squashfs: add the mount parameter theads=<single|multi|percpu>

Patch series 'squashfs: Add the mount parameter "threads="'.

Currently, Squashfs supports multiple decompressor parallel modes. 
However, this mode can be configured only during kernel building and does
not support flexible selection during runtime.

In the current patch set, the mount parameter "threads=" is added to allow
users to select the parallel decompressor mode and configure the number of
decompressors when mounting a file system.

"threads=<single|multi|percpu|1|2|3|...>"
The upper limit is num_online_cpus() * 2.


This patch (of 2):

Squashfs supports three decompression concurrency modes:
	Single-thread mode: concurrent reads are blocked and the memory
		overhead is small.
	Multi-thread mode/percpu mode: reduces concurrent read blocking but
		increases memory overhead.

The corresponding schema must be fixed at compile time. During mounting,
the concurrent decompression mode cannot be adjusted based on file read
blocking.

The mount parameter theads=<single|multi|percpu> is added to select
the concurrent decompression mode of a single SquashFS file system
image.

Link: https://lkml.kernel.org/r/20221019030930.130456-1-nixiaoming@huawei.com
Link: https://lkml.kernel.org/r/20221019030930.130456-2-nixiaoming@huawei.com
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Reviewed-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Jianguo Chen <chenjianguo3@huawei.com>
Cc: Jubin Zhong <zhongjubin@huawei.com>
Cc: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 53 insertions, 3 deletions

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 32565dafa7f3..aac3ea72a9ba 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -47,10 +47,12 @@ enum Opt_errors {
 
 enum squashfs_param {
 	Opt_errors,
+	Opt_threads,
 };
 
 struct squashfs_mount_opts {
 	enum Opt_errors errors;
+	const struct squashfs_decompressor_thread_ops *thread_ops;
 };
 
 static const struct constant_table squashfs_param_errors[] = {
@@ -61,9 +63,29 @@ static const struct constant_table squashfs_param_errors[] = {
 
 static const struct fs_parameter_spec squashfs_fs_parameters[] = {
 	fsparam_enum("errors", Opt_errors, squashfs_param_errors),
+	fsparam_string("threads", Opt_threads),
 	{}
 };
 
+static int squashfs_parse_param_threads(const char *str, struct squashfs_mount_opts *opts)
+{
+#ifdef CONFIG_SQUASHFS_CHOICE_DECOMP_BY_MOUNT
+	if (strcmp(str, "single") == 0) {
+		opts->thread_ops = &squashfs_decompressor_single;
+		return 0;
+	}
+	if (strcmp(str, "multi") == 0) {
+		opts->thread_ops = &squashfs_decompressor_multi;
+		return 0;
+	}
+	if (strcmp(str, "percpu") == 0) {
+		opts->thread_ops = &squashfs_decompressor_percpu;
+		return 0;
+	}
+#endif
+	return -EINVAL;
+}
+
 static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct squashfs_mount_opts *opts = fc->fs_private;
@@ -78,6 +100,10 @@ static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *para
 	case Opt_errors:
 		opts->errors = result.uint_32;
 		break;
+	case Opt_threads:
+		if (squashfs_parse_param_threads(param->string, opts) != 0)
+			return -EINVAL;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -167,6 +193,7 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 			       sb->s_bdev);
 		goto failed_mount;
 	}
+	msblk->thread_ops = opts->thread_ops;
 
 	/* Check the MAJOR & MINOR versions and lookup compression type */
 	msblk->decompressor = supported_squashfs_filesystem(
@@ -252,7 +279,7 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	/* Allocate read_page block */
 	msblk->read_page = squashfs_cache_init("data",
-		squashfs_max_decompressors(), msblk->block_size);
+		msblk->thread_ops->max_decompressors(), msblk->block_size);
 	if (msblk->read_page == NULL) {
 		errorf(fc, "Failed to allocate read_page block");
 		goto failed_mount;
@@ -383,7 +410,7 @@ failed_mount:
 	squashfs_cache_delete(msblk->block_cache);
 	squashfs_cache_delete(msblk->fragment_cache);
 	squashfs_cache_delete(msblk->read_page);
-	squashfs_decompressor_destroy(msblk);
+	msblk->thread_ops->destroy(msblk);
 	kfree(msblk->inode_lookup_table);
 	kfree(msblk->fragment_index);
 	kfree(msblk->id_table);
@@ -435,6 +462,20 @@ static int squashfs_show_options(struct seq_file *s, struct dentry *root)
 	else
 		seq_puts(s, ",errors=continue");
 
+#ifdef CONFIG_SQUASHFS_CHOICE_DECOMP_BY_MOUNT
+	if (msblk->thread_ops == &squashfs_decompressor_single) {
+		seq_puts(s, ",threads=single");
+		return 0;
+	}
+	if (msblk->thread_ops == &squashfs_decompressor_multi) {
+		seq_puts(s, ",threads=multi");
+		return 0;
+	}
+	if (msblk->thread_ops == &squashfs_decompressor_percpu) {
+		seq_puts(s, ",threads=percpu");
+		return 0;
+	}
+#endif
 	return 0;
 }
 
@@ -446,6 +487,15 @@ static int squashfs_init_fs_context(struct fs_context *fc)
 	if (!opts)
 		return -ENOMEM;
 
+#ifdef CONFIG_SQUASHFS_DECOMP_SINGLE
+	opts->thread_ops = &squashfs_decompressor_single;
+#elif defined(CONFIG_SQUASHFS_DECOMP_MULTI)
+	opts->thread_ops = &squashfs_decompressor_multi;
+#elif defined(CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU)
+	opts->thread_ops = &squashfs_decompressor_percpu;
+#else
+#error "fail: unknown squashfs decompression thread mode?"
+#endif
 	fc->fs_private = opts;
 	fc->ops = &squashfs_context_ops;
 	return 0;
@@ -478,7 +528,7 @@ static void squashfs_put_super(struct super_block *sb)
 		squashfs_cache_delete(sbi->block_cache);
 		squashfs_cache_delete(sbi->fragment_cache);
 		squashfs_cache_delete(sbi->read_page);
-		squashfs_decompressor_destroy(sbi);
+		sbi->thread_ops->destroy(sbi);
 		kfree(sbi->id_table);
 		kfree(sbi->fragment_index);
 		kfree(sbi->meta_index);