}
/*
- * Copy uncompressed data from working buffer to pages.
+ * Copy decompressed data from working buffer to pages.
*
- * buf_start is the byte offset we're of the start of our workspace buffer.
+ * @buf: The decompressed data buffer
+ * @buf_len: The decompressed data length
+ * @decompressed: Number of bytes that are already decompressed inside the
+ * compressed extent
+ * @cb: The compressed extent descriptor
+ * @orig_bio: The original bio that the caller wants to read for
*
- * total_out is the last byte of the buffer
+ * An easier to understand graph is like below:
+ *
+ * |<- orig_bio ->| |<- orig_bio->|
+ * |<------- full decompressed extent ----->|
+ * |<----------- @cb range ---->|
+ * | |<-- @buf_len -->|
+ * |<--- @decompressed --->|
+ *
+ * Note that, @cb can be a subpage of the full decompressed extent, but
+ * @cb->start always has the same as the orig_file_offset value of the full
+ * decompressed extent.
+ *
+ * When reading compressed extent, we have to read the full compressed extent,
+ * while @orig_bio may only want part of the range.
+ * Thus this function will ensure only data covered by @orig_bio will be copied
+ * to.
+ *
+ * Return 0 if we have copied all needed contents for @orig_bio.
+ * Return >0 if we need continue decompress.
*/
-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)
{
- unsigned long buf_offset;
- unsigned long current_buf_start;
- unsigned long start_byte;
- unsigned long prev_start_byte;
- unsigned long working_bytes = total_out - buf_start;
- unsigned long bytes;
- struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
-
- /*
- * start byte is the first byte of the page we're currently
- * copying into relative to the start of the compressed data.
- */
- start_byte = page_offset(bvec.bv_page) - disk_start;
-
- /* we haven't yet hit data corresponding to this page */
- if (total_out <= start_byte)
- return 1;
-
- /*
- * the start of the data we care about is offset into
- * the middle of our working buffer
- */
- if (total_out > start_byte && buf_start < start_byte) {
- buf_offset = start_byte - buf_start;
- working_bytes -= buf_offset;
- } else {
- buf_offset = 0;
- }
- current_buf_start = buf_start;
-
- /* copy bytes from the working buffer into the pages */
- while (working_bytes > 0) {
- bytes = min_t(unsigned long, bvec.bv_len,
- PAGE_SIZE - (buf_offset % PAGE_SIZE));
- bytes = min(bytes, working_bytes);
+ struct bio *orig_bio = cb->orig_bio;
+ /* Offset inside the full decompressed extent */
+ u32 cur_offset;
+
+ cur_offset = decompressed;
+ /* The main loop to do the copy */
+ while (cur_offset < decompressed + buf_len) {
+ struct bio_vec bvec;
+ size_t copy_len;
+ u32 copy_start;
+ /* Offset inside the full decompressed extent */
+ u32 bvec_offset;
+
+ bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
+ /*
+ * cb->start may underflow, but subtracting that value can still
+ * give us correct offset inside the full decompressed extent.
+ */
+ bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start;
- memcpy_to_page(bvec.bv_page, bvec.bv_offset, buf + buf_offset,
- bytes);
- flush_dcache_page(bvec.bv_page);
+ /* Haven't reached the bvec range, exit */
+ if (decompressed + buf_len <= bvec_offset)
+ return 1;
- buf_offset += bytes;
- working_bytes -= bytes;
- current_buf_start += bytes;
-
- /* check if we need to pick another page */
- bio_advance(bio, bytes);
- if (!bio->bi_iter.bi_size)
- return 0;
- bvec = bio_iter_iovec(bio, bio->bi_iter);
- prev_start_byte = start_byte;
- start_byte = page_offset(bvec.bv_page) - disk_start;
+ copy_start = max(cur_offset, bvec_offset);
+ copy_len = min(bvec_offset + bvec.bv_len,
+ decompressed + buf_len) - copy_start;
+ ASSERT(copy_len);
/*
- * We need to make sure we're only adjusting
- * our offset into compression working buffer when
- * we're switching pages. Otherwise we can incorrectly
- * keep copying when we were actually done.
+ * Extra range check to ensure we didn't go beyond
+ * @buf + @buf_len.
*/
- if (start_byte != prev_start_byte) {
- /*
- * make sure our new page is covered by this
- * working buffer
- */
- if (total_out <= start_byte)
- return 1;
+ ASSERT(copy_start - decompressed < buf_len);
+ memcpy_to_page(bvec.bv_page, bvec.bv_offset,
+ buf + copy_start - decompressed, copy_len);
+ flush_dcache_page(bvec.bv_page);
+ cur_offset += copy_len;
- /*
- * the next page in the biovec might not be adjacent
- * to the last page, but it might still be found
- * inside this working buffer. bump our offset pointer
- */
- if (total_out > start_byte &&
- current_buf_start < start_byte) {
- buf_offset = start_byte - buf_start;
- working_bytes = total_out - start_byte;
- current_buf_start = buf_start + buf_offset;
- }
- }
+ bio_advance(orig_bio, copy_len);
+ /* Finished the bio */
+ if (!orig_bio->bi_iter.bi_size)
+ return 0;
}
-
return 1;
}
unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
unsigned long buf_start;
struct page **pages_in = cb->compressed_pages;
- u64 disk_start = cb->start;
- struct bio *orig_bio = cb->orig_bio;
data_in = page_address(pages_in[page_in_index]);
workspace->strm.next_in = data_in;
if (buf_start == total_out)
break;
- ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
- total_out, disk_start,
- orig_bio);
+ ret2 = btrfs_decompress_buf2page(workspace->buf,
+ total_out - buf_start, cb, buf_start);
if (ret2 == 0) {
ret = 0;
goto done;
data_in = page_address(pages_in[page_in_index]);
workspace->strm.next_in = data_in;
tmp = srclen - workspace->strm.total_in;
- workspace->strm.avail_in = min(tmp,
- PAGE_SIZE);
+ workspace->strm.avail_in = min(tmp, PAGE_SIZE);
}
}
if (ret != Z_STREAM_END)
done:
zlib_inflateEnd(&workspace->strm);
if (!ret)
- zero_fill_bio(orig_bio);
+ zero_fill_bio(cb->orig_bio);
return ret;
}
projects / kernel.git / commitdiff