linux-ext4 - Re: [PATCH 05/10] libext2fs: add pseudo bitmap backend type EXT2FS_BMAP64

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Date:	Mon, 19 Dec 2011 12:16:51 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 05/10] libext2fs: add pseudo bitmap backend type
 EXT2FS_BMAP64_AUTODIR

On Sun, 18 Dec 2011, Theodore Ts'o wrote:

> This backend type will automatically switch between the bitarray and
> the rbtree backend based on the number of directories in the file
> system.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  lib/ext2fs/Makefile.in    |    3 +++
>  lib/ext2fs/ext2fs.h       |    1 +
>  lib/ext2fs/gen_bitmap64.c |    8 ++++++++
>  3 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/lib/ext2fs/Makefile.in b/lib/ext2fs/Makefile.in
> index 4c5ebed..ef55494 100644
> --- a/lib/ext2fs/Makefile.in
> +++ b/lib/ext2fs/Makefile.in
> @@ -400,6 +400,9 @@ check:: tst_bitops tst_badblocks tst_iscan tst_types tst_icount \
>  	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) \
>  		./tst_bitmaps -t 2 -f $(srcdir)/tst_bitmaps_cmds > tst_bitmaps_out
>  	diff $(srcdir)/tst_bitmaps_exp tst_bitmaps_out
> +	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) \
> +		./tst_bitmaps -t 3 -f $(srcdir)/tst_bitmaps_cmds > tst_bitmaps_out
> +	diff $(srcdir)/tst_bitmaps_exp tst_bitmaps_out
>  
>  installdirs::
>  	$(E) "	MKINSTALLDIRS $(libdir) $(includedir)/ext2fs"
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 5ffb036..f2df66e 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -294,6 +294,7 @@ struct struct_ext2_filsys {
>  
>  #define EXT2FS_BMAP64_BITARRAY	1
>  #define EXT2FS_BMAP64_RBTREE	2
> +#define EXT2FS_BMAP64_AUTODIR	3
>  
>  /*
>   * Return flags for the block iterator functions
> diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
> index c9b4051..7b066a2 100644
> --- a/lib/ext2fs/gen_bitmap64.c
> +++ b/lib/ext2fs/gen_bitmap64.c
> @@ -86,6 +86,7 @@ errcode_t ext2fs_alloc_generic_bmap(ext2_filsys fs, errcode_t magic,
>  {
>  	ext2fs_generic_bitmap	bitmap;
>  	struct ext2_bitmap_ops	*ops;
> +	ext2_ino_t num_dirs;
>  	errcode_t retval;
>  
>  	if (!type)
> @@ -98,6 +99,13 @@ errcode_t ext2fs_alloc_generic_bmap(ext2_filsys fs, errcode_t magic,
>  	case EXT2FS_BMAP64_RBTREE:
>  		ops = &ext2fs_blkmap64_rbtree;
>  		break;
> +	case EXT2FS_BMAP64_AUTODIR:
> +		retval = ext2fs_get_num_dirs(fs, &num_dirs);
> +		if (retval || num_dirs > (fs->super->s_inodes_count / 320))
> +			ops = &ext2fs_blkmap64_bitarray;
> +		else
> +			ops = &ext2fs_blkmap64_rbtree;
> +		break;

It is good that even if ext2fs_get_num_dirs() would fail (but it can
not in current implementation - it always return 0), we will set backend
operation struct anyway.

>  	default:
>  		return EINVAL;
>  	}
> 

-- 
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