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: Chao Yu <chao@kernel.org>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
index a9512594dc4ca0d41e670fad6b61bea726a95ee2..05482374a741bd100c62a062a3686e8811199526 100644 (file)
--- 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:
                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.

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 43f0332fa4892d2aa7729806fd16070948094fff..8e70435629e58b39f1d4e4cccfcc13e65c347489 100644 (file)
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -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;

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index abc1da5d1719cc462b0a3fa8ae1f93d6abc88431..58f381f80205785a73eccce7e26030716fbd6652 100644 (file)
--- 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 = EROFS_SYNC_DECOMPRESS_AUTO;
 #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 33e15fa63c82d91bb7a1c0cc87d2ea1cb0094d2e..66669343210702bc3a5211426b9855a8b6165145 100644 (file)
--- 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 {
@@ -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:

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 9a249bfc2770581dd91cbcf212c2d2e7a7bbfd8a..bc765d8a6dc24c1f085fc55266a7eebe4004ff7f 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -762,6 +762,21 @@ err_out:
        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 @@ skip:
 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);