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From:   Andreas Dilger <adilger@dilger.ca>
Message-Id: <1FD80A82-21EF-4BB6-9508-59569112C4D3@dilger.ca>
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Subject: Re: [RFCv1 17/72] libext2fs: Add support for
 ext2fs_test_block_bitmap_range2_valid()
Date:   Wed, 14 Dec 2022 14:21:07 -0700
In-Reply-To: <9015303c19c1b3474d880409db60627b0a9de37f.1667822611.git.ritesh.list@gmail.com>
Cc:     Theodore Ts'o <tytso@mit.edu>, linux-ext4@vger.kernel.org,
        Harshad Shirwadkar <harshadshirwadkar@gmail.com>,
        Wang Shilong <wangshilong1991@gmail.com>, Li Xi <lixi@ddn.com>
To:     "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
References: <cover.1667822611.git.ritesh.list@gmail.com>
 <9015303c19c1b3474d880409db60627b0a9de37f.1667822611.git.ritesh.list@gmail.com>
Precedence: bulk


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On Nov 7, 2022, at 5:21 AM, Ritesh Harjani (IBM) <ritesh.list@gmail.com> =
wrote:
>=20
> From: Wang Shilong <wshilong@ddn.com>
>=20
> This adds the support in libext2fs to query whether the block range is
> valid or not (within range) given the block bitmap.
> Also to avoid duplicate warning messages in case of invalid blocks.
>=20
> This will be later used in pass1 of e2fsck is_blocks_used() function =
to
> check whether the given block range is valid or not to avoid duplicate
> warning resulting from ext2fs_test_block_bitmap_range2()
>=20
> Signed-off-by: Wang Shilong <wshilong@ddn.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

I don't think this patch is correct?

> ---
> diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
> index c31f942f..a9637cb5 100644
> --- a/lib/ext2fs/gen_bitmap64.c
> +++ b/lib/ext2fs/gen_bitmap64.c
> @@ -731,6 +731,39 @@ int =
ext2fs_test_block_bitmap_range2(ext2fs_block_bitmap gen_bmap,
> 	return bmap->bitmap_ops->test_clear_bmap_extent(bmap, block, =
num);
> }
>=20
> +int ext2fs_test_block_bitmap_range2_valid(ext2fs_block_bitmap bitmap,
> +					  blk64_t block, unsigned int =
num)
> +{
> +	ext2fs_generic_bitmap_64 bmap =3D =
(ext2fs_generic_bitmap_64)bitmap;
> +	__u64	end =3D block + num;
> +
> +	if (!bmap)
> +		return 0;
> +
> +	if (EXT2FS_IS_32_BITMAP(bmap)) {
> +		if ((block & ~0xffffffffULL) ||
> +		    ((block+num-1) & ~0xffffffffULL)) {
> +			return 0;
> +		}
> +	}

This is bailing out early if the requested bit is > 2^32, but that is
before cluster conversion below.  However, I think the bitmap is =
actually
stored in clusters, so the 2^32 check seems premature?

> +
> +	if (!EXT2FS_IS_64_BITMAP(bmap))
> +		return 0;
> +
> +	/* convert to clusters if necessary */
> +	block >>=3D bmap->cluster_bits;
> +	end +=3D (1 << bmap->cluster_bits) - 1;
> +	end >>=3D bmap->cluster_bits;
> +	num =3D end - block;
> +
> +	if ((block < bmap->start) || (block > bmap->end) ||
> +	    (block+num-1 > bmap->end))
> +		return 0;
> +
> +	return 1;
> +}

Cheers, Andreas


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