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Date: Sun, 2 Jan 2022 16:15:49 +0800
From: Liu Bo <bo.liu@...ux.alibaba.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc: linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, Yue Hu <huyue2@...ong.com>
Subject: Re: [PATCH v3 3/5] erofs: use meta buffers for super operations
On Sun, Jan 02, 2022 at 04:13:17PM +0800, Gao Xiang wrote:
> 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.
>
Reviewed-by: Liu Bo <bo.liu@...ux.alibaba.com>
> Reviewed-by: Yue Hu <huyue2@...ong.com>
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> ---
> changes since v2:
> - add a missing kfree(buffer);
> - forget to put_metabuf in erofs_load_compr_cfgs;
> - fotget to put_metabuf in erofs_init_devices.
>
> fs/erofs/super.c | 104 ++++++++++++-----------------------------------
> 1 file 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;
> }
>
> --
> 2.24.4
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