On Fri, Jul 14, 2017 at 03:00:46PM +0300, Timofey Titovets wrote:
> For now that code just return true
> Later more complex heuristic code will be added
>
> Changes v1 -> v2:
> - Heuristic call moved into inode_need_compress() function
>
> Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
> ---
> fs/btrfs/compression.c | 22 ++++++++++++++++++++++
> fs/btrfs/compression.h | 2 ++
> fs/btrfs/inode.c | 18 ++++++++++++------
> 3 files changed, 36 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 2c0b7b57fcd5..d0cf2024def7 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -1046,3 +1046,25 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
>
> return 1;
> }
> +
> +/*
> + * Heuristic skeleton
> + * For now just would be a naive and very optimistic 'return true'.
> + */
> +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
> +{
> + u64 index = start >> PAGE_SHIFT;
> + u64 end_index = end >> PAGE_SHIFT;
> + struct page *page;
> + int ret = 1;
> +
> + while (index <= end_index) {
> + page = find_get_page(inode->i_mapping, index);
> + kmap(page);
> + kunmap(page);
> + put_page(page);
> + index++;
> + }
> +
> + return ret;
> +}
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index 87f6d3332163..8508ba6b9aef 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -129,4 +129,6 @@ struct btrfs_compress_op {
> extern const struct btrfs_compress_op btrfs_zlib_compress;
> extern const struct btrfs_compress_op btrfs_lzo_compress;
>
> +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);
> +
> #endif
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 06dea7c89bbd..27922b29fa4e 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -392,20 +392,26 @@ static noinline int add_async_extent(struct async_cow *cow,
> return 0;
> }
>
> -static inline int inode_need_compress(struct inode *inode)
> +static inline int inode_need_compress(struct inode *inode, u64 start, u64 end)
> {
> + int ret = 0;
> struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>
> /* force compress */
> if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
> - return 1;
> + goto try_compress;
> /* bad compression ratios */
> if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
> - return 0;
> + goto skip_compress;
> if (btrfs_test_opt(fs_info, COMPRESS) ||
> BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS ||
> BTRFS_I(inode)->force_compress)
> - return 1;
> + goto try_compress;
> + goto skip_compress;
> +try_compress:
> + ret = btrfs_compress_heuristic(inode, start, end);
> + return ret;
> +skip_compress:
> return 0;
That's a bit wilde goto skip_compress can be simple return 0. Also you
can drop ret and return btrfs_compress_heuristic(...);
Otherwise it looks ok, just the documentation side could be improved,
like describe the purpose and expected furure enhancements.
> }
>
> @@ -503,7 +509,7 @@ static noinline void compress_file_range(struct inode *inode,
> * inode has not been flagged as nocompress. This flag can
> * change at any time if we discover bad compression ratios.
> */
> - if (inode_need_compress(inode)) {
> + if (inode_need_compress(inode, start, end)) {
> WARN_ON(pages);
> pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
> if (!pages) {
> @@ -1576,7 +1582,7 @@ static int run_delalloc_range(void *private_data, struct page *locked_page,
> } else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) {
> ret = run_delalloc_nocow(inode, locked_page, start, end,
> page_started, 0, nr_written);
> - } else if (!inode_need_compress(inode)) {
> + } else if (!inode_need_compress(inode, start, end)) {
> ret = cow_file_range(inode, locked_page, start, end, end,
> page_started, nr_written, 1, NULL);
> } else {
> --
> 2.13.2
>
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