Hi Changwei,
On 2017/12/26 15:03, Changwei Ge wrote:
> The intention of this patch is to provide an option to ocfs2 users whether
> to allocate disk space while doing dio write.
>
> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
> toggling append-dio feature. It rather makes ocfs2 configurable and
> flexible.
>
It is too strange to make ocfs2 fall back to buffer io by toggling append-dio
feature.
> So if something bad happens to dio write with space allocation, we can
> still make ocfs2 fall back to buffer io. It's an option not a mandatory
> action.:)
Now the ocfs2 supports fill holes during direct io whether or not supporting
append-dio feature
and we can directly fix the problem.
I think it is meaningless to provide an temporary option to turn off it.
>
> Besides, append-dio feature is key to whether to allocate space with dio
> writing. So writing to file hole and enlarging file(appending file) should
> have the same reflection to append-dio feature.
>
> Signed-off-by: Changwei Ge <ge.chang...@h3c.com>
> ---
> fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 50 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index d151632..32e60c0 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -2414,12 +2414,52 @@ 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).
> + * Return value 1 indicates hole exists, 0 not exists, others indicate error.
> + */
> +static int ocfs2_range_has_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;
> +
> + 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) {
> + ret = 1;
> + goto out;
> + }
> +
> + 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;
> struct inode *inode = file->f_mapping->host;
> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> get_block_t *get_block;
> + int ret;
>
> /*
> * Fallback to buffered I/O if we see an inode without
> @@ -2429,9 +2469,16 @@ 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))
> - return 0;
> + if (!ocfs2_supports_append_dio(osb)) {
> + if (iocb->ki_pos + iter->count > i_size_read(inode))
> + return 0;
> +
> + ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
> + if (ret == 1)
> + return 0;
> + else if (ret < 0)
> + return ret;
> + }
>
> if (iov_iter_rw(iter) == READ)
> get_block = ocfs2_lock_get_block;
>
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