linux-ext4 - Re: [PATCH] e2fsprogs: Apple Darwin, fix case of device with not 512 bytes block size

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Date:   Sun, 19 Mar 2017 16:45:03 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Fedor Uporov <thisisadrgreenthumb@...il.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2fsprogs: Apple Darwin, fix case of device with not 512
 bytes block size

Thanks for the patch.  Can you tell me how far back support for
DKIOCGETBLOCKSIZE goes?  i.e., is it worth adding a fallback if
DKIOCGETBLOCKSIZE is not available?  I suppose in the worst case we
can fall back to using a binary search to find size of the device.

Also, could I perhaps ask you to take a look at
lib/ext2fs/getsectsize.c while you are at it?  Does Mac OS X have
support for DIOCGSECTORSIZE, and how does this related to
DKIOCGETBLOCKSIZE?  Do you know what Mac OS X's alignment restrictions
are for Direct I/O?

Many thanks for helping me improve Apple Darwin support for e2fsprogs!  :-)

     	    		   	   - Ted

On Sun, Mar 19, 2017 at 10:29:26PM +0300, Fedor Uporov wrote:
> Signed-off-by: Fedor Uporov <thisisadrgreenthumb@...il.com>
> ---
>  lib/blkid/getsize.c  | 11 +++++++----
>  lib/ext2fs/getsize.c |  9 ++++++---
>  2 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/blkid/getsize.c b/lib/blkid/getsize.c
> index 8e8eb4c..3d26338 100644
> --- a/lib/blkid/getsize.c
> +++ b/lib/blkid/getsize.c
> @@ -78,12 +78,15 @@ blkid_loff_t blkid_get_dev_size(int fd)
>  	unsigned long long size64;
>  	blkid_loff_t high, low;
>  
> -#ifdef DKIOCGETBLOCKCOUNT	/* For Apple Darwin */
> -	if (ioctl(fd, DKIOCGETBLOCKCOUNT, &size64) >= 0) {
> +#if defined DKIOCGETBLOCKCOUNT && defined DKIOCGETBLOCKSIZE	/* For Apple Darwin */
> +	unsigned int size;
> +
> +	if (ioctl(fd, DKIOCGETBLOCKCOUNT, &size64) >= 0 &&
> +	    ioctl(fd, DKIOCGETBLOCKSIZE, &size) >= 0) {
>  		if (sizeof(blkid_loff_t) < sizeof(unsigned long long) &&
> -		    (size64 << 9) > 0xFFFFFFFF)
> +		    (size64 * size) > 0xFFFFFFFF)
>  			return 0; /* EFBIG */
> -		return (blkid_loff_t)size64 << 9;
> +		return (blkid_loff_t)size64 * size;
>  	}
>  #endif
>  
> diff --git a/lib/ext2fs/getsize.c b/lib/ext2fs/getsize.c
> index 89c33d4..68480c6 100644
> --- a/lib/ext2fs/getsize.c
> +++ b/lib/ext2fs/getsize.c
> @@ -151,9 +151,12 @@ errcode_t ext2fs_get_device_size2(const char *file, int blocksize,
>  	if (fd < 0)
>  		return errno;
>  
> -#ifdef DKIOCGETBLOCKCOUNT	/* For Apple Darwin */
> -	if (ioctl(fd, DKIOCGETBLOCKCOUNT, &size64) >= 0) {
> -		*retblocks = size64 / (blocksize / 512);
> +#if defined DKIOCGETBLOCKCOUNT && defined DKIOCGETBLOCKSIZE	/* For Apple Darwin */
> +	unsigned int size;
> +
> +	if (ioctl(fd, DKIOCGETBLOCKCOUNT, &size64) >= 0 &&
> +	    ioctl(fd, DKIOCGETBLOCKSIZE, &size) >= 0) {
> +		*retblocks = size64 * size / blocksize;
>  		goto out;
>  	}
>  #endif
> -- 
> 2.1.4
>