Hi Changwei,
>>>
> Before ocfs2 supporting allocating clusters while doing append-dio, all append
> dio will fall back to buffer io to allocate clusters firstly. Also, when it
> steps on a file hole, it will fall back to buffer io, too. But for current
> code, writing to file hole will leverage dio to allocate clusters. This is
> not
> right, since whether append-io is enabled tells the capability whether ocfs2
> can
> allocate space while doing dio.
> So introduce file hole check function back into ocfs2.
> Once ocfs2 is doing dio upon a file hole with append-dio disabled, it will
> fall
> back to buffer IO to allocate clusters.
>
> Signed-off-by: Changwei Ge <ge.chang...@h3c.com>
> ---
> fs/ocfs2/aops.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index d151632..a982cf6 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -2414,6 +2414,44 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
> return ret;
> }
>
> +/*
> + * Will look for holes and unwritten extents in the range starting at
> + * pos for count bytes (inclusive).
> + */
Why do we also need to look for unwritten extents here? unwritten extents
means, the clusters have been allocated, but have not been written yet.
Unwritten extents will not bring any block allocation, my understanding is
right here?
> +static int ocfs2_check_range_for_holes(struct inode *inode, loff_t pos,
> + size_t count)
> +{
> + int ret = 0;
> + unsigned int extent_flags;
> + u32 cpos, clusters, extent_len, phys_cpos;
> + struct super_block *sb = inode->i_sb;
> +
> + cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
> + clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
Please consider data-inline case, if in data-inline case, we maybe need not to
allocate more cluster.
Then, if there is not any more block need to be allocated, we should make the
check return true.
> +
> + while (clusters) {
> + ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
> + &extent_flags);
> + if (ret < 0) {
> + mlog_errno(ret);
> + goto out;
> + }
> +
> + if (phys_cpos == 0 || (extent_flags & OCFS2_EXT_UNWRITTEN)) {
> + ret = 1;
> + break;
> + }
> +
> + if (extent_len > clusters)
> + extent_len = clusters;
> +
> + clusters -= extent_len;
> + cpos += extent_len;
> + }
> +out:
> + return ret;
> +}
> +
> static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
> {
> struct file *file = iocb->ki_filp;
> @@ -2429,8 +2467,10 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb,
> struct iov_iter *iter)
> return 0;
>
> /* Fallback to buffered I/O if we do not support append dio. */
> - if (iocb->ki_pos + iter->count > i_size_read(inode) &&
> - !ocfs2_supports_append_dio(osb))
> + if (!ocfs2_supports_append_dio(osb) &&
> + (iocb->ki_pos + iter->count > i_size_read(inode) ||
> + ocfs2_check_range_for_holes(inode, iocb->ki_pos,
> + iter->count)))
> return 0;
>
> if (iov_iter_rw(iter) == READ)
> --
> 2.7.4
>
> _______________________________________________
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