On Tue, Jan 26, 2021 at 11:25:07AM +0900, Naohiro Aota wrote:
> If more than one IO is issued for one file extent, these IO can be written
> to separate regions on a device. Since we cannot map one file extent to
> such a separate area, we need to follow the "one IO == one ordered extent"
> rule.
>
> The Normal buffered, uncompressed, not pre-allocated write path (used by
> cow_file_range()) sometimes does not follow this rule. It can write a part
> of an ordered extent when specified a region to write e.g., when its
> called from fdatasync().
>
> Introduces a dedicated (uncompressed buffered) data write path for ZONED
> mode. This write path will CoW the region and write it at once.
>
> Reviewed-by: Josef Bacik <[email protected]>
> Signed-off-by: Naohiro Aota <[email protected]>
> ---
> fs/btrfs/inode.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index a9bf78eaed42..6d43aaa1f537 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -1400,6 +1400,29 @@ static int cow_file_range_async(struct btrfs_inode
> *inode,
> return 0;
> }
>
> +static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
> + struct page *locked_page, u64 start,
> + u64 end, int *page_started,
> + unsigned long *nr_written)
> +{
> + int ret;
> +
> + ret = cow_file_range(inode, locked_page, start, end,
> + page_started, nr_written, 0);
> + if (ret)
> + return ret;
> +
> + if (*page_started)
> + return 0;
> +
> + __set_page_dirty_nobuffers(locked_page);
> + account_page_redirty(locked_page);
> + extent_write_locked_range(&inode->vfs_inode, start, end, WB_SYNC_ALL);
> + *page_started = 1;
> +
> + return 0;
> +}
> +
> static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
> u64 bytenr, u64 num_bytes)
> {
> @@ -1879,17 +1902,24 @@ int btrfs_run_delalloc_range(struct btrfs_inode
> *inode, struct page *locked_page
> {
> int ret;
> int force_cow = need_force_cow(inode, start, end);
> + const bool do_compress = inode_can_compress(inode) &&
> + inode_need_compress(inode, start, end);
This would make sense to cache the values, but inode_need_compress is
quite heavy as it runs the compression heuristic. This would affect all
cases and drop some perf.
> + const bool zoned = btrfs_is_zoned(inode->root->fs_info);
>
> if (inode->flags & BTRFS_INODE_NODATACOW && !force_cow) {
> + ASSERT(!zoned);
> ret = run_delalloc_nocow(inode, locked_page, start, end,
> page_started, 1, nr_written);
> } else if (inode->flags & BTRFS_INODE_PREALLOC && !force_cow) {
> + ASSERT(!zoned);
> ret = run_delalloc_nocow(inode, locked_page, start, end,
> page_started, 0, nr_written);
> - } else if (!inode_can_compress(inode) ||
> - !inode_need_compress(inode, start, end)) {
> + } else if (!do_compress && !zoned) {
> ret = cow_file_range(inode, locked_page, start, end,
> page_started, nr_written, 1);
> + } else if (!do_compress && zoned) {
> + ret = run_delalloc_zoned(inode, locked_page, start, end,
> + page_started, nr_written);
The part of the condition is shared so it should be structured lik
} else if (!<the compression checks>) {
if (zoned)
run_delalloc_zoned
else
cow_file_range
} ...
> } else {
> set_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, &inode->runtime_flags);
> ret = cow_file_range_async(inode, wbc, locked_page, start, end,
> --
> 2.27.0
