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authorQu Wenruo <wqu@suse.com>2021-07-05 10:00:58 +0800
committerDavid Sterba <dsterba@suse.com>2021-08-23 13:19:04 +0200
commit1c3dc1731ed2b3757b25533c5245926ffc94f7dc (patch)
tree7b025f2c58c884a06fc6165813d009e21f2ed036 /fs/btrfs/zstd.c
parent557023ea9f06baf2659b232b08b8e8711f7001a6 (diff)
btrfs: rework btrfs_decompress_buf2page()
There are several bugs inside the function btrfs_decompress_buf2page() - @start_byte doesn't take bvec.bv_offset into consideration Thus it can't handle case where the target range is not page aligned. - Too many helper variables There are tons of helper variables, @buf_offset, @current_buf_start, @start_byte, @prev_start_byte, @working_bytes, @bytes. This hurts anyone who wants to read the function. - No obvious main cursor for the iteartion A new problem caused by previous problem. - Comments for parameter list makes no sense Like @buf_start is the offset to @buf, or offset inside the full decompressed extent? (Spoiler alert, the later case) And @total_out acts more like @buf_start + @size_of_buf. The worst is @disk_start. The real meaning of it is the file offset of the full decompressed extent. This patch will rework the whole function by: - Add a proper comment with ASCII art to explain the parameter list - Rework parameter list The old @buf_start is renamed to @decompressed, to show how many bytes are already decompressed inside the full decompressed extent. The old @total_out is replaced by @buf_len, which is the decompressed data size. For old @disk_start and @bio, just pass @compressed_bio in. - Use single main cursor The main cursor will be @cur_file_offset, to show what's the current file offset. Other helper variables will be declared inside the main loop, and only minimal amount of helper variables: * offset_inside_decompressed_buf: The only real helper * copy_start_file_offset: File offset we start memcpy * bvec_file_offset: File offset of current bvec Even with all these extensive comments, the final function is still smaller than the original function, which is definitely a win. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/zstd.c')
-rw-r--r--fs/btrfs/zstd.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 200ba08bfae6..56dce9f00988 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -540,8 +540,6 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
struct page **pages_in = cb->compressed_pages;
- u64 disk_start = cb->start;
- struct bio *orig_bio = cb->orig_bio;
size_t srclen = cb->compressed_len;
ZSTD_DStream *stream;
int ret = 0;
@@ -582,7 +580,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
workspace->out_buf.pos = 0;
ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
- buf_start, total_out, disk_start, orig_bio);
+ total_out - buf_start, cb, buf_start);
if (ret == 0)
break;
@@ -607,7 +605,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
}
}
ret = 0;
- zero_fill_bio(orig_bio);
+ zero_fill_bio(cb->orig_bio);
done:
return ret;
}