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authorQu Wenruo <wqu@suse.com>2025-01-24 17:29:58 +1030
committerDavid Sterba <dsterba@suse.com>2025-03-18 20:35:41 +0100
commitaa60fe12b4f49f49fc73e5023f8675e2df1f7805 (patch)
tree25f2baf75ea08e27d600e4879a674243e8266c5a
parent87d6aaf79bbeedda4af4c104fa02ff57fda54b12 (diff)
btrfs: zlib: refactor S390x HW acceleration buffer preparation
Currently for s390x HW zlib compression, to get the best performance we need a buffer size which is larger than a page. This means we need to copy multiple pages into workspace->buf, then use that buffer as zlib compression input. Currently it's hardcoded using page sized folio, and all the handling are deep inside a loop. Refactor the code by: - Introduce a dedicated helper to do the buffer copy The new helper will be called copy_data_into_buffer(). - Add extra ASSERT()s * Make sure we only go into the function for hardware acceleration * Make sure we still get page sized folio - Prepare for future large folios This means we will rely on the folio size, other than PAGE_SIZE to do the copy. - Handle the folio mapping and unmapping inside the helper function For S390x hardware acceleration case, it never utilize the @data_in pointer, thus we can do folio mapping/unmapping all inside the function. Acked-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Tested-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
-rw-r--r--fs/btrfs/zlib.c84
1 files changed, 55 insertions, 29 deletions
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index c9e92c6941ec..96e3b1e09bf6 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -94,6 +94,47 @@ fail:
return ERR_PTR(-ENOMEM);
}
+/*
+ * Helper for S390x with hardware zlib compression support.
+ *
+ * That hardware acceleration requires a buffer size larger than a single page
+ * to get ideal performance, thus we need to do the memory copy rather than
+ * use the page cache directly as input buffer.
+ */
+static int copy_data_into_buffer(struct address_space *mapping,
+ struct workspace *workspace, u64 filepos,
+ unsigned long length)
+{
+ u64 cur = filepos;
+
+ /* It's only for hardware accelerated zlib code. */
+ ASSERT(zlib_deflate_dfltcc_enabled());
+
+ while (cur < filepos + length) {
+ struct folio *folio;
+ void *data_in;
+ unsigned int offset;
+ unsigned long copy_length;
+ int ret;
+
+ ret = btrfs_compress_filemap_get_folio(mapping, cur, &folio);
+ if (ret < 0)
+ return ret;
+ /* No large folio support yet. */
+ ASSERT(!folio_test_large(folio));
+
+ offset = offset_in_folio(folio, cur);
+ copy_length = min(folio_size(folio) - offset,
+ filepos + length - cur);
+
+ data_in = kmap_local_folio(folio, offset);
+ memcpy(workspace->buf + cur - filepos, data_in, copy_length);
+ kunmap_local(data_in);
+ cur += copy_length;
+ }
+ return 0;
+}
+
int zlib_compress_folios(struct list_head *ws, struct address_space *mapping,
u64 start, struct folio **folios, unsigned long *out_folios,
unsigned long *total_in, unsigned long *total_out)
@@ -105,8 +146,6 @@ int zlib_compress_folios(struct list_head *ws, struct address_space *mapping,
int nr_folios = 0;
struct folio *in_folio = NULL;
struct folio *out_folio = NULL;
- unsigned long bytes_left;
- unsigned int in_buf_folios;
unsigned long len = *total_out;
unsigned long nr_dest_folios = *out_folios;
const unsigned long max_out = nr_dest_folios * PAGE_SIZE;
@@ -150,34 +189,21 @@ int zlib_compress_folios(struct list_head *ws, struct address_space *mapping,
* the workspace buffer if required.
*/
if (workspace->strm.avail_in == 0) {
- bytes_left = len - workspace->strm.total_in;
- in_buf_folios = min(DIV_ROUND_UP(bytes_left, PAGE_SIZE),
- workspace->buf_size / PAGE_SIZE);
- if (in_buf_folios > 1) {
- int i;
-
- /* S390 hardware acceleration path, not subpage. */
- ASSERT(!btrfs_is_subpage(
- inode_to_fs_info(mapping->host),
- mapping));
- for (i = 0; i < in_buf_folios; i++) {
- if (data_in) {
- kunmap_local(data_in);
- folio_put(in_folio);
- data_in = NULL;
- }
- ret = btrfs_compress_filemap_get_folio(mapping,
- start, &in_folio);
- if (ret < 0)
- goto out;
- data_in = kmap_local_folio(in_folio, 0);
- copy_page(workspace->buf + i * PAGE_SIZE,
- data_in);
- start += PAGE_SIZE;
- }
+ unsigned long bytes_left = len - workspace->strm.total_in;
+ unsigned int copy_length = min(bytes_left, workspace->buf_size);
+
+ /*
+ * This can only happen when hardware zlib compression is
+ * enabled.
+ */
+ if (copy_length > PAGE_SIZE) {
+ ret = copy_data_into_buffer(mapping, workspace,
+ start, copy_length);
+ if (ret < 0)
+ goto out;
+ start += copy_length;
workspace->strm.next_in = workspace->buf;
- workspace->strm.avail_in = min(bytes_left,
- in_buf_folios << PAGE_SHIFT);
+ workspace->strm.avail_in = copy_length;
} else {
unsigned int pg_off;
unsigned int cur_len;