On Wed, Jun 13, 2012 at 08:15:31PM -0400, Ted Ts'o wrote:
> Hi Zheng,
>
> I finally got around to reviewing this patch and I had one comment
>
> > Ext4 must make sure the transaction to be commited to the disk when
> > user opens a file with O_(D)SYNC flag and do a fallocate(2) call.
> >
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index 74f23c2..00e32d9 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -4356,6 +4356,8 @@ retry:
> > ret = PTR_ERR(handle);
> > break;
> > }
> > + if (file->f_flags & O_SYNC)
> > + ext4_handle_sync(handle);
> > ret = ext4_map_blocks(handle, inode, &map, flags);
> > if (ret <= 0) {
> > #ifdef EXT4FS_DEBUG
>
> For a large fallocate(), it can require multiple calls to
> ext4_map_blocks(), and we should only sync after we've allocated the
> last segment. We should also not force a sync if there is an error
> allocating blocks. So it seems to me this patch would be better; what
> do you think?
Hi Ted,
Thank you for your review. I agree with you that the following patch is
better.
Regards,
Zheng
> commit b790d70be9515dfaba59b0be0aff373e6867826d
> Author: Zheng Liu <gnehzuil.liu@xxxxxxxxx>
> Date: Wed Jun 13 20:15:01 2012 -0400
>
> ext4: honor O_(D)SYNC semantic in ext4_fallocate()
>
> Ext4 must make sure the transaction to be commited to the disk when
> user opens a file with O_(D)SYNC flag and do a fallocate(2) call.
>
> This problem had been reported by Christoph Hellwig in this thread:
> http://www.spinics.net/lists/linux-btrfs/msg13621.html
>
> Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 91341ec..f1089cb 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4420,6 +4420,8 @@ retry:
> ext4_falloc_update_inode(inode, mode, new_size,
> (map.m_flags & EXT4_MAP_NEW));
> ext4_mark_inode_dirty(handle, inode);
> + if ((file->f_flags & O_SYNC) && ret >= max_blocks)
> + ext4_handle_sync(handle);
> ret2 = ext4_journal_stop(handle);
> if (ret2)
> break;
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