btrfs: Extract duplicate decompress code
Add a common function to copy decompressed data from working buffer
to bio pages.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 8faa2df..f745287 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -904,3 +904,95 @@
{
free_workspaces();
}
+
+/*
+ * Copy uncompressed data from working buffer to pages.
+ *
+ * buf_start is the byte offset we're of the start of our workspace buffer.
+ *
+ * total_out is the last byte of the buffer
+ */
+int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
+ unsigned long total_out, u64 disk_start,
+ struct bio_vec *bvec, int vcnt,
+ unsigned long *page_index,
+ unsigned long *pg_offset)
+{
+ unsigned long buf_offset;
+ unsigned long current_buf_start;
+ unsigned long start_byte;
+ unsigned long working_bytes = total_out - buf_start;
+ unsigned long bytes;
+ char *kaddr;
+ struct page *page_out = bvec[*page_index].bv_page;
+
+ /*
+ * 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(page_out) - 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(PAGE_CACHE_SIZE - *pg_offset,
+ PAGE_CACHE_SIZE - buf_offset);
+ bytes = min(bytes, working_bytes);
+ kaddr = kmap_atomic(page_out, KM_USER0);
+ memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
+ kunmap_atomic(kaddr, KM_USER0);
+ flush_dcache_page(page_out);
+
+ *pg_offset += bytes;
+ buf_offset += bytes;
+ working_bytes -= bytes;
+ current_buf_start += bytes;
+
+ /* check if we need to pick another page */
+ if (*pg_offset == PAGE_CACHE_SIZE) {
+ (*page_index)++;
+ if (*page_index >= vcnt)
+ return 0;
+
+ page_out = bvec[*page_index].bv_page;
+ *pg_offset = 0;
+ start_byte = page_offset(page_out) - disk_start;
+
+ /*
+ * make sure our new page is covered by this
+ * working buffer
+ */
+ if (total_out <= start_byte)
+ return 1;
+
+ /*
+ * 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;
+ }
+ }
+ }
+
+ return 1;
+}