f2fs: allocate proper size memory for zstd decompress

As 5kft <5kft@5kft.org> reported:

 kworker/u9:3: page allocation failure: order:9, mode:0x40c40(GFP_NOFS|__GFP_COMP), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 3 PID: 8168 Comm: kworker/u9:3 Tainted: G         C        5.8.3-sunxi #trunk
 Hardware name: Allwinner sun8i Family
 Workqueue: f2fs_post_read_wq f2fs_post_read_work
 [<c010d6d5>] (unwind_backtrace) from [<c0109a55>] (show_stack+0x11/0x14)
 [<c0109a55>] (show_stack) from [<c056d489>] (dump_stack+0x75/0x84)
 [<c056d489>] (dump_stack) from [<c0243b53>] (warn_alloc+0xa3/0x104)
 [<c0243b53>] (warn_alloc) from [<c024473b>] (__alloc_pages_nodemask+0xb87/0xc40)
 [<c024473b>] (__alloc_pages_nodemask) from [<c02267c5>] (kmalloc_order+0x19/0x38)
 [<c02267c5>] (kmalloc_order) from [<c02267fd>] (kmalloc_order_trace+0x19/0x90)
 [<c02267fd>] (kmalloc_order_trace) from [<c047c665>] (zstd_init_decompress_ctx+0x21/0x88)
 [<c047c665>] (zstd_init_decompress_ctx) from [<c047e9cf>] (f2fs_decompress_pages+0x97/0x228)
 [<c047e9cf>] (f2fs_decompress_pages) from [<c045d0ab>] (__read_end_io+0xfb/0x130)
 [<c045d0ab>] (__read_end_io) from [<c045d141>] (f2fs_post_read_work+0x61/0x84)
 [<c045d141>] (f2fs_post_read_work) from [<c0130b2f>] (process_one_work+0x15f/0x3b0)
 [<c0130b2f>] (process_one_work) from [<c0130e7b>] (worker_thread+0xfb/0x3e0)
 [<c0130e7b>] (worker_thread) from [<c0135c3b>] (kthread+0xeb/0x10c)
 [<c0135c3b>] (kthread) from [<c0100159>]

zstd may allocate large size memory for {,de}compression, it may cause
file copy failure on low-end device which has very few memory.

For decompression, let's just allocate proper size memory based on current
file's cluster size instead of max cluster size.
Reported-by: 5kft <5kft@5kft.org>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/compress.c

@@ -382,16 +382,17 @@ static int zstd_init_decompress_ctx(struct decompress_io_ctx *dic)
 	ZSTD_DStream *stream;
 	void *workspace;
 	unsigned int workspace_size;
+	unsigned int max_window_size =
+			MAX_COMPRESS_WINDOW_SIZE(dic->log_cluster_size);
 
-	workspace_size = ZSTD_DStreamWorkspaceBound(MAX_COMPRESS_WINDOW_SIZE);
+	workspace_size = ZSTD_DStreamWorkspaceBound(max_window_size);
 
 	workspace = f2fs_kvmalloc(F2FS_I_SB(dic->inode),
 					workspace_size, GFP_NOFS);
 	if (!workspace)
 		return -ENOMEM;
 
-	stream = ZSTD_initDStream(MAX_COMPRESS_WINDOW_SIZE,
-					workspace, workspace_size);
+	stream = ZSTD_initDStream(max_window_size, workspace, workspace_size);
 	if (!stream) {
 		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_initDStream failed\n",
 				KERN_ERR, F2FS_I_SB(dic->inode)->sb->s_id,

fs/f2fs/f2fs.h

@@ -1419,7 +1419,7 @@ struct decompress_io_ctx {
 #define NULL_CLUSTER			((unsigned int)(~0))
 #define MIN_COMPRESS_LOG_SIZE		2
 #define MAX_COMPRESS_LOG_SIZE		8
-#define MAX_COMPRESS_WINDOW_SIZE	((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
+#define MAX_COMPRESS_WINDOW_SIZE(log_size)	((PAGE_SIZE) << (log_size))
 
 struct f2fs_sb_info {
 	struct super_block *sb;			/* pointer to VFS super block */