linux-kernel - Re: [PATCH 02/16] f2fs: add on-disk layout

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Date:	Sun, 07 Oct 2012 03:25:32 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...il.com>
To:	Martin Steigerwald <Martin@...htvoll.de>
Cc:	linux-kernel@...r.kernel.org,
	±èÀç±Ø <jaegeuk.kim@...sung.com>,
	viro@...iv.linux.org.uk, 'Theodore Ts'o' <tytso@....edu>,
	gregkh@...uxfoundation.org, chur.lee@...sung.com,
	cm224.lee@...sung.com, jooyoung.hwang@...sung.com
Subject: Re: [PATCH 02/16] f2fs: add on-disk layout

2012-10-05 (ê¸ˆ), 19:46 +0200, Martin Steigerwald:
> Am Freitag, 5. Oktober 2012 schrieb ê¹€ìž¬ê·¹:
> > This adds a header file describing the on-disk layout of f2fs.
> > 
> > Signed-off-by: Changman Lee <cm224.lee@...sung.com>
> > Signed-off-by: Chul Lee <chur.lee@...sung.com>
> > Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> > ---
> >  include/linux/f2fs_fs.h |  359 +++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 359 insertions(+)
> >  create mode 100644 include/linux/f2fs_fs.h
> > 
> > diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> > new file mode 100644
> > index 0000000..b17eeec
> > --- /dev/null
> > +++ b/include/linux/f2fs_fs.h
> > @@ -0,0 +1,359 @@
> > +/**
> > + * include/linux/f2fs_fs.h
> [â€¦]
> > +/*
> > + * For superblock
> > + */
> > +struct f2fs_super_block {
> > +       __le32 magic;           /* Magic Number */
> > +       __le16 major_ver;       /* Major Version */
> > +       __le16 minor_ver;       /* Minor Version */
> > +       __le32 log_sectorsize;  /* log2 (Sector size in bytes) */
> > +       __le32 log_sectors_per_block;   /* log2 (Number of sectors per block */
> > +       __le32 log_blocksize;   /* log2 (Block size in bytes) */
> > +       __le32 log_blocks_per_seg; /* log2 (Number of blocks per segment) */
> > +       __le32 log_segs_per_sec; /* log2 (Number of segments per section) */
> > +       __le32 secs_per_zone; /* Number of sections per zone */
> > +       __le32 checksum_offset; /* Checksum position in this super block */
> > +       __le64 block_count;     /* Total number of blocks */
> > +       __le32 section_count;   /* Total number of sections */
> > +       __le32 segment_count;   /* Total number of segments */
> > +       __le32 segment_count_ckpt; /* Total number of segments
> > +                                     in Checkpoint area */
> > +       __le32 segment_count_sit; /* Total number of segments
> > +                                    in Segment information table */
> > +       __le32 segment_count_nat; /* Total number of segments
> > +                                    in Node address table */
> > +       /*Total number of segments in Segment summary area */
> > +       __le32 segment_count_ssa;
> > +       /* Total number of segments in Main area */
> > +       __le32 segment_count_main;
> > +       __le32 failure_safe_block_distance;
> > +       __le64 segment0_blkaddr;        /* Start block address of Segment 0 */
> > +       __le64 start_segment_checkpoint; /* Start block address of ckpt */
> > +       __le64 sit_blkaddr;     /* Start block address of SIT */
> > +       __le64 nat_blkaddr;     /* Start block address of NAT */
> > +       __le64 ssa_blkaddr;     /* Start block address of SSA */
> > +       __le64 main_blkaddr;    /* Start block address of Main area */
> > +       __le32 root_ino;        /* Root directory inode number */
> > +       __le32 node_ino;        /* node inode number */
> > +       __le32 meta_ino;        /* meta inode number */
> > +       __le32 volume_serial_number;    /* VSN is optional field */
> > +       __le16 volume_name[8];  /* Volume Name. 8 unicode characters */
> > +} __packed;
> 
> Any reason why volume label is that short?
> 

Noop.

> If superblock can occupy up to 4096 bytes, i.e. a block, I think a bit
> more space for volume label would fit in there. I count 128 bytes up
> to volume_name. Do other structures need to fit in superblock as well?
> 

I think it cannot be a problem to give more bytes to the name space.
I'll do this.

> I believe users easily can hit a limit of 8 unicode characters even for
> USB sticks and SD cards.

> Nice to see a flash friendly filesystem which seems to take lots of the
> stuff in account I read at Linaro website about flash devices.
> 

Thank you.

-- 
Jaegeuk Kim
Samsung

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