erofs: use meta buffers for super operations

Get rid of old erofs_get_meta_page() within super operations by
using on-stack meta buffers in order to prepare subpage and folio
features.

Link: https://lore.kernel.org/r/20220102081317.109797-1-hsiangkao@linux.alibaba.com
Reviewed-by: Yue Hu <huyue2@yulong.com>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 0724ad5fd6cfd67c72f8106aab709029f4db8fe3..5c137647fa8a2d0554d1dd2da30c762400021dae 100644 (file)
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2017-2018 HUAWEI, Inc.
  *             https://www.huawei.com/
+ * Copyright (C) 2021, Alibaba Cloud
  */
 #include <linux/module.h>
 #include <linux/buffer_head.h>
@@ -124,80 +125,50 @@ static bool check_layout_compatibility(struct super_block *sb,
 
 #ifdef CONFIG_EROFS_FS_ZIP
 /* read variable-sized metadata, offset will be aligned by 4-byte */
-static void *erofs_read_metadata(struct super_block *sb, struct page **pagep,
+static void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
                                 erofs_off_t *offset, int *lengthp)
 {
-       struct page *page = *pagep;
        u8 *buffer, *ptr;
        int len, i, cnt;
-       erofs_blk_t blk;
 
        *offset = round_up(*offset, 4);
-       blk = erofs_blknr(*offset);
+       ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*offset), EROFS_KMAP);
+       if (IS_ERR(ptr))
+               return ptr;
 
-       if (!page || page->index != blk) {
-               if (page) {
-                       unlock_page(page);
-                       put_page(page);
-               }
-               page = erofs_get_meta_page(sb, blk);
-               if (IS_ERR(page))
-                       goto err_nullpage;
-       }
-
-       ptr = kmap(page);
        len = le16_to_cpu(*(__le16 *)&ptr[erofs_blkoff(*offset)]);
        if (!len)
                len = U16_MAX + 1;
        buffer = kmalloc(len, GFP_KERNEL);
-       if (!buffer) {
-               buffer = ERR_PTR(-ENOMEM);
-               goto out;
-       }
+       if (!buffer)
+               return ERR_PTR(-ENOMEM);
        *offset += sizeof(__le16);
        *lengthp = len;
 
        for (i = 0; i < len; i += cnt) {
                cnt = min(EROFS_BLKSIZ - (int)erofs_blkoff(*offset), len - i);
-               blk = erofs_blknr(*offset);
-
-               if (!page || page->index != blk) {
-                       if (page) {
-                               kunmap(page);
-                               unlock_page(page);
-                               put_page(page);
-                       }
-                       page = erofs_get_meta_page(sb, blk);
-                       if (IS_ERR(page)) {
-                               kfree(buffer);
-                               goto err_nullpage;
-                       }
-                       ptr = kmap(page);
+               ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*offset),
+                                        EROFS_KMAP);
+               if (IS_ERR(ptr)) {
+                       kfree(buffer);
+                       return ptr;
                }
                memcpy(buffer + i, ptr + erofs_blkoff(*offset), cnt);
                *offset += cnt;
        }
-out:
-       kunmap(page);
-       *pagep = page;
        return buffer;
-err_nullpage:
-       *pagep = NULL;
-       return page;
 }
 
 static int erofs_load_compr_cfgs(struct super_block *sb,
                                 struct erofs_super_block *dsb)
 {
-       struct erofs_sb_info *sbi;
-       struct page *page;
+       struct erofs_sb_info *sbi = EROFS_SB(sb);
+       struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
        unsigned int algs, alg;
        erofs_off_t offset;
-       int size, ret;
+       int size, ret = 0;
 
-       sbi = EROFS_SB(sb);
        sbi->available_compr_algs = le16_to_cpu(dsb->u1.available_compr_algs);
-
        if (sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS) {
                erofs_err(sb, "try to load compressed fs with unsupported algorithms %x",
                          sbi->available_compr_algs & ~Z_EROFS_ALL_COMPR_ALGS);
@@ -205,20 +176,17 @@ static int erofs_load_compr_cfgs(struct super_block *sb,
        }
 
        offset = EROFS_SUPER_OFFSET + sbi->sb_size;
-       page = NULL;
        alg = 0;
-       ret = 0;
-
        for (algs = sbi->available_compr_algs; algs; algs >>= 1, ++alg) {
                void *data;
 
                if (!(algs & 1))
                        continue;
 
-               data = erofs_read_metadata(sb, &page, &offset, &size);
+               data = erofs_read_metadata(sb, &buf, &offset, &size);
                if (IS_ERR(data)) {
                        ret = PTR_ERR(data);
-                       goto err;
+                       break;
                }
 
                switch (alg) {
@@ -234,13 +202,9 @@ static int erofs_load_compr_cfgs(struct super_block *sb,
                }
                kfree(data);
                if (ret)
-                       goto err;
-       }
-err:
-       if (page) {
-               unlock_page(page);
-               put_page(page);
+                       break;
        }
+       erofs_put_metabuf(&buf);
        return ret;
 }
 #else
@@ -261,7 +225,7 @@ static int erofs_init_devices(struct super_block *sb,
        struct erofs_sb_info *sbi = EROFS_SB(sb);
        unsigned int ondisk_extradevs;
        erofs_off_t pos;
-       struct page *page = NULL;
+       struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
        struct erofs_device_info *dif;
        struct erofs_deviceslot *dis;
        void *ptr;
@@ -285,22 +249,13 @@ static int erofs_init_devices(struct super_block *sb,
        pos = le16_to_cpu(dsb->devt_slotoff) * EROFS_DEVT_SLOT_SIZE;
        down_read(&sbi->devs->rwsem);
        idr_for_each_entry(&sbi->devs->tree, dif, id) {
-               erofs_blk_t blk = erofs_blknr(pos);
                struct block_device *bdev;
 
-               if (!page || page->index != blk) {
-                       if (page) {
-                               kunmap(page);
-                               unlock_page(page);
-                               put_page(page);
-                       }
-
-                       page = erofs_get_meta_page(sb, blk);
-                       if (IS_ERR(page)) {
-                               up_read(&sbi->devs->rwsem);
-                               return PTR_ERR(page);
-                       }
-                       ptr = kmap(page);
+               ptr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos),
+                                        EROFS_KMAP);
+               if (IS_ERR(ptr)) {
+                       err = PTR_ERR(ptr);
+                       break;
                }
                dis = ptr + erofs_blkoff(pos);
 
@@ -309,7 +264,7 @@ static int erofs_init_devices(struct super_block *sb,
                                          sb->s_type);
                if (IS_ERR(bdev)) {
                        err = PTR_ERR(bdev);
-                       goto err_out;
+                       break;
                }
                dif->bdev = bdev;
                dif->dax_dev = fs_dax_get_by_bdev(bdev);
@@ -318,13 +273,8 @@ static int erofs_init_devices(struct super_block *sb,
                sbi->total_blocks += dif->blocks;
                pos += EROFS_DEVT_SLOT_SIZE;
        }
-err_out:
        up_read(&sbi->devs->rwsem);
-       if (page) {
-               kunmap(page);
-               unlock_page(page);
-               put_page(page);
-       }
+       erofs_put_metabuf(&buf);
        return err;
 }