Re: [PATCH v4 2/2] erofs: set block size to the on-disk block size

[Jingbo Xu]

On 3/6/23 3:31 PM, Yue Hu wrote:
> On Thu,  2 Mar 2023 22:39:15 +0800
> Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx> wrote:
> 
>> Set the block size to that specified in on-disk superblock.
>>
>> Also remove the hard constraint of PAGE_SIZE block size for the
>> uncompressed device backend.  This constraint is temporarily remained
>> for compressed device and fscache backend, as there is more work needed
>> to handle the condition where the block size is not equal to PAGE_SIZE.
>>
>> It is worth noting that the on-disk block size is read prior to
>> erofs_superblock_csum_verify(), as the read block size is needed in the
>> latter.
>>
>> Besides, later we are going to make erofs refer to tar data blobs (which
>> is 512-byte aligned) for OCI containers, where the block size is 512
>> bytes.  In this case, the 512-byte block size may not be adequate for a
>> directory to contain enough dirents.  To fix this, we are also going to
>> introduce directory block size independent on the block size.
>>
>> Due to we have already supported block size smaller than PAGE_SIZE now,
>> disable all these images with such separated directory block size until
>> we supported this feature later.
>>
>> Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
>> ---
>>  fs/erofs/erofs_fs.h |  5 +++--
>>  fs/erofs/inode.c    |  3 ++-
>>  fs/erofs/internal.h | 11 ++---------
>>  fs/erofs/super.c    | 46 +++++++++++++++++++++++++++++----------------
>>  4 files changed, 37 insertions(+), 28 deletions(-)
>>
>> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
>> index dbcd24371002..ac9c2ff3aa66 100644
>> --- a/fs/erofs/erofs_fs.h
>> +++ b/fs/erofs/erofs_fs.h
>> @@ -53,7 +53,7 @@ struct erofs_super_block {
>>  	__le32 magic;           /* file system magic number */
>>  	__le32 checksum;        /* crc32c(super_block) */
>>  	__le32 feature_compat;
>> -	__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
>> +	__u8 blkszbits;         /* filesystem block size */
> 
> /* filesystem block size in bit shift */
> 
>>  	__u8 sb_extslots;	/* superblock size = 128 + sb_extslots * 16 */
>>  
>>  	__le16 root_nid;	/* nid of root directory */
>> @@ -75,7 +75,8 @@ struct erofs_super_block {
>>  	} __packed u1;
>>  	__le16 extra_devices;	/* # of devices besides the primary device */
>>  	__le16 devt_slotoff;	/* startoff = devt_slotoff * devt_slotsize */
>> -	__u8 reserved[6];
>> +	__u8 dirblkbits;	/* directory block size */
> 
> Ditto.
> 
>> +	__u8 reserved[5];
>>  	__le64 packed_nid;	/* nid of the special packed inode */
>>  	__u8 reserved2[24];
>>  };
>> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
>> index de26dac4e07e..0e6ff8a98c68 100644
>> --- a/fs/erofs/inode.c
>> +++ b/fs/erofs/inode.c
>> @@ -291,7 +291,8 @@ static int erofs_fill_inode(struct inode *inode)
>>  	}
>>  
>>  	if (erofs_inode_is_data_compressed(vi->datalayout)) {
>> -		if (!erofs_is_fscache_mode(inode->i_sb))
>> +		if (!erofs_is_fscache_mode(inode->i_sb) &&
>> +		    inode->i_sb->s_blocksize_bits == PAGE_SHIFT)
>>  			err = z_erofs_fill_inode(inode);
>>  		else
>>  			err = -EOPNOTSUPP;
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index d8019d835405..f99ba4061a3b 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -148,7 +148,8 @@ struct erofs_sb_info {
>>  	u16 device_id_mask;	/* valid bits of device id to be used */
>>  
>>  	unsigned char islotbits;	/* inode slot unit size in bit shift */
>> -	unsigned char blkszbits;
>> +	unsigned char blkszbits;	/* filesystem block size */
> 
> Ditto.
> 
>> +	unsigned char dirblkbits;	/* directory block size */
> 
> Ditto.
> 
>>  
>>  	u32 sb_size;			/* total superblock size */
>>  	u32 build_time_nsec;
>> @@ -240,14 +241,6 @@ static inline int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
>>  					VAL != EROFS_LOCKED_MAGIC);
>>  }
>>  
>> -/* we strictly follow PAGE_SIZE and no buffer head yet */
>> -#define LOG_BLOCK_SIZE		PAGE_SHIFT
>> -#define EROFS_BLKSIZ		(1 << LOG_BLOCK_SIZE)
>> -
>> -#if (EROFS_BLKSIZ % 4096 || !EROFS_BLKSIZ)
>> -#error erofs cannot be used in this platform
>> -#endif
>> -
>>  enum erofs_kmap_type {
>>  	EROFS_NO_KMAP,		/* don't map the buffer */
>>  	EROFS_KMAP,		/* use kmap_local_page() to map the buffer */
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index c97615c96ef8..d5fa0f582cbe 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -330,7 +330,6 @@ static int erofs_read_superblock(struct super_block *sb)
>>  	struct erofs_sb_info *sbi;
>>  	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
>>  	struct erofs_super_block *dsb;
>> -	unsigned int blkszbits;
>>  	void *data;
>>  	int ret;
>>  
>> @@ -349,6 +348,17 @@ static int erofs_read_superblock(struct super_block *sb)
>>  		goto out;
>>  	}
>>  
>> +	sbi->blkszbits  = dsb->blkszbits;
>> +	sbi->dirblkbits = dsb->dirblkbits;
>> +	if (sbi->blkszbits < 9 || sbi->blkszbits > PAGE_SHIFT) {
>> +		erofs_err(sb, "blkszbits %u isn't supported", sbi->blkszbits);
>> +		goto out;
>> +	}
>> +	if (sbi->dirblkbits) {
>> +		erofs_err(sb, "dirblkbits %u isn't supported", sbi->dirblkbits);
>> +		goto out;
>> +	}
>> +
>>  	sbi->feature_compat = le32_to_cpu(dsb->feature_compat);
>>  	if (erofs_sb_has_sb_chksum(sbi)) {
>>  		ret = erofs_superblock_csum_verify(sb, data);
>> @@ -357,19 +367,11 @@ static int erofs_read_superblock(struct super_block *sb)
>>  	}
>>  
>>  	ret = -EINVAL;
>> -	blkszbits = dsb->blkszbits;
>> -	/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */
>> -	if (blkszbits != LOG_BLOCK_SIZE) {
>> -		erofs_err(sb, "blkszbits %u isn't supported on this platform",
>> -			  blkszbits);
>> -		goto out;
>> -	}
>> -
>>  	if (!check_layout_compatibility(sb, dsb))
>>  		goto out;
>>  
>>  	sbi->sb_size = 128 + dsb->sb_extslots * EROFS_SB_EXTSLOT_SIZE;
>> -	if (sbi->sb_size > EROFS_BLKSIZ) {
>> +	if (sbi->sb_size > PAGE_SIZE - EROFS_SUPER_OFFSET) {
>>  		erofs_err(sb, "invalid sb_extslots %u (more than a fs block)",
>>  			  sbi->sb_size);
>>  		goto out;
>> @@ -736,8 +738,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>  
>>  	sbi->blkszbits = PAGE_SHIFT;
>>  	if (erofs_is_fscache_mode(sb)) {
>> -		sb->s_blocksize = EROFS_BLKSIZ;
>> -		sb->s_blocksize_bits = LOG_BLOCK_SIZE;
>> +		sb->s_blocksize = PAGE_SIZE;
>> +		sb->s_blocksize_bits = PAGE_SHIFT;
>>  
>>  		err = erofs_fscache_register_fs(sb);
>>  		if (err)
>> @@ -747,8 +749,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>  		if (err)
>>  			return err;
>>  	} else {
>> -		if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
>> -			erofs_err(sb, "failed to set erofs blksize");
>> +		if (!sb_set_blocksize(sb, PAGE_SIZE)) {
>> +			errorfc(fc, "failed to set initial blksize");
>>  			return -EINVAL;
>>  		}
>>  
>> @@ -761,12 +763,24 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>  	if (err)
>>  		return err;
>>  
>> -	if (test_opt(&sbi->opt, DAX_ALWAYS)) {
>> -		BUILD_BUG_ON(EROFS_BLKSIZ != PAGE_SIZE);
>> +	if (sb->s_blocksize_bits != sbi->blkszbits) {
>> +		if (erofs_is_fscache_mode(sb)) {
>> +			errorfc(fc, "unsupported blksize for fscache mode");
>> +			return -EINVAL;
>> +		}
>> +		if (!sb_set_blocksize(sb, 1 << sbi->blkszbits)) {
>> +			errorfc(fc, "failed to set erofs blksize");
>> +			return -EINVAL;
>> +		}
>> +	}
>>  
>> +	if (test_opt(&sbi->opt, DAX_ALWAYS)) {
>>  		if (!sbi->dax_dev) {
>>  			errorfc(fc, "DAX unsupported by block device. Turning off DAX.");
>>  			clear_opt(&sbi->opt, DAX_ALWAYS);
>> +		} else if (sbi->blkszbits != PAGE_SHIFT) {
>> +			errorfc(fc, "unsupported blocksize for DAX");
>> +			clear_opt(&sbi->opt, DAX_ALWAYS);
>>  		}
>>  	}
>>  

Thanks for the review.  I will update all these in the next version.

-- 
Thanks,
Jingbo