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Subject: Re: [PATCH RFC v2 for-6.8/block 11/18] erofs: use bdev api
To:     Gao Xiang <hsiangkao@linux.alibaba.com>,
        Yu Kuai <yukuai1@huaweicloud.com>, axboe@kernel.dk,
        roger.pau@citrix.com, colyli@suse.de, kent.overstreet@gmail.com,
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        vigneshr@ti.com, sth@linux.ibm.com, hoeppner@linux.ibm.com,
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        jejb@linux.ibm.com, martin.petersen@oracle.com, clm@fb.com,
        josef@toxicpanda.com, dsterba@suse.com, viro@zeniv.linux.org.uk,
        brauner@kernel.org, nico@fluxnic.net, xiang@kernel.org,
        chao@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca,
        agruenba@redhat.com, jack@suse.com, konishi.ryusuke@gmail.com,
        willy@infradead.org, akpm@linux-foundation.org,
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        linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org,
        gfs2@lists.linux.dev, linux-nilfs@vger.kernel.org,
        yi.zhang@huawei.com, yangerkun@huawei.com,
        "yukuai (C)" <yukuai3@huawei.com>
References: <20231211140552.973290-1-yukuai1@huaweicloud.com>
 <20231211140722.974745-1-yukuai1@huaweicloud.com>
 <1812c1bf-08b5-46a5-a633-12470e2c8f18@linux.alibaba.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <7465ebce-1290-e258-13cf-146fa4fd6302@huaweicloud.com>
Date:   Tue, 12 Dec 2023 14:49:39 +0800
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Hi,

在 2023/12/12 14:35, Gao Xiang 写道:
> 
> 
> On 2023/12/11 22:07, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Avoid to access bd_inode directly, prepare to remove bd_inode from
>> block_devcie.
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>>   fs/erofs/data.c     | 18 ++++++++++++------
>>   fs/erofs/internal.h |  2 ++
>>   2 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
>> index c98aeda8abb2..8cf3618190ab 100644
>> --- a/fs/erofs/data.c
>> +++ b/fs/erofs/data.c
>> @@ -32,8 +32,7 @@ void erofs_put_metabuf(struct erofs_buf *buf)
>>   void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
>>             enum erofs_kmap_type type)
>>   {
>> -    struct inode *inode = buf->inode;
>> -    erofs_off_t offset = (erofs_off_t)blkaddr << inode->i_blkbits;
>> +    erofs_off_t offset = (erofs_off_t)blkaddr << buf->blkszbits;
> I'd suggest that use `buf->blkszbits` only for bdev_read_folio() since
> erofs_init_metabuf() is not always called before erofs_bread() is used.
> 
> For example, buf->inode can be one of directory inodes other than
> initialized by erofs_init_metabuf().

Thanks for the notice, and you're right, I'll update code in v3:

u8 blkszbits = buf->inode ? inode->i_blkbits : buf->blkszbits;
erofs_off_t offset = (erofs_off_t)blkaddr << blkszbits;

Kuai
> 
> Thanks,
> Gao Xiang
> 
> 
>>       pgoff_t index = offset >> PAGE_SHIFT;
>>       struct page *page = buf->page;
>>       struct folio *folio;
>> @@ -43,7 +42,9 @@ void *erofs_bread(struct erofs_buf *buf, erofs_blk_t 
>> blkaddr,
>>           erofs_put_metabuf(buf);
>>           nofs_flag = memalloc_nofs_save();
>> -        folio = read_cache_folio(inode->i_mapping, index, NULL, NULL);
>> +        folio = buf->inode ?
>> +            read_mapping_folio(buf->inode->i_mapping, index, NULL) :
>> +            bdev_read_folio(buf->bdev, offset);
>>           memalloc_nofs_restore(nofs_flag);
>>           if (IS_ERR(folio))
>>               return folio;
>> @@ -67,10 +68,15 @@ void *erofs_bread(struct erofs_buf *buf, 
>> erofs_blk_t blkaddr,
>>   void erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb)
>>   {
>> -    if (erofs_is_fscache_mode(sb))
>> +    if (erofs_is_fscache_mode(sb)) {
>>           buf->inode = EROFS_SB(sb)->s_fscache->inode;
>> -    else
>> -        buf->inode = sb->s_bdev->bd_inode;
>> +        buf->bdev = NULL;
>> +        buf->blkszbits = buf->inode->i_blkbits;
>> +    } else {
>> +        buf->inode = NULL;
>> +        buf->bdev = sb->s_bdev;
>> +        buf->blkszbits = EROFS_SB(sb)->blkszbits;
>> +    }
>>   }
>>   void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index b0409badb017..c9206351b485 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -224,8 +224,10 @@ enum erofs_kmap_type {
>>   struct erofs_buf {
>>       struct inode *inode;
>> +    struct block_device *bdev;
>>       struct page *page;
>>       void *base;
>> +    u8 blkszbits;
>>       enum erofs_kmap_type kmap_type;
>>   };
>>   #define __EROFS_BUF_INITIALIZER    ((struct erofs_buf){ .page = NULL })
> .
>