Commit 40452ffc authored by Huang Jianan's avatar Huang Jianan Committed by Gao Xiang
Browse files

erofs: add sysfs node to control sync decompression strategy 

Although readpage is a synchronous path, there will be no additional
kworker scheduling overhead in non-atomic contexts together with
dm-verity.

Let's add a sysfs node to disable sync decompression as an option.

Link: https://lore.kernel.org/r/20211206143552.8384-1-huangjianan@oppo.com


Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarHuang Jianan <huangjianan@oppo.com>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
parent 168e9a76

Documentation/ABI/testing/sysfs-fs-erofs

+9 −0
Original line number Diff line number Diff line
@@ -5,3 +5,12 @@ Description: Shows all enabled kernel features. 
		Supported features:

		zero_padding, compr_cfgs, big_pcluster, chunked_file,

		device_table, compr_head2, sb_chksum.



What:		/sys/fs/erofs/<disk>/sync_decompress

Date:		November 2021

Contact:	"Huang Jianan" <huangjianan@oppo.com>

Description:	Control strategy of sync decompression

		- 0 (default, auto): enable for readpage, and enable for

				     readahead on atomic contexts only,

		- 1 (force on): enable for readpage and readahead.

		- 2 (force off): disable for all situations.

fs/erofs/internal.h

+8 −2
Original line number Diff line number Diff line
@@ -56,12 +56,18 @@ struct erofs_device_info { 
	u32 mapped_blkaddr;

};



enum {

	EROFS_SYNC_DECOMPRESS_AUTO,

	EROFS_SYNC_DECOMPRESS_FORCE_ON,

	EROFS_SYNC_DECOMPRESS_FORCE_OFF

};



struct erofs_mount_opts {

#ifdef CONFIG_EROFS_FS_ZIP

	/* current strategy of how to use managed cache */

	unsigned char cache_strategy;

	/* strategy of sync decompression (false - auto, true - force on) */

	bool readahead_sync_decompress;

	/* strategy of sync decompression (0 - auto, 1 - force on, 2 - force off) */

	unsigned int sync_decompress;



	/* threshold for decompression synchronously */

	unsigned int max_sync_decompress_pages;

fs/erofs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -423,7 +423,7 @@ static void erofs_default_options(struct erofs_fs_context *ctx) 
#ifdef CONFIG_EROFS_FS_ZIP

	ctx->opt.cache_strategy = EROFS_ZIP_CACHE_READAROUND;

	ctx->opt.max_sync_decompress_pages = 3;

	ctx->opt.readahead_sync_decompress = false;

	ctx->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_AUTO;

#endif

#ifdef CONFIG_EROFS_FS_XATTR

	set_opt(&ctx->opt, XATTR_USER);

fs/erofs/sysfs.c

+15 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ enum { 


enum {

	struct_erofs_sb_info,

	struct_erofs_mount_opts,

};



struct erofs_attr {
@@ -54,7 +55,14 @@ static struct erofs_attr erofs_attr_##_name = { \ 


#define ATTR_LIST(name) (&erofs_attr_##name.attr)



#ifdef CONFIG_EROFS_FS_ZIP

EROFS_ATTR_RW_UI(sync_decompress, erofs_mount_opts);

#endif



static struct attribute *erofs_attrs[] = {

#ifdef CONFIG_EROFS_FS_ZIP

	ATTR_LIST(sync_decompress),

#endif

	NULL,

};

ATTRIBUTE_GROUPS(erofs);
@@ -85,6 +93,8 @@ static unsigned char *__struct_ptr(struct erofs_sb_info *sbi, 
{

	if (struct_type == struct_erofs_sb_info)

		return (unsigned char *)sbi + offset;

	if (struct_type == struct_erofs_mount_opts)

		return (unsigned char *)&sbi->opt + offset;

	return NULL;

}
@@ -130,6 +140,11 @@ static ssize_t erofs_attr_store(struct kobject *kobj, struct attribute *attr, 
			return ret;

		if (t != (unsigned int)t)

			return -ERANGE;

#ifdef CONFIG_EROFS_FS_ZIP

		if (!strcmp(a->attr.name, "sync_decompress") &&

		    (t > EROFS_SYNC_DECOMPRESS_FORCE_OFF))

			return -EINVAL;

#endif

		*(unsigned int *)ptr = t;

		return len;

	case attr_pointer_bool:

fs/erofs/zdata.c

+22 −4
Original line number Diff line number Diff line
@@ -762,6 +762,21 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe, 
	goto out;

}



static bool z_erofs_get_sync_decompress_policy(struct erofs_sb_info *sbi,

				       unsigned int readahead_pages)

{

	/* auto: enable for readpage, disable for readahead */

	if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&

	    !readahead_pages)

		return true;



	if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&

	    (readahead_pages <= sbi->opt.max_sync_decompress_pages))

		return true;



	return false;

}



static void z_erofs_decompressqueue_work(struct work_struct *work);

static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,

				       bool sync, int bios)
@@ -784,7 +799,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io, 
	/* Use workqueue and sync decompression for atomic contexts only */

	if (in_atomic() || irqs_disabled()) {

		queue_work(z_erofs_workqueue, &io->u.work);

		sbi->opt.readahead_sync_decompress = true;

		/* enable sync decompression for readahead */

		if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)

			sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;

		return;

	}

	z_erofs_decompressqueue_work(&io->u.work);
@@ -1435,6 +1452,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f, 
static int z_erofs_readpage(struct file *file, struct page *page)

{

	struct inode *const inode = page->mapping->host;

	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);

	struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);

	struct page *pagepool = NULL;

	int err;
@@ -1450,7 +1468,8 @@ static int z_erofs_readpage(struct file *file, struct page *page) 
	(void)z_erofs_collector_end(&f.clt);



	/* if some compressed cluster ready, need submit them anyway */

	z_erofs_runqueue(inode->i_sb, &f, &pagepool, true);

	z_erofs_runqueue(inode->i_sb, &f, &pagepool,

			 z_erofs_get_sync_decompress_policy(sbi, 0));



	if (err)

		erofs_err(inode->i_sb, "failed to read, err [%d]", err);
@@ -1501,8 +1520,7 @@ static void z_erofs_readahead(struct readahead_control *rac) 
	(void)z_erofs_collector_end(&f.clt);



	z_erofs_runqueue(inode->i_sb, &f, &pagepool,

			 sbi->opt.readahead_sync_decompress &&

			 nr_pages <= sbi->opt.max_sync_decompress_pages);

			 z_erofs_get_sync_decompress_policy(sbi, nr_pages));

	if (f.map.mpage)

		put_page(f.map.mpage);

	erofs_release_pages(&pagepool);