linux-ext4 - Re: [PATCH 03/74] mke2fs: load configfile blocksize setting before 64bit checks

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Date:	Thu, 12 Dec 2013 15:28:14 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Theodore Ts'o <tytso@....edu>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [PATCH 03/74] mke2fs: load configfile blocksize setting before 64bit checks


On Dec 10, 2013, at 6:18 PM, Darrick J. Wong <darrick.wong@...cle.com> wrote:

> mke2fs has a series of checks to ensure that we don't create a
> filesystem too big for its blocksize -- if auto-64bit is on, then it
> turns on 64bit; otherwise it complains.  Unfortunately, it performs
> these checks before looking in mke2fs.conf for a blocksize, which
> means that the checks are incorrect if the user specifies a non-4096
> blocksize in the config file and says nothing on the command line.
> The bug also has the effect of mandating a 4k block size on any block
> device larger than 4T in that situation.  Therefore, read the block
> size from the config file before performing the 64bit checks.
> 
> Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
> misc/mke2fs.c |  134 +++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 72 insertions(+), 62 deletions(-)
> 
> 
> diff --git a/misc/mke2fs.c b/misc/mke2fs.c
> index 67c9225..19b6e85 100644
> --- a/misc/mke2fs.c
> +++ b/misc/mke2fs.c
> @@ -1780,15 +1795,67 @@ profile_error:
> 		}
> 	}
> 
> +	/* Get the hardware sector sizes, if available */
> +	retval = ext2fs_get_device_sectsize(device_name, &lsector_size);
> +	if (retval) {
> +		com_err(program_name, retval,
> +			_("while trying to determine hardware sector size"));
> +		exit(1);
> +	}
> +	retval = ext2fs_get_device_phys_sectsize(device_name, &psector_size);
> +	if (retval) {
> +		com_err(program_name, retval,
> +			_("while trying to determine physical sector size"));
> +		exit(1);
> +	}
> +
> +	tmp = getenv("MKE2FS_DEVICE_SECTSIZE");
> +	if (tmp != NULL)
> +		lsector_size = atoi(tmp);
> +	tmp = getenv("MKE2FS_DEVICE_PHYS_SECTSIZE");
> +	if (tmp != NULL)
> +		psector_size = atoi(tmp);
> +
> +	/* Older kernels may not have physical/logical distinction */
> +	if (!psector_size)
> +		psector_size = lsector_size;
> +
> +	if (blocksize <= 0) {
> +		use_bsize = get_int_from_profile(fs_types, "blocksize", 4096);
> +
> +		if (use_bsize == -1) {
> +			use_bsize = sys_page_size;
> +			if ((linux_version_code < (2*65536 + 6*256)) &&

Would be nice to have a helper to compute the linux_version_code comparison,
the above is a bit too much detail for this code.

> +			    (use_bsize > 4096))
> +				use_bsize = 4096;
> +		}
> +		if (lsector_size && use_bsize < lsector_size)
> +			use_bsize = lsector_size;
> +		if ((blocksize < 0) && (use_bsize < (-blocksize)))
> +			use_bsize = -blocksize;
> +		blocksize = use_bsize;
> +		fs_blocks_count /= (blocksize / 1024);
> +	} else {
> +		if (blocksize < lsector_size) {			/* Impossible */
> +			com_err(program_name, EINVAL,
> +				_("while setting blocksize; too small "
> +				  "for device\n"));
> +			exit(1);
> +		} else if ((blocksize < psector_size) &&
> +			   (psector_size <= sys_page_size)) {	/* Suboptimal */
> +			fprintf(stderr, _("Warning: specified blocksize %d is "
> +				"less than device physical sectorsize %d\n"),
> +				blocksize, psector_size);
> +		}
> +	}
> +
> +	fs_param.s_log_block_size =
> +		int_log2(blocksize >> EXT2_MIN_BLOCK_LOG_SIZE);

Does it make sense to wrap this whole block size guessing dance into a small
helper routine, like "figure_fs_blocksize()" or similar?


Cheers, Andreas






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