> > + * With delalloc we want to sync the file
> > + * so that we can make sure we allocate
> > + * blocks for file
> > + */
> > + filemap_fdatawrite(mapping);
> > + filemap_fdatawait(mapping);
> > + }
>
> This seems fine.
>
> I wonder, does it make any sense at all to only do the flushing if the
> block we wish to map is actually in a delalloc state at the moment?
>

I am not sure it is worth the complexity considering bmap is not a
frequently used API. Initially I was even thinking should i be doing
it only for delalloc. That test seems to be a simple one to put.

-aneesh