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Message-ID: <fa2eeb31-9579-a4a4-71b3-200509da1ed9@kernel.org>
Date: Tue, 9 Nov 2021 21:27:25 +0800
From: Chao Yu <chao@...nel.org>
To: Huang Jianan <huangjianan@...o.com>, linux-erofs@...ts.ozlabs.org
Cc: zhangshiming@...o.com, linux-kernel@...r.kernel.org, yh@...o.com,
guanyuwei@...o.com, guoweichao@...o.com
Subject: Re: [PATCH v2 2/2] erofs: add sysfs node to control sync
decompression strategy
On 2021/11/9 15:45, Huang Jianan via Linux-erofs wrote:
> Although readpage is a synchronous path, there will be no additional
> kworker scheduling overhead in non-atomic contexts. So add a sysfs
> node to allow disable sync decompression.
>
> Signed-off-by: Huang Jianan <huangjianan@...o.com>
> ---
> changes since v1:
> - leave auto default
> - add a disable strategy for sync_decompress
>
> Documentation/ABI/testing/sysfs-fs-erofs | 9 +++++++++
> fs/erofs/internal.h | 4 ++--
> fs/erofs/super.c | 2 +-
> fs/erofs/sysfs.c | 10 ++++++++++
> fs/erofs/zdata.c | 19 ++++++++++++++-----
> 5 files changed, 36 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
> index 86d0d0234473..c84f12004f02 100644
> --- a/Documentation/ABI/testing/sysfs-fs-erofs
> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
> @@ -5,3 +5,12 @@ Description: Shows all enabled kernel features.
> Supported features:
> lz4_0padding, compr_cfgs, big_pcluster, device_table,
> sb_chksum.
> +
> +What: /sys/fs/erofs/<disk>/sync_decompress
> +Date: November 2021
> +Contact: "Huang Jianan" <huangjianan@...o.com>
> +Description: Control strategy of sync decompression
> + - 0 (defalut, auto): enable for readpage, and enable for
> + readahead on atomic contexts only,
> + - 1 (force on): enable for readpage and readahead.
> + - 2 (disable): disable for all situations.
1 (force on)
2 (force off)
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index d0cd712dc222..06a8bbdb378f 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -60,8 +60,8 @@ 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 - disable) */
Ditto,
> + unsigned int sync_decompress;
>
> /* threshold for decompression synchronously */
> unsigned int max_sync_decompress_pages;
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index abc1da5d1719..ea223d6c7985 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -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 = 0;
> #endif
> #ifdef CONFIG_EROFS_FS_XATTR
> set_opt(&ctx->opt, XATTR_USER);
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index dd328d20c451..a8889b2b65f3 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -16,6 +16,7 @@ enum {
>
> enum {
> struct_erofs_sb_info,
> + struct_erofs_mount_opts,
> };
>
> struct erofs_attr {
> @@ -55,7 +56,10 @@ static struct erofs_attr erofs_attr_##_name = { \
>
> #define ATTR_LIST(name) (&erofs_attr_##name.attr)
>
> +EROFS_ATTR_RW_UI(sync_decompress, erofs_mount_opts);
> +
> static struct attribute *erofs_attrs[] = {
> + ATTR_LIST(sync_decompress),
> NULL,
> };
> ATTRIBUTE_GROUPS(erofs);
> @@ -82,6 +86,8 @@ 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;
> }
>
> @@ -126,6 +132,10 @@ static ssize_t erofs_attr_store(struct kobject *kobj, struct attribute *attr,
> ret = kstrtoul(skip_spaces(buf), 0, &t);
> if (ret)
> return ret;
> +
> + if (!strcmp(a->attr.name, "sync_decompress") && (t > 2))
if (!strcmp()) {
if (t > 2)
return -EINVAL;
*((unsigned int *) ptr) = t;
return len;
}
How about adding enum instead of raw numbers to improve readability?
Thanks,
> + return -EINVAL;
> +
> *((unsigned int *) ptr) = t;
> return len;
> case attr_pointer_bool:
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index bcb1b91b234f..70ec51fa7131 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -794,7 +794,8 @@ 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;
> + if (sbi->opt.sync_decompress == 0)
> + sbi->opt.sync_decompress = 1;
> return;
> }
> z_erofs_decompressqueue_work(&io->u.work);
> @@ -1454,9 +1455,11 @@ 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;
> + bool force_fg = true;
>
> trace_erofs_readpage(page, false);
> f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
> @@ -1468,8 +1471,11 @@ static int z_erofs_readpage(struct file *file, struct page *page)
>
> (void)z_erofs_collector_end(&f.clt);
>
> + if (sbi->opt.sync_decompress == 2)
> + force_fg = false;
> +
> /* 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, force_fg);
>
> if (err)
> erofs_err(inode->i_sb, "failed to read, err [%d]", err);
> @@ -1488,6 +1494,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
> struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
> struct page *pagepool = NULL, *head = NULL, *page;
> unsigned int nr_pages;
> + bool force_fg = false;
>
> f.readahead = true;
> f.headoffset = readahead_pos(rac);
> @@ -1519,9 +1526,11 @@ static void z_erofs_readahead(struct readahead_control *rac)
> z_erofs_pcluster_readmore(&f, rac, 0, &pagepool, false);
> (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);
> + if (sbi->opt.sync_decompress == 1)
> + force_fg = true;
> +
> + z_erofs_runqueue(inode->i_sb, &f, &pagepool, force_fg
> + && nr_pages <= sbi->opt.max_sync_decompress_pages);
> if (f.map.mpage)
> put_page(f.map.mpage);
> erofs_release_pages(&pagepool);
>
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