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>

1 files changed, 27 insertions, 77 deletions

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 0724ad5fd6cf..5c137647fa8a 100644
--- 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;
 }