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Subject[PATCH 3/5] erofs: use meta buffers for super operations
Date
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.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
fs/erofs/super.c | 105 ++++++++++++-----------------------------------
1 file changed, 26 insertions(+), 79 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 0724ad5fd6cf..38305fa2969b 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 +125,48 @@ 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))
+ 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);
@@ -205,21 +174,16 @@ 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);
- if (IS_ERR(data)) {
- ret = PTR_ERR(data);
- goto err;
- }
+ data = erofs_read_metadata(sb, &buf, &offset, &size);
+ if (IS_ERR(data))
+ return PTR_ERR(data);

switch (alg) {
case Z_EROFS_COMPRESSION_LZ4:
@@ -234,13 +198,9 @@ 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 +221,7 @@ 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 +245,13 @@ 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)) {
+ up_read(&sbi->devs->rwsem);
+ return PTR_ERR(ptr);
}
dis = ptr + erofs_blkoff(pos);

@@ -320,11 +271,7 @@ static int erofs_init_devices(struct super_block *sb,
}
err_out:
up_read(&sbi->devs->rwsem);
- if (page) {
- kunmap(page);
- unlock_page(page);
- put_page(page);
- }
+ erofs_put_metabuf(&buf);
return err;
}

--
2.24.4
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