btrfs: prepare zlib to support bs > ps cases

This involves converting the following functions to use correct folio
sizes/shifts:

- zlib_compress_folios()
- zlib_decompress_bio()

There is a special handling for s390 hardware acceleration.
With bs > ps cases, we can go with 16K block size on s390 (which uses
fixed 4K page size).
In that case we do not need to do the buffer copy as our folio is large
enough for hardware acceleration.

So factor out the s390 specific and folio size check into a helper,
need_special_buffer().

Signed-off-by: Qu Wenruo <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: adam900710

fs/btrfs/zlib.c

@@ -53,6 +53,22 @@ void zlib_free_workspace(struct list_head *ws)
 	kfree(workspace);
 }
 
+/*
+ * For s390 hardware acceleration, the buffer size should be at least
+ * ZLIB_DFLTCC_BUF_SIZE to achieve the best performance.
+ *
+ * But if bs > ps we can have large enough folios that meet the s390 hardware
+ * handling.
+ */
+static bool need_special_buffer(struct btrfs_fs_info *fs_info)
+{
+	if (!zlib_deflate_dfltcc_enabled())
+		return false;
+	if (btrfs_min_folio_size(fs_info) >= ZLIB_DFLTCC_BUF_SIZE)
+		return false;
+	return true;
+}
+
 struct list_head *zlib_alloc_workspace(struct btrfs_fs_info *fs_info, unsigned int level)
 {
 	const u32 blocksize = fs_info->sectorsize;
@@ -68,11 +84,7 @@ struct list_head *zlib_alloc_workspace(struct btrfs_fs_info *fs_info, unsigned i
 	workspace->strm.workspace = kvzalloc(workspacesize, GFP_KERNEL | __GFP_NOWARN);
 	workspace->level = level;
 	workspace->buf = NULL;
-	/*
-	 * In case of s390 zlib hardware support, allocate lager workspace
-	 * buffer. If allocator fails, fall back to a single page buffer.
-	 */
-	if (zlib_deflate_dfltcc_enabled()) {
+	if (need_special_buffer(fs_info)) {
 		workspace->buf = kmalloc(ZLIB_DFLTCC_BUF_SIZE,
 					 __GFP_NOMEMALLOC | __GFP_NORETRY |
 					 __GFP_NOWARN | GFP_NOIO);
@@ -139,6 +151,8 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
 	struct address_space *mapping = inode->vfs_inode.i_mapping;
+	const u32 min_folio_shift = PAGE_SHIFT + fs_info->block_min_order;
+	const u32 min_folio_size = btrfs_min_folio_size(fs_info);
 	int ret;
 	char *data_in = NULL;
 	char *cfolio_out;
@@ -147,7 +161,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 	struct folio *out_folio = NULL;
 	unsigned long len = *total_out;
 	unsigned long nr_dest_folios = *out_folios;
-	const unsigned long max_out = nr_dest_folios * PAGE_SIZE;
+	const unsigned long max_out = nr_dest_folios << min_folio_shift;
 	const u32 blocksize = fs_info->sectorsize;
 	const u64 orig_end = start + len;
 
@@ -179,7 +193,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 	workspace->strm.next_in = workspace->buf;
 	workspace->strm.avail_in = 0;
 	workspace->strm.next_out = cfolio_out;
-	workspace->strm.avail_out = PAGE_SIZE;
+	workspace->strm.avail_out = min_folio_size;
 
 	while (workspace->strm.total_in < len) {
 		/*
@@ -191,10 +205,11 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 			unsigned int copy_length = min(bytes_left, workspace->buf_size);
 
 			/*
-			 * This can only happen when hardware zlib compression is
-			 * enabled.
+			 * For s390 hardware accelerated zlib, and our folio is smaller
+			 * than the copy_length, we need to fill the buffer so that
+			 * we can take full advantage of hardware acceleration.
 			 */
-			if (copy_length > PAGE_SIZE) {
+			if (need_special_buffer(fs_info)) {
 				ret = copy_data_into_buffer(mapping, workspace,
 							    start, copy_length);
 				if (ret < 0)
@@ -258,7 +273,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 			cfolio_out = folio_address(out_folio);
 			folios[nr_folios] = out_folio;
 			nr_folios++;
-			workspace->strm.avail_out = PAGE_SIZE;
+			workspace->strm.avail_out = min_folio_size;
 			workspace->strm.next_out = cfolio_out;
 		}
 		/* we're all done */
@@ -294,7 +309,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 			cfolio_out = folio_address(out_folio);
 			folios[nr_folios] = out_folio;
 			nr_folios++;
-			workspace->strm.avail_out = PAGE_SIZE;
+			workspace->strm.avail_out = min_folio_size;
 			workspace->strm.next_out = cfolio_out;
 		}
 	}
@@ -320,20 +335,22 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 
 int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 {
+	struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
+	const u32 min_folio_size = btrfs_min_folio_size(fs_info);
 	int ret = 0, ret2;
 	int wbits = MAX_WBITS;
 	char *data_in;
 	size_t total_out = 0;
 	unsigned long folio_in_index = 0;
 	size_t srclen = cb->compressed_len;
-	unsigned long total_folios_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
+	unsigned long total_folios_in = DIV_ROUND_UP(srclen, min_folio_size);
 	unsigned long buf_start;
 	struct folio **folios_in = cb->compressed_folios;
 
 	data_in = kmap_local_folio(folios_in[folio_in_index], 0);
 	workspace->strm.next_in = data_in;
-	workspace->strm.avail_in = min_t(size_t, srclen, PAGE_SIZE);
+	workspace->strm.avail_in = min_t(size_t, srclen, min_folio_size);
 	workspace->strm.total_in = 0;
 
 	workspace->strm.total_out = 0;
@@ -394,7 +411,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			data_in = kmap_local_folio(folios_in[folio_in_index], 0);
 			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, min_folio_size);
 		}
 	}
 	if (unlikely(ret != Z_STREAM_END)) {