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authorQu Wenruo <wqu@suse.com>2021-07-05 05:00:58 +0300
committerDavid Sterba <dsterba@suse.com>2021-08-23 14:19:04 +0300
commit1c3dc1731ed2b3757b25533c5245926ffc94f7dc (patch)
tree7b025f2c58c884a06fc6165813d009e21f2ed036 /fs/btrfs/compression.h
parent557023ea9f06baf2659b232b08b8e8711f7001a6 (diff)
downloadlinux-1c3dc1731ed2b3757b25533c5245926ffc94f7dc.tar.xz
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/compression.h')
-rw-r--r--fs/btrfs/compression.h5
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index c359f20920d0..399be0b435bf 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -86,9 +86,8 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
unsigned long *total_out);
int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
unsigned long start_byte, size_t srclen, size_t destlen);
-int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
- unsigned long total_out, u64 disk_start,
- struct bio *bio);
+int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
+ struct compressed_bio *cb, u32 decompressed);
blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
unsigned int len, u64 disk_start,